Sustainability measurement is a term that denotes the measurements used as the quantitative basis for the informed management of sustainability.[1] The metrics used for the measurement of sustainability (involving the sustainability of environmental, social and economic domains, both individually and in various combinations) are still evolving: they include indicators, benchmarks, audits, indexes and accounting, as well as assessment, appraisal[2] and other reporting systems. They are applied over a wide range of spatial and temporal scales.[3][4]
From an environmental perspective sustainability measurement can be regarded as a quantitative aspect of resource management that compares the demand on ecosystem services with the available supply.[5]
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The principal objective of sustainability indicators is to inform public policy-making as part of the process of sustainability governance. [6] Sustainability indicators can provide information on any aspect of the interplay between the environment and socio-economic activities. [7] Building strategic indicator sets generally deals with just a few simple questions: what is happening? (descriptive indicators), does it matter and are we reaching targets? (performance indicators), are we improving? (efficiency indicators), are measures working? (policy effectiveness indicators), and are we generally better off? (total welfare indicators). One popular general framework used by The European Environment Agency uses a slight modification of the Organisation for Economic Cooperation and Development DPSIR system.[8] This breaks up environmental impact into five stages. Social and economic developments (consumption and production) (D)rive or initiate environmental (P)ressures which, in turn, produces a change in the (S)tate of the environment which leads to (I)mpacts of various kinds. Societal (R)esponses (policy guided by sustainability indicators) can be introduced at any stage of this sequence of events.
The United Nations has developed extensive sustainability measurement tools in relation to sustainable development [9] as well as a System of Integrated Environmental and Economic Accounting. [10]
In the last couple of decades there has arisen a crowded toolbox of quantitative methods used to assess sustainability — including measures of resource use like life cycle assessment, measures of consumption like the ecological footprint and measurements of quality of environmental governance like the Environmental Performance Index. The following is a list of quantitative "tools" used by sustainability scientists - the different categories are for convenience only as defining criteria will intergrade. It would be too difficult to list all those methods available at different levels of organisation so those listed here are at for the global level only.
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Many environmental problems ultimately relate to the human effect on those global biogeochemical cycles that are critical to life. Over the last decade monitoring these cycles has become a more urgent target for research:
Part of this process can relate to resource use such as energy accounting or to economic metrics or price system values as compared to non-market economics potential, for understanding resource use.[21] An important task for resource theory (energy economics) is to develop methods to optimize resource conversion processes.[22] These systems are described and analyzed by means of the methods of mathematics and the natural sciences.[23] Human factors, however, have dominated the development of our perspective of the relationship between nature and society since at least the Industrial Revolution, and in particular have influenced how we describe and measure the economic impacts of changes in resource quality. A balanced view of these issues requires an understanding of the physical framework in which all human ideas, institutions, and aspirations must operate. [24]
When oil production first began in the mid-nineteenth century, the largest oil fields recovered fifty barrels of oil for every barrel used in the extraction, transportation and refining. This ratio is often referred to as the Energy Return on Energy Investment (EROI or EROEI). Currently, between one and five barrels of oil are recovered for each barrel-equivalent of energy used in the recovery process. As the EROEI drops to one, or equivalently the Net energy gain falls to zero, the oil production is no longer a net energy source. This happens long before the resource is physically exhausted.
Note that it is important to understand the distinction between a barrel of oil, which is a measure of oil, and a barrel of oil equivalent (BOE), which is a measure of energy. Many sources of energy, such as fission, solar, wind, and coal, are not subject to the same near-term supply restrictions that oil is. Accordingly, even an oil source with an EROEI of 0.5 can be usefully exploited if the energy required to produce that oil comes from a cheap and plentiful energy source. Availability of cheap, but hard to transport, natural gas in some oil fields has led to using natural gas to fuel enhanced oil recovery. Similarly, natural gas in huge amounts is used to power most Athabasca Tar Sands plants. Cheap natural gas has also led to Ethanol fuel produced with a net EROEI of less than 1, although figures in this area are controversial because methods to measure EROEI are in debate.
Insofar as economic growth is driven by oil consumption growth, post-peak societies must adapt. M. King Hubbert believed [9]:
| “ | Our principal constraints are cultural. During the last two centuries we have known nothing but exponential growth and in parallel we have evolved what amounts to an exponential-growth culture, a culture so heavily dependent upon the continuance of exponential growth for its stability that it is incapable of reckoning with problems of nongrowth. | ” |
Some economists describe the problem as uneconomic growth or a false economy. At the political right, Fred Ikle has warned about "conservatives addicted to the Utopia of Perpetual Growth" [10]. Brief oil interruptions in 1973 and 1979 markedly slowed - but did not stop - the growth of world GDP [11].
Between 1950 and 1984, as the Green Revolution transformed agriculture around the globe, world grain production increased by 250%. The energy for the Green Revolution was provided by fossil fuels in the form of fertilizers (natural gas), pesticides (oil), and hydrocarbon fueled irrigation.[25]
David Pimentel, professor of ecology and agriculture at Cornell University, and Mario Giampietro, senior researcher at the National Research Institute on Food and Nutrition (INRAN), place in their study Food, Land, Population and the U.S. Economy the maximum U.S. population for a sustainable economy at 200 million. To achieve a sustainable economy world population will have to be reduced by two-thirds, says the study.[26] Without population reduction, this study predicts an agricultural crisis beginning in 2020, becoming critical c. 2050. The peaking of global oil along with the decline in regional natural gas production may precipitate this agricultural crisis sooner than generally expected. Dale Allen Pfeiffer claims that coming decades could see spiraling food prices without relief and massive starvation on a global level such as never experienced before.[27][28]
Although Hubbert peak theory receives most attention in relation to peak oil production, it has also been applied to other natural resources.
Doug Reynolds predicted in 2005 that the North American peak would occur in 2007.[29] Bentley (p.189) predicted a world "decline in conventional gas production from about 2020".[30]
Peak coal is significantly further out than peak oil, but we can observe the example of anthracite in the USA, a high grade coal whose production peaked in the 1920s. Anthracite was studied by Hubbert, and matches a curve closely.[31] Pennsylvania's coal production also matches Hubbert's curve closely, but this does not mean that coal in Pennsylvania is exhausted--far from it. If production in Pennsylvania returned at its all time high, there are reserves for 190 years. Hubbert had recoverable coal reserves worldwide at 2500 × 109 metric tons and peaking around 2150(depending on usage).
More recent estimates suggest an earlier peak. Coal: Resources and Future Production (PDF 630KB[12]), published on April 5 2007 by the Energy Watch Group (EWG), which reports to the German Parliament, found that global coal production could peak in as few as 15 years [13]. Reporting on this Richard Heinberg also notes that the date of peak annual energetic extraction from coal will likely come earlier than the date of peak in quantity of coal (tons per year) extracted as the most energy-dense types of coal have been mined most extensively [14]. A second study, The Future of Coal by B. Kavalov and S. D. Peteves of the Institute for Energy (IFE), prepared for European Commission Joint Research Centre, reaches similar conclusions and states that ""coal might not be so abundant, widely available and reliable as an energy source in the future".[15].
Work by David Rutledge of Caltech predicts that the total of world coal production will amount to only about 450 gigatonnes.[32] This implies that coal is running out faster than usually assumed.
Finally, insofar as global peak oil and peak in natural gas are expected anywhere from imminently to within decades at most, any increase in coal production (mining) per annum to compensate for declines in oil or NG production, would necessarily translate to an earlier date of peak as compared with peak coal under a scenario in which annual production remains constant.
In a paper in 1956 [16], after a review of US fissionable reserves, Hubbert notes of nuclear power:
| “ | There is promise, however, provided mankind can solve its international problems and not destroy itself with nuclear weapons, and provided world population (which is now expanding at such a rate as to double in less than a century) can somehow be brought under control, that we may at last have found an energy supply adequate for our needs for at least the next few centuries of the "foreseeable future." | ” |
Technologies such as the thorium fuel cycle, reprocessing and fast breeders can, in theory, considerably extend the life of uranium reserves. Roscoe Bartlett claims [17]
| “ | Our current throwaway nuclear cycle uses up the world reserve of low-cost uranium in about 20 years. | ” |
Caltech physics professor David Goodstein has stated [18] that
| “ | ... you would have to build 10,000 of the largest power plants that are feasible by engineering standards in order to replace the 10 terawatts of fossil fuel we're burning today ... that's a staggering amount and if you did that, the known reserves of uranium would last for 10 to 20 years at that burn rate. So, it's at best a bridging technology ... You can use the rest of the uranium to breed plutonium 239 then we'd have at least 100 times as much fuel to use. But that means you're making plutonium, which is an extremely dangerous thing to do in the dangerous world that we live in. | ” |
Hubbert applied his theory to "rock containing an abnormally high concentration of a given metal"[33] and reasoned that the peak production for metals such as copper, tin, lead, zinc and others would occur in the time frame of decades and iron in the time frame of two centuries like coal. The price of copper rose 500% between 2003 and 2007[34] was by some attributed to peak copper.[35][36] Copper prices later fell, along with many other commodities and stock prices, as demand shrank from fear of a global recession.[37] Lithium availability is a concern for a fleet of Li-ion battery using cars but a paper published in 1996 estimated that world reserves are adequate for at least 50 years [19]. A similar prediction [20] for platinum use in fuel cells notes that the metal could be easily recycled.
Phosphorus supplies are essential to farming and depletion of reserves is estimated at somewhere from 60 to 130 years [21]. Individual countries supplies vary widely; without a recycling initiative America's supply [22] is estimated around 30 years [23]. Phosphorus supplies affect total agricultural output which in turn limits alternative fuels such as biodiesel and ethanol.
Hubbert's original analysis did not apply to renewable resources. However over-exploitation often results in a Hubbert peak nonetheless. A modified Hubbert curve applies to any resource that can be harvested faster than it can be replaced.[38]
For example, a reserve such as the Ogallala Aquifer can be mined at a rate that far exceeds replenishment. This turns much of the world's underground water [24] and lakes [25] into finite resources with peak usage debates similar to oil. These debates usually center around agriculture and suburban water usage but generation of electricity [26] from nuclear energy or coal and tar sands mining mentioned above is also water resource intensive. The term fossil water is sometimes used to describe aquifers whose water is not being recharged.
The last glacial period was the most recent glacial period within the current ice age occurring during the Pleistocene from ~110,000—10,000 years ago, a period of ~.[1]
During this period there were several changes between glacier advance
and retreat. The maximum extent of glaciation
was approximately 18,000 years ago. While the general pattern of global
cooling and glacier advance was similar, local differences in the
development of glacier advance and retreat make it difficult to compare
the details from continent to continent (see picture of ice core data
below for differences).
The last glacial period is sometimes colloquially referred to as the "last ice age", though this use is incorrect because an ice age is a longer period of cold temperature in which ice sheets cover large parts of the Earth, such as Antarctica. Glacials, on the other hand, refer to colder phases within an ice age that separate interglacials. Thus, the end of the last glacial period is not the end of the last ice age. The end of the last glacial period was about 12,500 years ago, while the end of the last ice age may not yet have come: little evidence points to a stop of the glacial-interglacial cycle of the last million years.
The last glacial period is the best-known part of the current ice age, and has been intensively studied in North America, northern Eurasia, the Himalaya and other formerly glaciated regions around the world. The glaciations that occurred during this glacial period covered many areas, mainly on the Northern Hemisphere and to a lesser extent on the Southern Hemisphere. They have different names, historically developed and depending on their geographic distributions: Fraser (in the Pacific Cordillera of North America), Pinedale, Wisconsinan or Wisconsin (in central North America), Devensian (in the British Isles), Midlandian (in Ireland), Würm (in the Alps), Merida (in Venezuela), Weichselian (in Scandinavia and Northern Europe), Vistulian (in northern Central Europe), Valdai in Eastern Europe and Zyryanka in Siberia, Llanquihue in Chile, and Otira in New Zealand.
The last glaciation centered on the huge ice sheets of North America and Eurasia. Considerable areas in the Alps, the Himalaya and the Andes were ice-covered, and Antarctica remained glaciated.
Canada was nearly completely covered by ice, as well as the northern part of the USA, both blanketed by the huge Laurentide ice sheet. Alaska remained mostly ice free due to arid climate conditions. Local glaciations existed in the Rocky Mountains, the Cordilleran ice sheet and as ice fields and ice caps in the Sierra Nevada in northern California.[2] In Britain, mainland Europe and northwestern Asia, the Scandinavian ice sheet once again reached the northern parts of the British Isles, Germany, Poland and Russia, extending as far east as the Taimyr Peninsula in western Siberia.[3] Maximum extent of western Siberian glaciation was approximately 18,000 to 17,000 BP and thus later than in Europe (22,000–18,000 BP).[4] Northeastern Siberia was not covered by a continental-scale ice sheet.[5] Instead, large, but restricted, icefield complexes covered mountain ranges within northeast Siberia, including the Kamchatka-Koryak Mountains.[6]
The Arctic Ocean between the huge ice sheets of America and Eurasia was not frozen throughout, but like today probably was only covered by relatively thin ice, subject to seasonal changes and riddled with icebergs calving from the surrounding ice sheets. According to the sediment composition retrieved from deep-sea cores there must even have been times of seasonally open waters.[7]
Outside the main ice sheets widespread glaciation occurred on the Alps-Himalaya mountain chain. In contrast to the earlier glacial stages the Würm glaciation was composed of smaller ice caps and mostly confined to valley glaciers, sending glacial lobes into the Alpine forland. To the east the Caucasus and the mountains of Turkey and Iran were capped by local ice fields or small ice sheets.[8],[9] In the Himalaya and the Tibetan Plateau glaciers advanced considerably, particularly between 47,000–27,000 BP[10] and in contrast to the widespread contemporaneous warming elsewhere.[11] The formation of a contiguous ice sheet on the Tibetan Plateau is controversial.[12]
Other areas of the Northern Hemisphere did not bear extensive ice sheets but local glaciers in high areas. Parts of Taiwan for example were repeatedly glaciated between 44,250 and 10,680 BP[13] as well as the Japanese Alps. In both areas maximum glacier advance occurred between 60,000 and 30,000 BP.[14] To a still lesser extent glaciers existed in Africa, for example in the High Atlas, the mountains of Morocco, the Mount Atakor massif in southern Algeria and several mountains in Ethiopia. In the Southern Hemisphere, an ice cap of several hundred square kilometers was present on the east African mountains in the Kilimanjaro Massif, Mount Kenya and the Ruwenzori Mountains, still bearing remnants of glaciers today.[15]
Glaciation of the Southern Hemisphere was less extensive because of current configuration of continents. Ice sheets existed in the Andes (Patagonian Ice Sheet), where six glacier advances between 33,500 and 13,900 BP in the Chilean Andes have been reported.[16] Antarctica was entirely glaciated, much like today, but the ice sheet left no uncovered area. In mainland Australia only a very small area in the vicinity of Mount Kosciuszko was glaciated, whereas in Tasmania glaciation was more widespread.[17] New Zealand saw a glaciation in the New Zealand Alps, where at least three glacier advances can be distinguished.[18] Local ice caps existed in Irian Jaya, Indonesia, where in three ice areas remnants of the Pleistocene glaciers are still preserved today.[19]
The Pinedale (central Rocky Mountains) or Fraser (Cordilleran ice sheet) glaciation was the last of the major glaciations to appear in the Rocky Mountains in the United States. The Pinedale lasted from approximately 30,000 to 10,000 years ago and was at its greatest extent between 23,500 and 21,000 years ago. [20] This glaciation was somewhat distinct from the main Wisconsin glaciation as it was only loosely related to the giant ice sheets and was instead composed of mountain glaciers, merging into the Cordilleran Ice Sheet.[21] The Cordilleran ice sheet produced features such as glacial Lake Missoula, which would break free from its ice dam causing the massive Missoula floods. Geologists estimate that the cycle of flooding and reformation of the lake lasted on average of 55 years and that the floods occurred approximately 40 times over the 2,000 year period between 15,000 and 13,000 years ago.[22] Glacial lake outburst floods such as these are not uncommon today in Iceland and other places.
The Wisconsin Glacial Episode was the last major advance of continental glaciers in the North American Laurentide ice sheet. This glaciation is made of three glacial maxima (sometimes mistakenly called ice ages) separated by interglacial warm periods (such as the one we are living in). These glacial maxima are called, from oldest to youngest, Tahoe, Tenaya and Tioga. The Tahoe reached its maximum extent perhaps about 70,000 years ago, perhaps as a byproduct of the Toba super eruption. Little is known about the Tenaya. The Tioga was the least severe and last of the Wisconsin Episode. It began about 30,000 years ago, reached its greatest advance 21,000 years ago, and ended about 10,000 years ago. At the height of glaciation the Bering land bridge permitted migration of mammals such as humans to North America from Siberia.
It radically altered the geography of North America north of the Ohio River. At the height of the Wisconsin Episode glaciation, ice covered most of Canada, the Upper Midwest, and New England, as well as parts of Montana and Washington. On Kelleys Island in Lake Erie or in New York's Central Park, the grooves left by these glaciers can be easily observed. In southwestern Saskatchewan and southeastern Alberta a suture zone between the Laurentide and Cordilleran ice sheets formed the Cypress Hills, which is the northernmost point in North America that remained south of the continental ice sheets.
The Great Lakes are the result of glacial scour and pooling of meltwater at the rim of the receding ice. When the enormous mass of the continental ice sheet retreated, the Great Lakes began gradually moving south due to isostatic rebound of the north shore. Niagara Falls is also a product of the glaciation, as is the course of the Ohio River, which largely supplanted the prior Teays River.
With the assistance of several very large glacial lakes, it carved the gorge now known as the Upper Mississippi River, filling into the Driftless Area and probably creating an annual ice-dam-burst.
In its retreat, the Wisconsin Episode glaciation left terminal moraines that form Long Island, Block Island, Cape Cod, Nomans Land, Marthas Vineyard, and Nantucket, and the Oak Ridges Moraine in south central Ontario, Canada. In Wisconsin itself, it left the Kettle Moraine. The drumlins and eskers formed at its melting edge are landmarks of the Lower Connecticut River Valley.
In Northwest Greenland, ice coverage attained a very early maximum in the last glacial period around 114,000. After this early maximum, the ice coverage was similar to today until the end of the last glacial period. Towards the end glaciers readvanced once more before retreating to their present extent.[23] According to ice core data, the Greenland climate was dry during the last glacial period, precipitation reaching perhaps only 20% of today's value. [24]
The name Devensian glaciation is used by British geologists and archaeologists and refers to what is often popularly meant by the latest Ice Age. Irish geologists, geographers and archaeologists refer to the Midlandian glaciation as its effects in Ireland are largely visible in the Irish midlands.
The effects of this glaciation can be seen in many geological features of England, Wales, Scotland, and Northern Ireland. Its deposits have been found overlying material from the preceding Ipswichian Stage and lying beneath those from the following Flandrian stage of the Holocene.
The latter part of the Devensian includes Pollen zones I-IV, the Allerød, and Bølling Oscillations and the Older and Younger Dryas climatic stages.
Alternative names include: Weichsel or Vistulian glaciation (named after the Polish river Vistula or its German name Weichsel). During the glacial maximum in Scandinavia, only the western parts of Jutland were ice-free, and a large part of what is today the North Sea was dry land connecting Jutland with Britain. It is also in Denmark that the only Scandinavian ice-age animals older than 13,000 BC are found.[citation needed] In the period following the last interglacial before the current one (Eemian Stage), the coast of Norway was also ice-free.
The Baltic Sea, with its unique brackish water, is a result of meltwater from the Weichsel glaciation combining with saltwater from the North Sea when the straits between Sweden and Denmark opened. Initially, when the ice began melting about 10,300 ybp, seawater filled the isostatically depressed area, a temporary marine incursion that geologists dub the Yoldia Sea. Then, as post-glacial isostatic rebound lifted the region about 9500 ybp, the deepest basin of the Baltic became a freshwater lake, in palaeological contexts referred to as Ancylus Lake, which is identifiable in the freshwater fauna found in sediment cores. The lake was filled by glacial runoff, but as worldwide sea level continued rising, saltwater again breached the sill about 8000 ybp, forming a marine Littorina Sea which was followed by another freshwater phase before the present brackish marine system was established. "At its present state of development, the marine life of the Baltic Sea is less than about 4000 years old," Drs. Thulin and Andrushaitis remarked when reviewing these sequences in 2003.
Overlaying ice had exerted pressure on the Earth's surface. As a result of melting ice, the land has continued to rise yearly in Scandinavia, mostly in northern Sweden and Finland where the land is rising at a rate of as much as 8–9 mm per year, or 1 meter in 100 years. This is important for archaeologists since a site that was coastal in the Nordic Stone Age now is inland and can be dated by its relative distance from the present shore.
The term Würm is derived from a river in the Alpine foreland, approximately marking the maximum glacier advance of this particular glacial period. The Alps have been the area where first systematic scientific research on ice ages has been conducted by Louis Agassiz in the beginning of the 19th century. Here the Würm glaciation of the last glacial period was intensively studied. Pollen analysis, the statistical analyses of microfossilized plant pollens found in geological deposits, has chronicled the dramatic changes in the European environment during the Würm glaciation. During the height of Würm glaciation, ca 24,000–10,000 ybp, most of western and central Europe and Eurasia was open steppe-tundra, while the Alps presented solid ice fields and montane glaciers. Scandinavia and much of Britain were under ice.
During the Würm, the Rhône Glacier covered the whole western Swiss plateau, reaching today's regions of Solothurn and Aarau. In the region of Bern it merged with the Aar glacier. The Rhine Glacier is currently the subject of the most detailed studies. Glaciers of the Reuss and the Limmat advanced sometimes as far as the Jura. Montane and piedmont glaciers formed the land by grinding away virtually all traces of the older Günz and Mindel glaciation, by depositing base moraines and terminal moraines of different retraction phases and loess deposits, and by the pro-glacial rivers' shifting and redepositing gravels. Beneath the surface, they had profound and lasting influence on geothermal heat and the patterns of deep groundwater flow.
The name Merida Glaciation is proposed to designate the alpine glaciation which affected the central Venezuelan Andes; during the Late Pleistocene. Two main moraine levels have been recognized: one between 2600 and 2700 m, and another between 3000 and 3500 m elevation. The snow line during the last glacial advance was lowered approximately 1200 m below the present snow line (3700 m). The glaciated area in the Cordillera de Mérida was approximately 600 km2; this included the following high areas from southwest to northeast: Páramo de Tamá, Páramo Batallón, Páramo Los Conejos, Páramo Piedras Blancas, and Teta de Niquitao. Approximately 200 km2 of the total glaciated area was in the Sierra Nevada de Mérida, and of that amount, the largest concentration, 50 km2, was in the areas of Pico Bolívar, Pico Humboldt (4,942 m), and Pico Bonpland (4,893 m). Radiocarbon dating indicates that the moraines are older than 10,000 years B.P., and probably older than 13,000 years B.P. The lower moraine level probably corresponds to the main Wisconsin glacial advance. The upper level probably represents the last glacial advance (Late Wisconsin).[25][26][27][28]
The Llanquihue glaciation takes its name from Llanquihue Lake in southern Chile which is a fan-shaped piedmont glacial lake. On the lake's western shores there are large moraine systems of which the innermost belong to the last glacial period. Llanquihue Lake's varves are a node point in southern Chile's varve geochronology. During the last glacial maximum the Patagonian Ice Sheet extended over the Andes from about 35°S to Tierra del Fuego at 55°S. The western part appears to have been very active, with wet basal conditions, while the eastern part was cold based. Palsas seems to have developed at least in the unglaciated parts of Isla Grande de Tierra del Fuego. The area west of Llanquihue Lake was ice-free during the LGM, and had sparsely distributed vegetation dominated by Nothofagus. Valdivian temperate rainforest extended continuously as far north as to Bosque de Fray Jorge National Park, the forest currently found there are relicts from the Last glacial period.
During the last glacial period Antarctica was blanketed by a massive ice sheet, much like it is today. The ice covered all land areas and extended into the ocean onto the middle and outer continental shelf[29][30]. According to ice modelling, ice over central East Antarctica was generally thinner than today.[31]
| Smilodon Fossil range: Late Pliocene to Late Pleistocene |
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|---|---|
 |
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| Smilodon californicus fossil at the National Museum of Natural History, Washington, DC | |
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Carnivora |
| Family: | Felidae |
| Subfamily: | Machairodontinae |
| Genus: | Smilodon Lund, 1842 |
| Species | |
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S. fatalis |
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Smilodon (pronounced /ˈsmаɪlədɵn/), often called saber-toothed cat or saber-toothed tiger, is an extinct genus of the subfamily machairodontine[1] saber-toothed cats endemic to North America and South America living from the Early Pleistocene through Lujanian stage of the Pleistocene epoch (1.8 mya—10,000 years ago).
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They are called "saber-toothed" for the extreme length of their maxillary canines. Despite the colloquial name of "saber-toothed tiger", Smilodon is not a tiger. Tigers belong to the subfamily Pantherinae. The name Smilodon is a bahuvrihi from Greek: σμίλη, smilē, "chisel" and Greek ὀδoύς (odoús), "tooth", Genitive: ὀδoύς, ὀδόντος,odóntos.
The genus Smilodon was described by the Danish naturalist and palaeontologist Peter Wilhelm Lund in 1841. He found the fossils of Smilodon populator in caves near the small town of Lagoa Santa, in the state of Minas Gerais, Brazil.
A number of Smilodon species have been described, but today usually only three are recognized.[2]
They are among the largest felids; the heaviest specimens of the massively built carnivore S. populator may have exceeded 400 kg (880 lb).[3]
A fully-grown Smilodon weighed approximately 55 to 400 kg (120 to 880 lb), depending on species. It had a short tail, powerful legs, muscular neck and long canines. Smilodon was more robustly built than any modern cat, comparable to a bear. The lumbar region of the back was proportionally short and the lower limbs were shortened relative to the upper limbs in comparison with modern pantherine cats, suggesting that Smilodon was less of a fast runner.
The largest species, South American S. populator, had higher shoulders than hips and a back that sloped downwards, superficially recalling the shape of a hyaena, in contrast to the level backed appearance of S. fatalis which was more like that of modern cats. However, while its front limbs were relatively long, their proportions were extremely robust and the forearm was shorter relative to the upper arm bone than in modern big cats, and proportionally even shorter than in S. fatalis. This indicates that these front limbs were designed for power rather than fast running, and S. populator would have had immense strength in its forequarters.
Smilodon had relatively shorter
and more massive limbs than other felines. It had well developed flexors and extensors in its forepaws,[citation needed] which
enabled it to pull down large prey. The back limbs had powerfully built
adductor
muscles which might have helped the cat's stability when wrestling with
prey. Like most cats, its claws were retractable.
Smilodon is most famous for its relatively long canines. They are the longest canines of the saber-toothed cats at about 28 cm (11 in) long in the largest species Smilodon populator. They were probably built more for stabbing than slashing. Despite being more powerfully built than other large cats, Smilodon actually had a weaker bite. Modern big cats have more pronounced zygomatic arches, while Smilodon had smaller zygomatic arches which restricted the thickness and therefore power of the temporalis muscles, and thus reduced Smilodon’s bite force. Analysis of its narrow jaws indicates that it could produce a bite only a third as strong as that of a lion.[4] There seems to a be a general rule that the saber-toothed cats with the largest canines had proportionally weaker bites. However, analyses of canine bending strength (the ability of the canine teeth to resist bending forces without breaking) and bite forces indicate that saber-toothed cats' teeth were stronger relative to the bite force than those of modern "big cats".[5] In addition, Smilodon could open its jaws 120 degrees, whereas the lion can only open its jaws to 65 degrees.
It has been suggested that smilodon's smaller temporalis muscles, (controling much of the bite force) was not used in the killing prey, but rather, the immense strength of the neck of smilodon allowed it to stretch its jaws around the throat and press its canines into the prey with the usage of such immense neck and forelimb muscles rather than an actual bite: the penetration was the result of the neck flexors instead of the jaw muscles, as according to this hypothesis.
The social pattern of this cat is unknown. It has been suggested, based on the abundance of S. fatalis fossils in proportion to prey animals trapped in the La Brea tar-pits,[6] that they were packs of scavengers, lured in by the distress calls of trapped prey. This possibility was tested in 2008 by Chris Carbone (of the Zoological Society of London), who documented the responses of African predators of the Serengeti and Kruger National Park to recorded distress calls of prey species; it was determined that playbacks of prey sounds attract social carnivores, but not solitary hunters.[7] Additionally, some fossils show healed injuries or diseases that would have crippled the animal. Some palaeontologists see this as evidence that saber-toothed cats were social animals, living and hunting in packs that provided food for old and sick members. Living in groups might also allow more effective competition with social lions and wolves. The canine teeth and body size of Smilodon were about the same in both male and female cats. This suggests that one theory about their teeth – that they were used by males to attract mates – is incorrect.
Smilodon probably preyed on a wide variety of large game including bison, deer, American camels, horses and ground sloths. As it is known for the saber-toothed cat Homotherium, Smilodon might have killed also juvenile mastodons and mammoths. The La Brea tar pits in California trapped hundreds of Smilodon in the tar, possibly as they tried to feed on mammoths already trapped. The Natural History Museum of Los Angeles County has many of their complete skeletons.
Modern big cats kill mainly by crushing the windpipe of their victims, which may take a few minutes. Smilodon’s jaw muscles were probably too weak for this and its long canines and fragile skull would have been vulnerable to snapping in a prolonged struggle or when biting a running prey. Research in 2007 concluded that Smilodon more probably used its great upper-body strength to wrestle prey to the ground, where its long canines could deliver a deep stabbing bite to the throat which would generally cut through the jugular vein and / or the trachea and thus kill the prey very quickly.[8] The leaders of this study also commented to scientific journalists that this technique may have made Smilodon a more efficient killer of large prey than modern lions or tigers, but also made it more dependent on the supply of large animals. This highly-specialized hunting style may have contributed to its extinction, as Smilodon’s cumbersome build and over-sized canines would have made it less efficient at killing smaller, faster prey if the ecosystem changed for any reason.[4]
Research upon which African carnivores response to playback of animals in distress has been used to analyse the finds of animal species and their numbers at the La Brea Tar Pits. Such playbacks find animal distress calls such as would come from animal trapped in the tar pit would attract pack hunters such as lions and spotted hyenas, not lone hunters. Given the carnivores found at tar pits were predominately Smilodon and the social dire wolf, this suggests that the former like the latter was also a social animal.[9] One expert, who found the study convincing, further speculated that if that was the case, then Smilodon's exaggerated canine teeth might have been used more for social or sexual signaling than hunting.[10][Full citation needed] However, the lack of sexual dimorphism in the canine teeth refutes this proposal.
Smilodon became extinct around 10,000 BC, a time which saw the extinction of many other large herbivorous and carnivorous mammals.
Prehistoric humans, who reached North America at the end of the Ice age, are often viewed as responsible for this extinction wave. Others have suggested that the end of the ice age caused the extinction. As the ice age ended there would have been shrinking environments and changing vegetation patterns. Extensive grasslands, with different types of grasses, and isolated forests replaced healthy mixes of forests and grasslands. The summer and winter both became more extreme and North America began to dry out or began to be covered in snow, thus denying food sources for mammoths and in turn Smilodon. However, this hypothesis does not explain how Smilodon and its ancestors successfully survived many previous interglacials.
Smilodon appears in various kinds in popular culture.
Several Smilodon appear in the animated film Ice Age, most notably Diego (voiced by Denis Leary), one of the main characters, who also appears in the sequels, Ice Age 2: The Meltdown and Ice Age: Dawn of the Dinosaurs.
In the first two seasons of the children television series Mighty Morphin Power Rangers, the Saber-Toothed Tiger was the inspiration for the Zord of the Yellow Ranger, Trini Kwan.
In the 1977 movie Sinbad and the Eye of the Tiger, the climax takes place in the citadel of a giant Smilodon.
The movie Sabretooth featured a Smilodon that was brought back to life from fossilized DNA.
Smilodon has appeared also as one of the main creatures of Impossible Pictures films Walking With Beasts and Prehistoric Park (fourth episode). The former depicts Smilodon as living and hunting in groups like lions, but the latter depicts them hunting Toxodon alone. The Smilodon appearing in these two were not the same species however, as Smilodon populator appears in Walking With Beasts and Smilodon gracilis appears in Prehistoric Park.
Smilodon fatalis appears in the BBC documentary; Monsters We Met and another documentary; Wild New World.
Smilodon was also featured in the ITVseries Primeval, seen in episode 9. A character finds a young Smilodon cub after it stumbled into an anomaly (portal in time). She raised it from a young age, keeping it hidden from the outside world in her house in the forest. However, once the Smilodon grew to a significant size, it escaped and attacked visitors at a nearby amusement park. The character was later mauled to death by the animal. It also appeared in Prehistoric Predators. Grune The Destroyer, the ghost warrior, from the highly popular classic animated series Thundercats is an anthropomorphic Saber-toothed cat, villain and former Thundercat.
A new monster named "Smilodon" was added in the MMORPG Final Fantasy XI expansion Wings of the Goddess. It is a member of the Tiger family, all of which more closely resemble saber-toothed cats than modern-day tigers.[11]
Jeff Rovin's novel Fatalis is based around a family of sabre-toothed cats coming into a conflict with humans in modern-day Southern California.
In 1971 a Smilodon skeleton was discovered in downtown Nashville, Tennessee during construction of the First American National Bank building, now the Regions Center (Nashville).[12] In 1997, the Smilodon was selected as the logo and namesake for the Nashville Predators hockey team and the inspiration for their mascot, Gnash.[13] At the beginning of each match, the team enters the ice through the jaws of a large sabertooth cat head that descends from the ceiling. A pregame video shown on the jumbotron features a computer-generated sabertooth emerging from the ground beneath downtown Nashville.
The Hanna Barbera cartoon series "The Flintstones" featured a baby smilodon named Baby Puss as a pet for the Rubbles
In Marvel Comics, Ka-Zar, Lord of the Hidden Jungle, is found and
raised by Zabu,
the Sabertooth Tiger.
A Smilodon skeleton appeared in
a small cameo in the film Night at the
Museum: Battle of the Smithsonian.
Antinatalism is the philosophical position that asserts a negative value judgment towards birth. It has been advanced by figures such as Sophocles, Arthur Schopenhauer, Heinrich Heine, Emil Cioran, Brother Theodore[citation needed], Peter Zapffe, Philipp Mainländer and David Benatar.[1]
Sophocles wrote in his Oedipus at Colonus:
It is best not to have been born at all: but, if born, as quickly as possible to return whence one came.[2]
Heinrich Heine, who spent the last eight years of his life paralyzed, partly blind and heavily sedated on his “mattress grave” (death bed), said:
Sleep is lovely, death is better still, not to have been born is of course the miracle.
Schopenhauer, in his essay On the Suffering of the World articulates the position as follows:
If the act of procreation were neither the outcome of a desire nor accompanied by feelings of pleasure, but a matter to be decided on the basis of purely rational considerations, is it likely the human race would still exist? Would each of us not rather have felt so much pity for the coming generation as to prefer to spare it the burden of existence, or at least not wish to take it upon himself to impose that burden upon it in cold blood?[3]
Similarly, Benatar argues from the hedonistic premise that the infliction of harm is generally morally wrong and therefore to be avoided, and the intuition that the birth of a new person always entails nontrivial harm to that person, that there exists a moral imperative not to procreate.[1]
The unorthodox Biblical writer Qohelet maintains:
I further observed all the oppression that goes under the sun: the tears of the oppressed, with none to comfort them; and the power of their oppressors—with none to comfort them. Then I accounted those who died long since more fortunate than those who are still living; and happier than either are those who have not yet come into being and have never witnessed the miseries that go under the sun.[4]
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The one-child policy (simplified Chinese: 计划生育政策; pinyin: jìhuà shēngyù zhèngcè; literally "policy of birth planning") is the population control policy of the People's Republic of China (PRC). The Chinese government refers to it under the official translation of family planning policy.[1] It officially restricts the number of children married urban couples can have to one, although it allows exemptions for several cases, including rural couples, ethnic minorities, and parents without any siblings themselves.[2] A spokesperson of the Committee on the One-Child Policy has said that approximately 35.9% of China's population is currently subject to the one-child restriction.[3] The policy does not apply to the Special Administrative Regions of Hong Kong and Macau, or Tibet.
The Chinese government introduced the policy in 1979 to alleviate social, economic, and environmental problems in China,[4] and authorities claim that the policy has prevented more than 250 million births from its implementation to 2000.[2] The policy is controversial both within and outside China because of the manner in which the policy has been implemented, and because of concerns about negative economic and social consequences. The policy has been implicated in an increase in forced abortions and female infanticide, and has been suggested as a possible cause behind China's gender imbalance.[5] Nonetheless, a 2008 survey undertaken by the Pew Research Center showed that over 76% of the Chinese population supports the policy.[6]
The policy is enforced at the provincial level through fines that are imposed based on the income of the family and other factors. Population and Family Planning Commissions (Chinese: 计划 生育委员会) exist at every level of government to raise awareness about the issue and carry out registration and inspection work. Despite this policy, there are still many citizens that continue to have more than one child.[7]
China's National Population and Family Planning Commission has said that the policy will remain in place for at least another decade.[8]
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The one-child policy promotes couples having only one child in rural and urban areas. Parents with multiple births aren’t given the same benefits as parents of one child. Many times the parents have to pay money to the government in order to get permission to have another child
The limit has been strongly enforced in urban areas, but the actual implementation varies from location to location.[9] In most rural areas, families are allowed to apply to have a second child if the first is a girl,[10] or has a physical disability, mental illness or mental retardation.[11] Second children are subject to birth spacing (usually 3 or 4 years). Additional children will result in large fines: families violating the policy are required to pay monetary penalties and might be denied bonuses at their workplace. Children born in overseas countries are not counted under the policy if they do not obtain Chinese citizenship. Chinese citizens returning from abroad can have a second child.[12]
The social fostering or maintenance fee (simplified Chinese: 社会抚养费; traditional Chinese: 社會撫養費; pinyin: shèhuì fúyǎng fèi) sometimes called in the West a family planning fine, is collected as a multiple of either the annual disposable income of city dwellers or the annual cash income of peasants as determined each year by the local statistics office. The fine for a child born above the birth quota that year is thus a multiple of, depending upon the locality, either urban resident disposable income or peasant cash income estimated that year by the local statistics. So a fine for a child born ten years ago is based on the income estimate for the year of the child's birth and not of the current year.[13] They also have to pay for both the children to go to school and all the family's health care. Some children who are in one-child families pay less than the children in other families. The one child policy was designed from the outset to be a one generation policy.[14]
The one-child policy is now enforced at the provincial level, and enforcement varies; some provinces have relaxed the restrictions. Many provinces and cities, such as Henan[15] and Beijing permit two "only child" parents to have two children. As early as 1987, official policy granted local officials the flexibility to make exceptions and allow second children in the case of "practical difficulties" (such as cases in which the father is a disabled serviceman) or when both parents are single children,[16] and some provinces had other exemptions worked into their policies as well.[17] Following the 2008 Sichuan earthquake, a new exception to the regulations was announced in Sichuan province for parents who had lost children in the earthquake.[18][19] Similar exceptions have previously been made for parents of severely disabled or deceased children.[20]
Moreover, in accordance with PRC's affirmative action policies towards ethnic minorities, all non-Han ethnic groups are subjected to different rules and are usually allowed to have two children in urban areas, and three or four in rural areas. Han Chinese living in rural areas, also, are often permitted to have two children.[21] Because of couples such as these, as well as urban couples who simply pay a fine (or "social maintenance fee") to have more children,[22] the overall fertility rate of mainland China is, in fact, closer to two children per family than to one child per family (1.8). The steepest drop in fertility occurred in the 1970s before one child per family was implemented in 1979. This is due to the fact that population policies and campaigns have been ongoing in China since the 1950s. During the 1970s, a campaign of 'One is good, two is okay and three is too many' was heavily promoted.[citation needed]
In April 2007 a study by the University of California, Irvine, which claimed to be the first systematic study of the policy, found that it had proved "remarkably effective".[23] Other reports have shown population aging and negative population growth in some areas.[24]
Since the introduction of the one-child policy, the fertility rate in China has fallen from over three births per woman in 1980 (already a sharp reduction from more than five births per woman in the early 1970s) to approximately 1.8 births in 2008.[25] (The colloquial term "births per woman" is usually formalized as the Total Fertility Rate (TFR), a technical term in demographic analysis meaning the average number of children that would be born to a woman over her lifetime if she were to experience the exact current age-specific fertility rates through her lifetime.)
In total, the Chinese government estimates that it has three to four hundred million fewer people in 2008, with the one-child policy, than it would have had otherwise.[26][27] Chinese authorities thus consider the policy as a great success in helping to implement China's current economic growth. The reduction in the fertility rate and thus population growth has reduced the severity of problems that come with overpopulation, like epidemics, slums, overwhelmed social services (such as health, education, law enforcement), and strain on the ecosystem from abuse of fertile land and production of high volumes of waste. Even with the one-child policy in place, however, "China still has one million more births than deaths every five weeks."[27]
It is reported that the focus of China on population control helps provide a better health service for women and a reduction in the risks of death and injury associated with pregnancy. At family planning offices, women receive free contraception and pre-natal classes. Help is provided for pregnant women to closely monitor their health. In various places in China, the government rolled out a ‘Care for Girls’ program, which aims at eliminating cultural discrimination against girls in rural and underdeveloped areas through subsidies and education.[27]
The individual savings rate has increased since the introduction of the One Child Policy. This has been partially attributed to the policy in two respects. First, the average Chinese household expends fewer resources, both in terms of time and money, on children, which gives many Chinese more money with which to invest. Second, since young Chinese can no longer rely on children to care for them in their old age, there is an impetus to save money for the future.[28]
The original intent of the one-child policy was economic, to reduce the demand of natural resources, maintaining a steady labor rate, reducing unemployment caused from surplus labor, and reducing the rate of exploitation.[29][30] The CPC's justification for this policy was based on their support of Mao Zedong's and the Marxist theory of population growth, an idea which Marx took from Thomas Malthus.[29][30][31]
One type of criticism has come from those who acknowledge the challenges stemming from China's high population growth but believe that less intrusive options, including those that emphasized delay and spacing of births, could have achieved the same results over an extended period of time. Susan Greenhalgh's (2003) review of the policy-making process behind the adoption of the OCPF shows that some of these alternatives were known but not fully considered by China's political leaders.[32]
Another criticism is directed at the exaggerated claimed effects of the policy on the reduction in the total fertility rate. Studies by Chinese demographers, funded in part by the UN Fund for Population Activities, showed that combining poverty alleviation and health care with relaxed targets for family planning was more effective at reducing fertility than vigorous enforcement of very ambitious fertility reduction targets.[33] In 1988, Zeng Yi and professor T. Paul Schultz of Yale University discussed the effect of the transformation to the market on Chinese fertility, arguing that the introduction of the contract responsibility system in agriculture during the early 1980s weakened family planning controls during that period.[34] Zeng contended that the "big cooking pot" system of the People's Communes had insulated people from the costs of having many children. By the late 1980s, however, economic costs and incentives created by the contract system were already reducing the number of children farmers wanted.
As Hasketh, Lu, and Xing observe: "[T]he policy itself is probably only partially responsible for the reduction in the total fertility rate. The most dramatic decrease in the rate actually occurred before the policy was imposed. Between 1970 and 1979, the largely voluntary "late, long, few" policy, which called for later childbearing, greater spacing between children, and fewer children, had already resulted in a halving of the total fertility rate, from 5.9 to 2.9. After the one-child policy was introduced, there was a more gradual fall in the rate until 1995, and it has more or less stabilized at approximately 1.7 since then."[35] These researchers note further that China could have expected a continued reduction in its fertility rate just from continued economic development, had it kept to the previous policy.
The one-child policy is challenged in principle and in practice for violating human rights. Reported abuses in its enforcement include bribery, coercion, forced sterilization, forced abortion, and possibly infanticide, with most reports coming from rural areas.[36][37] A 2001 report exposed that a quota of 20,000 abortions and sterilizations was set for Huaiji County in Guangdong Province in one year due to reported disregard of the one-child policy. The effort included using portable ultrasound devices to identify abortion candidates in remote villages. Earlier reports also show that women as far along as 8.5 months pregnant were forced to abort by injection of saline solution.[38] There have also been reports of women, in their 9th month of pregnancy or already in labour, having their children killed whilst in the birth canal or immediately after birth.[39] Stephen Moore of the Cato Institute announced that the One child policy is "an ongoing genocide." He argued that free market capitalism will solve the overpopulation and overconsumption problems of developing nations.[40]
In 2002, China outlawed the use of physical force to make a woman submit to an abortion or sterilization, but it is not entirely enforced.[27][41] In the execution of the policy, many local governments still demand abortions if the pregnancy violates local regulations.
The one-child policy includes eugenic regulations. Both partners have to be rigorously tested before they marry. If one spouse has an "unsatisfactory" physical or mental condition, ranging from dyslexia to schizophrenia, they are banned from marrying. The Chinese government claimed that these regulations are intended to "improve the quality of the Chinese population." In the mid-1990s the Chinese government somewhat backed away on this policy.[42][43] According to a UNESCO debate, Chinese genetic testing is conducted with the consent of the individual and is not based on racist or sinocentric attitudes.[44]
The United Nations Population Fund (UNFPA) funding for this policy is heavily criticized in the United States.[45][46] The United States Congress pulled out of the UNFPA during the Reagan years,[40] and U.S. President George W. Bush referred to human rights abuses as his reason for stopping the US$40 million payment to the UNFPA in early 2002.[47] In early 2003 the U.S. State Department issued a press release stating that they would not continue to support the UNFPA in its present form because they believed that, at the very least, coercive birth limitation practices were not being properly addressed. The U.S. government has stated that the right to "found a family" is protected under the Universal Declaration of Human Rights.[citation needed] This, coupled with the International Conference on Population and Development's view that it is the right of the individual, not the state, to determine the number of children, represents a clear conflict between China's policy and U.S. accepted and adopted human rights conventions.[48]
As the one-child policy begins to near its next generation, one adult child is left with having to provide support for his or her two parents and four grandparents. This leaves the older generation with more of a dependency on retirement funds or charity in order to have support. If personal savings, pensions, or state welfare should fail, then the most senior citizens would be left entirely dependent upon their very small family or neighbors for support. If a child cannot care for their parents and grandparents, or if that child cannot survive, the oldest generation could find itself destitute. To combat this problem, some provinces allow families where each parent was an "only child" to have two children. In 2007 all provinces but Henan adopted this new policy.[49]
Some parents may over-indulge their only-child. The media referred to the indulged children in one-child families as "little emperors". Since the 1990s, some people have worried that this will result in a higher tendency toward poor social communication and cooperation skills among the new generation, as they have no siblings at home. However, no social studies have investigated the ratio of these over-indulged children and to what extent they are indulged. With the first generation of one-child policy children (those born in the 1980s) reaching adulthood, such worries are reduced.[50]
However, some 30 delegates called on the government in the Chinese People’s Political Consultative Conference (CPPCC) in March 2007 to abolish the one-child rule because they believe "it creates social problems and personality disorders in young people." and "It is not healthy for children to play only with their parents and be spoiled by them: it is not right to limit the number to two, either." The proposal was prepared by Ye Tingfang, a professor at the Chinese Academy of Social Sciences, who suggested that the government at least restore the previous rule that allowed couples to have up to two children. According to this scholar, "the one-child limit is too extreme. It violates nature’s law and, in the long run, will lead to mother nature’s revenge."[51][52]
Government officials and especially wealthy individuals have often been able to violate the policy in spite of fines.[53] For example, between 2000 and 2005, as many as 1,968 officials in central China's Hunan province were found to be violating the policy, according to the provincial family planning commission; also exposed by the commission were 21 national and local lawmakers, 24 political advisors, 112 entrepreneurs and 6 senior intellectuals.[54] Some of the offending officials did not face penalties,[55] although the government did respond by raising fines and calling on local officials to "expose the celebrities and high-income people who violate the family planning policy and have more than one child."[54]
China, like many other Asian countries, has a long tradition of son preference.[27] The commonly accepted explanation for son preference is that sons in rural families may be thought to be more helpful in farm work. Both rural and urban populations have economic and traditional incentives, including widespread remnants of Confucianism, to prefer sons over daughters. Sons are preferred as they provide the primary financial support for the parents in their retirement, and a son's parents typically are better cared for than his wife's. In addition, Chinese traditionally hold that daughters, on their marriage, become primarily part of the groom's family. High male-to-female sex ratios in the current population of China do not occur only in rural areas; the ratio is nearly identical in rural and urban areas.[35]
The sex ratio at birth (between male and female births) in mainland China reached 117:100 in the year 2000, substantially higher than the natural baseline, which ranges between 103:100 and 107:100. It had risen from 108:100 in 1981—at the boundary of the natural baseline—to 111:100 in 1990.[56] According to a report by the State Population and Family Planning Commission, there will be 30 million more men than women in 2020, potentially leading to social instability.[57] The correlation between the increase of sex ratio disparity on birth and the deployment of one child policy would appear to have been caused by the one-child policy.
However, other Asian regions also have higher than average ratios, including Taiwan (110:100) and South Korea (108:100), which do not have a family planning policy[58], though still lower than that of mainland China. Many studies have explored the reason for the gender-based birthrate disparity in China as well as other countries. A study in 1990 attributed the high preponderance of reported male births in mainland China to four main causes: diseases which affect females more severely than males; the result of widespread under-reporting of female births; the illegal practice of sex-selective abortion made possible by the widespread availability of ultrasound; and finally, acts of child abandonment and infanticide.[5]
In a recent paper, Emily Oster (2005) proposed a biological explanation for the gender imbalance in Asian countries, including China. Using data on viral prevalence by country as well as estimates of the effect of hepatitis on sex ratio, Oster claimed that Hepatitis B could account for up to 75% of the gender disparity in China.[59]
However, Monica Das Gupta (2005) has shown that "whether or not females 'go missing' is determined by the existing sex composition of the family into which they are conceived. Girls with no older sisters have similar chances of survival as boys. Girls conceived in families that already have a daughter, however, experience steeply higher probabilities of being aborted or of dying in early childhood. Gupta claims that cultural factors provide the overwhelming explanation for the "missing" females."[60]
The disparity in the sex ratio at birth increases dramatically after the first birth, for which the ratios remained steadily within the natural baseline over the 20 year interval between 1980 and 1999. Thus, a large majority of couples appear to accept the outcome of the first pregnancy, whether it is a boy or a girl. If the first child is a girl, however, and they are able to have a second child, then a couple may take extraordinary steps to assure that the second child is a boy. If a couple already has two or more boys, however, the sex ratio of higher parity births swings decidedly in a feminine direction.[61]
This demographic evidence indicates that while families highly value having male offspring, a secondary norm of having a girl or having some balance in the sexes of children often comes into play. For example, Zeng et al. (1993) reported a study based on the 1990 census in which they found sex ratios of just 65 or 70 boys per 100 girls for births in families that already had two or more boys.[62] A study by Anderson and Silver (1995) found a similar pattern among both Han and non-Han nationalities in Xinjiang Province: a strong preference for girls in high parity births in families that had already borne two or more boys.[63] This evidence is consistent with the observation by another researcher that for a majority of rural families "their ideal family size is one boy and one girl, at most two boys and one girl".[64]
A 2006 review article[65] by the Editorial Board of Population Research (simplified Chinese: 人口研究; pinyin: Rénkǒu Yánjiū), one of China's leading demography journals, argued that only an approach that makes the rights of women central can succeed in bringing down China's high gender ratio at birth and improve the survival rate of female infants and girls. A section written by East China Normal University demography professor Ci Qinying, "Research on the Sex Ratio at Birth Should Take a Gender Discrimination Approach," argued that researchers must pay closer attention to gender issues in demography,[66][67] and a human rights perspective in demographic research is crucial.[68][69]
The authors of another review article,
"Girl Survival in China:
History, Present Situation and Prospects," which was presented at a
2005 conference supported by the United Nations Fund for Population Activities
(UNFPA), concluded that "The Chinese government has already set the
goal of achieving a normal gender ratio at birth by 2010, and to
achieve preliminary results in establishing a new cultural outlook on
marriage and having children. The government is working to change the
system, way of thinking and other obstacles to attacking the root of
the problem. Only if equality of males and females is strongly promoted
... will the harmonious and sustainable development of society be
possible."[70]
megafaunal extinction pulses
A well-known mass extinction of megafauna, the Pleistocene–Holocene extinction, occurred at the end of the last ice age glacial period, and wiped out many giant ice age animals, such as woolly mammoths, in the Americas and northern Eurasia. However, this extinction pulse near the end of the Pleistocene was just one of a series of megafaunal extinction pulses that have occurred during the last 50,000 years over much of the Earth's surface, with Africa and southern Asia being largely spared. Outside of Eurasia, these megafaunal extinctions followed a distinctive landmass-by-landmass pattern that closely parallels the spread of humans into previously uninhabited regions of the world, and which shows no correlation with climate.[4][5] Australia was struck first around 50,000 years ago, followed by the Solomon Islands 30,000 years ago, the Americas 13,000 years ago, Cyprus 9000 years ago, the Antilles 6000 years ago, New Caledonia 3000 years ago, Madagascar 2000 years ago, New Zealand 800 years ago, the Mascarenes 400 years ago, and the Commander Islands 250 years ago. Actually, nearly all of the world's isolated islands could furnish examples of extinctions occurring shortly after the arrival of Homo sapiens. (Most of these islands, such as the Hawaiian Islands, never had terrestrial megafauna, so their extinct fauna were smaller.)
Continuing human hunting and environmental disturbance has led to additional megafaunal extinctions in the recent past, and has created a serious danger of further extinctions in the near future (see examples below).
A number of other mass extinctions occurred earlier in Earth's geologic history, in which some or all of the megafauna of the time also died out. Famously, in the Cretaceous–Tertiary extinction event the dinosaurs and most other giant reptilians were eliminated. However, the earlier mass extinctions were more global and not so selective for megafauna; i.e., many species of other types, including plants, marine invertebrates and plankton, went extinct along with the dinosaurs. Thus, the earlier events must have been caused by more generalized types of disturbances to the biosphere.
The Quaternary period saw the extinctions of numerous predominantly larger species, many of which occurred during the transition to the Holocene epoch in what is termed the Holocene extinction[citation needed]. Among the main causes hypothesized by paleontologists are natural climate change and overkill by humans, who appeared during this epoch. A variant of this last possibility is the second-order predation hypothesis, which focuses more on the indirect damage caused by overcompetition with nonhuman predators. The spread of disease is also discussed as a possible reason.
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The Ice Age extinction event saw the extinction of many mammals weighing more than 40 kg. In North America around 33 of 45 genera of large mammals became extinct, in South America 46 of 58, in Australia 15 of 16, in Europe 7 of 23, but in Subsaharan Africa only 2 of 44. The extinctions in the Americas entailed the elimination of all the larger (over 100 kg) mammalian species of South American origin, including those that had migrated north in the Great American Interchange. Only in North America, South America and Australia did the extinction occur at family taxonomic levels or higher.
There are two main hypotheses concerning the Pleistocene extinction:
There are some inconsistencies between the current available data and the prehistoric overkill hypothesis. For instance, there are ambiguities around the timing of sudden extinctions of Australian megafauna. Biologists note that comparable extinctions have not occurred in Africa and South or Southeast Asia, where the fauna evolved with hominids. Post-glacial megafaunal extinctions in Africa have been spaced over a longer interval.
Evidence supporting the prehistoric overkill hypothesis includes the persistence of certain island megafauna for several millennia past the disappearance of their continental cousins. Ground sloths survived on the Antilles long after North and South American ground sloths were extinct. The later disappearance of the island species correlates with the later colonization of these islands by humans. Similarly, woolly mammoths died out on remote Wrangel Island 7000 years after their mainland extinction. Steller's sea cows also persisted off the isolated and uninhabited Commander Islands for thousands of years after they vanished from continental shores of the north Pacific.[1]
Controversial alternative hypotheses to the theory of human responsibility include the Younger Dryas event and Tollmann's hypothetical bolide, which claim that the extinctions resulted from bolide impact(s). However, such hypotheses would predict an instantaneous, regional extinction(s), and thus cannot account for the planet-wide species losses that occurred over an interval of thousands of years.
(40,000-10,000 years ago)
(by 9000 years ago)
During the last 50,000 years, including the end of the last glacial period, approximately 33 genera of large mammals have become extinct in North America. Of these, 15 genera extinctions can be reliably attributed to a brief interval of 11,500 to 10,000 radiocarbon years before present, shortly following the arrival of the Clovis people in North America. Most other extinctions are poorly constrained in time, though some definitely occurred outside of this narrow interval.[3] Contrary to this, only about half a dozen small mammals disappeared during this time. Previous North American extinction pulses had occurred at the end of glaciations, but not with such an imbalance between large mammals and small ones. (Moreover, previous extinction pulses were not comparable to the Quaternary extinction event; they involved primarily species replacements within ecological niches, while the latter event resulted in many ecological niches being left unoccupied.) The megafaunal extinctions include twelve genera of edible herbivores (H), and five large, dangerous carnivores (C). North American extinctions included:
The survivors are in some ways as significant as the losses: bison, moose (a latest Pleistocene immigrant through Beringia), elk, caribou, deer, pronghorn, muskox, bighorn sheep, and mountain goat. All save the pronghorns descended from Asian ancestors that had evolved with human predators.[4] Pronghorns are the second fastest land mammal (after the cheetah), which may have helped them elude hunters. More difficult to explain in the context of overkill is the survival of bison, since these animals first appeared in North America less than 240,000 years ago [5][6][7]and so were geographically removed from human predators for a sizeable period of time. Because ancient bison evolved into living bison[8][9], there was no continent-wide extinction of bison at the end of the Pleistocene (although the genus was regionally extirpated in many areas). The survival of Bison into the Holocene and recent times is therefore difficult to explain via overkill, since these animals -- separated from human hunters by more than 200,000 years -- would almost certainly have been very nearly as naive as native North American large mammals.
The culture that has been connected with the wave of extinctions in North America is the paleo-Indian culture associated with the Clovis people (q.v.), who were thought to use spear throwers to kill large animals. The chief opposition to the "prehistoric overkill hypothesis" has been that population of humans such as the Clovis culture was too small to be ecologically significant. Other generalized evocations of climate change fail under detailed scrutiny.
Lack of tameable megafauna was perhaps one of the reasons why Amerindian civilizations evolved differently than Old World ones.[10] Critics have disputed this by arguing that llamas, alpacas, and bison were domesticated.[11]
At the Pleistocene-Holocene transition South America, which had remained largely unglaciated except for increased mountain glaciation in the Andes, saw an extinction wave, which carried off many large species. Today there is no wild land mammal left on this continent weighing more than a tapir.
The sudden spate of extinctions occurred earlier than in the Americas. Most evidence points to the period immediately after the first arrival of humans — thought to be a little under 50,000 years ago — but scientific argument continues as to the exact date range. The Australian extinctions included:
Some extinct megafauna, such as the bunyip-like Diprotodon, may be the sources of ancient cryptozoological legends.
c. AD 1500, several species became extinct after Polynesian settlers arrived, including:
Recent research, based on archaeological and paleontological digs on 70 different islands, has shown that numerous species went extinct as people moved across the Pacific, starting 30,000 years ago in the Bismarck Archipelago and Solomon Islands (Steadman & Martin 2003). It is currently estimated that among the bird species of the Pacific some 2000 species have gone extinct since the arrival of humans (Steadman 1995). Among the extinctions were:
Starting with the arrival of humans c. 2000 years ago, nearly all of the island's megafauna became extinct, including:
Though the effect wasn't devastating, certain large African mammals died from the continent.
Starting c. 500 years ago, a number of species became extinct upon human settlement of the islands, including:
The hunting hypothesis suggests that humans hunted megaherbivores to extinction. As a result, carnivores and scavengers that depended upon those animals became extinct from lack of prey.[12][13][14] Therefore this hypothesis holds Pleistocene humans responsible for the megafaunal extinction. One variant, often referred to as blitzkrieg, portrays humans as hunting the megafauna to extinction within a relatively short period of time. Some of the direct evidence for this includes: fossils of some megafauna found in conjunction with human remains, embedded arrows and tool cut marks found in megafaunal bones, and European cave paintings that depict such hunting. Biogeographical evidence is also suggestive; the areas of the world where humans evolved currently have more of their Pleistocene megafaunal diversity (the elephants and rhinos of Asia and Africa) compared to other areas such as Australia, the Americas, Madagascar and New Zealand, areas where early humans were non-existent. In addition, where animals have not been hunted for several years they become naive. Based on this evidence, a picture arises of the megafauna of Asia and Africa evolving with humans, learning to be wary of them, and in other parts of the world the wildlife appearing ecologically naive and easier to hunt. This is particularly true of island fauna, which display a dangerous lack of fear of humans. Of course, it is impossible to demonstrate that continental mammals were possessed of a similar naïveté.
Circumstantially, the close correlation in time between the appearance of humans in an area and extinction there provides weight for this scenario. This is perhaps the strongest evidence, as it is almost impossible that it could be coincidental when science has so many data points. For example, the woolly mammoth survived on islands despite changing climatic conditions for thousands of years after the end of the last glaciation, but they died out when humans arrived around 1700 BC. The megafaunal extinctions covered a vast period of time and highly variable climatic situations. The earliest extinctions in Australia were complete approximately 30,000 BP, well before the last glacial maximum and before rises in temperature. The most recent extinction in New Zealand was complete no earlier than 500 BP and during a period of cooling. In between these extremes megafaunal extinctions have occurred progressively in such places as North America, South America and Madagascar with no climatic commonality. The only common factor that can be ascertained is the arrival of humans.[15][16]
World wide extinctions seem to follow the migration of humans and to be most severe where humans arrived most recently and least severe where humans were originally – Africa (see figure at left). This suggests that in Africa, where humans evolved, prey animals and human hunting ability evolved together, so the animals evolved avoidance techniques. As humans migrated throughout the world and became more and more proficient at hunting, they encountered animals that had evolved without the presence of humans. Lacking the fear of humans that African animals had developed, animals outside of Africa were easy prey for human hunting techniques. It also suggests that this is independent of climate change (see figure at left).
Extinction through human hunting has been supported by archaeological finds of mammoths with projectile points embedded in their skeletons, by observations of modern naïve animals allowing hunters to approach easily [17][18][19] and by computer models by Mosimann and Martin,[20] and Whittington and Dyke,[21] and most recently by Alroy.[22]
The overkill hypothesis, a variant of the hunting hypothesis, was proposed 40 years ago by Paul S. Martin, now Professor of Geosciences Emeritus at the Desert Laboratory of the University of Arizona. It sparked debate which continues today. It explains why the megafaunal extinctions occurred within a relatively short period of time. The most convincing evidence of his theory is that 80% of the North American large mammal species disappeared within 1000 years of the arrival of humans in the Americas.
The major objections to the theory are as follows:
At the end of the 19th and beginning of the 20th centuries, when scientists first realized that there had been glacial and interglacial ages, and that they were somehow associated with the prevalence or disappearance of certain animals, they surmised that the termination of the Pleistocene ice age might be an explanation for the extinctions.
Critics object that since there were multiple glacial advances and withdrawals in the evolutionary history of many of the megafauna, it is rather implausible that only after the last glacial would there be such extinctions. However, this criticism is rejected by a recent study indicating that terminal Pleistocene megafaunal community composition may have differed markedly from faunas present during earlier interglacials, particularly with respect to the great abundance and geographic extent of Pleistocene Bison at the end of the epoch[31]. This suggests that the survival of megafaunal populations during earlier interglacials is essentially irrelevant to the terminal Pleistocene extinction event, because bison were not present in similar abundance during any of the earlier interglacials.
Some evidence weighs against climate change as a valid hypothesis as applied to Australia. It has been shown that the prevailing climate at the time of extinction (40,000–50,000 BP) was similar to that of today, and that the extinct animals were strongly adapted to an arid climate. The evidence indicates that all of the extinctions took place in the same short time period, which was the time when humans entered the landscape. The main mechanism for extinction was likely fire (started by humans) in a then much less fire-adapted landscape. Isotopic evidence shows sudden changes in the diet of surviving species, which could correspond to the stress they experienced before extinction.[32][33][34]
The most obvious change associated with the termination of an ice age is the increase in temperature. Between 15,000 BP and 10,000 BP, a 6°C increase in global mean annual temperatures occurred. This was generally thought to be the cause of the extinctions.
According to this hypothesis, a temperature increase sufficient to melt the Wisconsin ice sheet could have placed enough thermal stress on cold-adapted mammals to cause them to die. Their heavy fur, which helps conserve body heat in the glacial cold, might have prevented the dumping of excess heat, causing the mammals to die of heat exhaustion. Large mammals, with their reduced surface area-to-volume ratio, would have fared worse than small mammals.
More recent research has demonstrated that the annual mean temperature of the current interglacial that we have seen for the last 10,000 years is no higher than that of previous interglacials, yet some of the same large mammals survived similar temperature increases. Therefore warmer temperatures alone may not be a sufficient explanation[35][36][37][38][39][40]. However, a recent study has demonstrated that Pleistocene bison were more abundant and more widely distributed in North America at the end of the Pleistocene than at any previous time during the epoch, and in many continental regions was among the most common large herbivores[31]. The documented increase in abundance of bison in midcontinent North America preceded the extinction event, and so cannot have been a result of the extinction[31]. Although it is premature to suggest that the increasing abundance of bison may have driven the extinction, these data nevertheless demonstrate that terminal Pleistocene megafaunal community composition was significantly different during the end-Pleistocene warming phase than that from any earlier warming periods.
In addition, numerous species such as mammoths on Wrangel Island[41] and St. Paul Island survived in human-free refugia despite changes in climate. This is precisely the opposite of what would be expected if climate change were responsible. Under normal ecological assumptions island populations should be more vulnerable to extinction due to climate change because of small populations and an inability to migrate to more favorable climes.
Other scientists have proposed that increasingly extreme weather — hotter summers and colder winters — referred to as "continentality", or related changes in rainfall caused the extinctions. The various hypotheses are outlined below.
It has been shown that vegetation changed from mixed woodland-parkland to separate prairie and woodland.[38][40][37] This may have affected the kinds of food available. If so, herbivores might not have found the plants with which they had evolved and thus would have fallen prey to the anti-herbivory toxins in the plants that remained available. Shorter growing seasons may have caused the extinction of large herbivores and the dwarfing of many others. In this case, as observed, bison and other large ruminants would have fared better than horses, elephants and other monogastrics, because ruminants are able to extract more nutrition from limited quantities of high-fiber food and better able to deal with anti-herbivory toxins.[42][43][44] So, in general, when vegetation becomes more specialized, herbivores with less diet flexibility may be less able to find the mix of vegetation they need to sustain life and reproduce, within a given area.
Increased continentality resulted in reduced and less predictable rainfall limiting the availability of plants necessary for energy and nutrition.[45][46][47] Axelrod[48] and Slaughter[49] have suggested that this change in rainfall restricted the amount of time favorable for reproduction. This could disproportionately harm large animals, since they have longer, more inflexible mating periods, and so may have produced young at unfavorable seasons (i.e., when sufficient food, water, or shelter was unavailable because of shifts in the growing season. In contrast, small mammals, with their shorter life cycles, shorter reproductive cycles, and shorter gestation periods, could have adjusted to the increased unpredictability of the climate, both as individuals and as species which allowed them to synchronize their reproductive efforts with conditions favorable for offspring survival. If so, smaller mammals would have lost fewer offspring and would have been better able to repeat the reproductive effort when circumstances once more favored offspring survival.[50]
Critics have identified a number of problems with the continentality hypotheses.
The extinction of the megafauna could have caused the disappearance of the mammoth steppe. Alaska now has low nutrient soil unable to support bison, mammoths, and horses. R. Dale Guthrie has claimed this as a cause of the extinction of the megafauna there; however, he may be Interpreting it backwards. The loss of large herbivores to break up the permafrost allows the cold soils that are unable to support large herbivores today. Today, in the arctic, where trucks have broken the permafrost broken grasses and diverse flora and fauna can be supported. [61][62] In addition, Chapin (Chapin 1980) showed that simply adding fertilizer to the soil in Alaska could make grasses grow again like they did in the era of the mammoth steppe. Possibly, the extinction of the megafauna and the corresponding loss of dung is what led to low nutrient levels in modern day soil and therefore is why the landscape can no longer support megafauna.
Detractors have asserted that neither the Overkill sensu stricto nor Climate Change hypotheses explain several observations.
Because of perceived shortcomings of the Overkill or Climate Change hypotheses alone, some scientists support a combination of Climate Change and Overkill.
The Hyperdisease Hypothesis attributes the extinction of large mammals during the late Pleistocene to indirect effects of the newly arrived aboriginal humans.[63][64][65] The Hyperdisease Hypothesis proposes that humans or animals traveling with them (e.g., chickens or domestic dogs) introduced one or more highly virulent diseases into vulnerable populations of native mammals, eventually causing extinctions. The extinction was biased toward larger-sized species because smaller species have greater resilience because of their life history traits (e.g., shorter gestation time, greater population sizes, etc). Humans are thought to be the cause because other earlier immigrations of mammals into North America from Eurasia did not cause extinctions.[63]
Diseases imported by people have been responsible for extinctions in the recent past; for example, bringing avian malaria to Hawaii has had a major impact on the isolated birds of the island.
If a disease was indeed responsible for the end-Pleistocene extinctions, then there are several criteria it must satisfy (see Table 7.3 in MacPhee & Marx 1997). First, the pathogen must have a stable carrier state in a reservoir species. That is, it must be able to sustain itself in the environment when there are no susceptible hosts available to infect. Second, the pathogen must have a high infection rate, such that it is able to infect virtually all individuals of all ages and sexes encountered. Third, it must be extremely lethal, with a mortality rate of c. 50–75%. Finally, it must have the ability to infect multiple host species without posing a serious threat to humans. Humans may be infected, but the disease must not be highly lethal or able to cause an epidemic.
One suggestion is that pathogens were transmitted by the expanding humans via the domesticated dogs they brought with them.[66] Unfortunately for such a theory it can not account for several major extinction events, notably Australia and North America. Dogs did not arrive in Australia until approximately 35,000 years after the first humans arrived and approximately 30,000 years after the megafaunal extinction was complete and as such can not be implicated. In contrast numerous species including wolves, mammoths, camelids and horses had emigrated continually between Asia and North America over the past 100,000 years. For the disease hypothesis to be applicable in the case of the Americas it would require that the population remain immunologically naive despite this constant transmission of genetic and pathogenic material.
The Second-Order Predation Hypothesis says that as humans entered the New World they continued their policy of killing predators, which upset the ecological balance of the continent causing overpopulation, environmental exhaustion, and environmental collapse. The hypothesis accounts for changes in animal, plant, and, human populations.
The scenario is as follows:
This has been supported by a computer model, the Pleistocene Extinction Model (PEM), which, using the same assumptions and values for all variables (herbivore population, herbivore recruitment rates, food needed per human, herbivore hunting rates, etc) other than those for hunting of predators. It compares the Overkill hypothesis (predator hunting = 0) with Second-Order Predation (predator hunting varied between 0.01 and 0.05 for different runs) . The findings are that Second Order-Predation is more consistent with extinction than is Overkill[68][69] (results graph at left).
The PEM is the only test of multiple hypotheses and is the only model to specifically test combination hypotheses by artificially introducing sufficient climate change to cause extinction. When Overkill and Climate Change are combined they balance each other out. Climate Change reduces the number of plants, Overkill removes animals, therefore fewer plants are eaten. Second-Order Predation combined with Climate Change exacerbates the effect of Climate Change. [70] (results graph at right).
The second-order predation hypothesis is supported by the observation above that there was a massive increase in bison populations.(Scott)[71]
First publicly presented at the Spring
2007 joint assembly of the American Geophysical Union in
Acapulco, Mexico, the comet hypothesis
suggests that the mass extinction was caused by a swarm of comets
12,900 years ago. Debate around this hypothesis has included, among
other things, the lack of an impact crater, relatively small increased
level of iridium
in the soil, and the highly improbable nature of such an event. Using photomicrograph
analysis, research published in January 2009 has found evidence of nanodiamonds
in the soil from six sites across North America including Arizona,
Minnesota, Oklahoma, South Carolina and two Canadian sites. Similar
research found nanodiamonds in the Greenland ice sheet.[73][74][75]
| Woolly
Rhinoceros Fossil range: Late Pleistocene |
|
|---|---|
 |
|
| Woolly rhinoceros (Coelodonta antiquitatis), skeleton on display | |
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Perissodactyla |
| Family: | Rhinocerotidae |
| Genus: | Coelodonta Bronn, 1831 |
| Species: | C. antiquitatis |
| Binomial name | |
| Coelodonta antiquitatis (Blumenbach, 1807) |
|
The woolly rhinoceros (Coelodonta antiquitatis) is an extinct species of rhinoceros native to the northern steppes of Eurasia that lived during the Pleistocene epoch and survived the last glacial period. The woolly rhinoceros are members of the Pleistocene megafauna.
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An adult woolly rhinoceros was 3.7 on metres (12 feet) in length on average, but they could probably grow to 4.3 - 4.4 meters at the largest. This is more than the modern white rhino. The Woolly rhinoceros could grow up to be 3.3 meters tall. Two horns on the skull were made of keratin, the anterior horn being 1 metre (3 feet) in length, with a smaller horn between its eyes. It had thick, long fur, small ears, short, thick legs, and a stocky body. Cave paintings suggest a wide dark band between the front and hind legs, but it is not universal and identification of rhinoceros as woolly rhinoceros is uncertain. The woolly rhinoceros used its horns to sweep snow away from vegetation so it could eat in the winter[citation needed], and is also thought to have used its horns for defensive purposes and to attract mates.
As the last and most derived member of the Pleistocene rhinoceros lineage, the woolly rhinoceros was supremely well adapted to its environment. Stocky limbs and thick woolly pelage made it well suited to the steppe-tundra environment prevalent across the Palearctic ecozone during the Pleistocene glaciations. Its geographical range expanded and contracted with the alternating cold and warm cycles, forcing populations to migrate as glaciers receded. Like the vast majority of rhinoceroses, the body plan of the woolly rhinoceros adhered to the conservative morphology, like the first rhinoceroses seen in the late Eocene. A close relative, the Elasmotherium had a more southern range.
Controversy has long surrounded the precise dietary preference of Coelodonta as past investigations have found both grazing and browsing modes of life to be plausible. The palaeodiet of the woolly rhinoceros has been reconstructed using several lines of evidence. Climatic reconstructions indicate the preferred environment to have been cold and arid steppe-tundra, with large herbivores forming an important part of the feedback cycle. Pollen analysis shows a prevalence of grasses and sedges within a more complicated vegetation mosaic.[citation needed]
A strain vector biomechanical investigation of the skull, mandible and teeth of a well-preserved last cold stage individual recovered from Whitemoor Haye, Staffordshire, revealed musculature and dental characteristics that support a grazing feeding preference. In particular, the enlargement of the temporalis and neck muscles is consistent with that required to resist the large tugging forces generated when taking large mouthfuls of fodder from the ground. The presence of a large diastema supports this theory.
Comparisons with extant perissodactyls confirm that Coelodonta was a hindgut fermentor with a single stomach, and as such would have grazed upon cellulose-rich, protein-poor fodder. This method of digestion would have required a large throughput of food and thus links the large mouthful size to the low nutritive content of the chosen grasses and sedges.[1]
Many species of Pleistocene megafauna, like the woolly rhinoceros, became extinct around the same time period. Human and Neanderthal hunting is often cited as one cause.[2] Other theories for the cause of the extinctions are climate change associated with the receding Ice age and the hyperdisease hypothesis.[3]
Its shape was known only from prehistoric cave drawings until a completely preserved specimen (missing only the fur and hooves) was discovered in a tar pit in Starunia, Poland. The specimen, an adult female, is now on display in the Polish Academy of Sciences' Museum of Natural History in Kraków. The woolly rhinoceros roamed much of Northern Europe and was common in the then cold, arid desert that is southern England and the North Sea today. During Greenland Stadial 2 (the Last Glacial Maximum) the North Sea did not exist as sea levels were up to 125 metres (410 ft) lower than today.
The woolly rhinoceros co-existed with woolly mammoths and several other extinct larger mammals. No specimens have been dated in the U.K. after 15,000 14C years B.P.[citation needed]
Recent radiocarbon dating indicates that populations survived as recently as 8,000 B.C. in Western Siberia. However, the accuracy of this date is uncertain as several radiocarbon plateaus exist around this time. The extinction does not coincide with the end of the last ice age but does coincide however, with a minor yet severe climatic reversal that lasted for about 1,000–1,250 years, the Younger Dryas (GS1 - Greenland Stadial 1), characterized by glacial readvances and severe cooling globally, a brief interlude in the continuing warming subsequent to the termination of the last major ice age (GS2), thought to have been due to a shutdown of the thermohaline circulation in the ocean due to huge influxes of cold, fresh water from the preceding sustained glacial melting during the warmer Interstadial (GI1 - Greenland Interstadial 1 - ca. 16,000 - 11,450 14C years B.P.).
A relative, the hairy sumatran rhinoceros
(Dicerorhinus sumatrensis), still lives in Southeast Asia, as an endangered species.
| Camelops Fossil range: late Pliocene to late Pleistocene |
|
|---|---|
 |
|
| Camelops hesternus in the George C. Page Museum, Los Angeles | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Family: | Camelidae |
| Tribe: | †Camelopini |
| Genus: | †Camelops |
| Species | |
|
†Camelops
sulcatus |
|
Camelops is an extinct genus of camels that once roamed western North America, where it disappeared at the end of the Pleistocene about 10,000 years ago. Its name is derived from the Greek κάμελος (camel) + ὀψ (face), thus "camel-face."
Camelops first appeared during the Late Pliocene period and became extinct at the end of the Pleistocene. Its extinction was part of a larger North American die-off in which native horses, camelids and mastodons also died out. This megafaunal extinction coincided roughly with the appearance of the big game hunting Clovis culture, and biochemical analyses have shown that Clovis tools were used in butchering camels.[1]
Because soft tissues are generally not preserved in the fossil record, it is not certain if Camelops possessed a hump, like modern camels, or lacked one, like its modern llama relatives.
Camelops hesternus was seven feet (slightly over two meters) at the shoulder, making it slightly taller than modern Bactrian camels. Plant remains found in its teeth exhibit little grass, suggesting that the camel was an opportunistic herbivore; that is, it ate any plants that were available, as do modern camels.
The Wal-Mart camel is the bone fossil of a prehistoric camel (Camelops sp.) found at a future Wal-Mart store in Mesa, Arizona in 2007. Workers digging a hole for an ornamental citrus tree found the bones of a camel that lived 10,000 years ago. Arizona State University geology museum curator Brad Archer calls it an important find and extremely rare.[2] Wal-Mart officials and Greenfield Citrus Nursery owner John Babiarz agreed that the bones will go directly on display in a museum at Arizona State University. Camels lived in what is now Arizona until about 8,000 years ago.[3] More camel bones were found in Gilbert, Arizona in May 2008.[4][5]
| Mastodon Fossil range: 34–0 Ma |
|
|---|---|
 |
|
| Mounted mastodon skeleton, Museum of the Earth . | |
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Proboscidea |
| Family: | †Mammutidae Hay, 1922 |
| Genus: | †Mammut Blumenbach, 1799 |
| Species | |
Mastodons or mastodonts (Greek: μαστός "breast" and οδούς, "tooth") were large tusked mammal species of the extinct genus Mammut found in Asia, Africa, Europe, North America and Central America.[1] The American mastodon is the most recent and best known species of the group. Confusingly, several genera of proboscids from the gomphothere family have similar-sounding names (e.g., Stegomastodon) but are actually more closely related to elephants than to mastodons.
The genus gives its name to the family Mammutidae, assigned to the order Proboscidea. They superficially resemble members of the proboscidean family Elephantidae, including mammoths; however, mastodons were browsers while mammoths were grazers.
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Mastodons first appeared almost 40 million years ago; the oldest fossil (Mastodon sp.) was unearthed in the Democratic Republic of the Congo. Fossils have also been found in Bolivia, England, Germany, the Netherlands, North America, and Romania[2] and northern Greece. The Mastodon was thought to be partly aquatic[by whom?].
While mastodons had a size and appearance similar to elephants and mammoths, they were not particularly closely related. Their teeth differ dramatically from those of members of the elephant family; they had blunt, conical, nipple-like projections on the crowns of their molars,[3] which were more suited to chewing leaves than the high-crowned teeth mammoths used for grazing; the name mastodon (or mastodont) means "nipple teeth" and is also an obsolete name for their genus.[4] Their skulls are larger and flatter than those of mammoths, while their skeleton is stockier and more robust.[5]
The American mastodon (Mammut americanum), the most recent member of the family, lived from about 3.7 million years ago until it became extinct about 10,000 years BCE It is known from fossils found ranging from present-day Alaska and New England in the north, to Florida, southern California, and as far south as Honduras.[6] The American mastodon resembled a woolly mammoth in appearance, with a thick coat of shaggy hair.[7] It had tusks that sometimes exceeded five meters in length; they curved upwards, but less dramatically than those of the woolly mammoth.[5] Its main habitat was cold spruce woodlands, and it is believed to have browsed in herds.[8] They are generally reported as having disappeared from North America about 10,000 years ago,[9] as part of a mass extinction of most of the Pleistocene megafauna. Paleo-Indians entered the American continent in relatively large numbers 13,000 years ago,[10] and their hunting may have caused a gradual attrition of the mastodon population.[11]
Mammut cosoensis was endemic to North America, from the Pliocene, living from 4.9—1.8 mya, existing for approximately .[12] Pliomastodon cosoensis was named by Schultz (1937). Its first fossil location is the Coso Mountains in California. It was recombined as Mammut cosoensis by Shoshani and Tassy (1996).[13][14]
Mammut furlongi was endemic only to North America and from the Miocene living from 23.03—5.33 mya, existing for approximately .[15] Mammut furlongi was named by Shotwell and Russell (1963). Its first fossil location is Black Butte, a Miocene terrestrial horizon in the Juntura Formation of Oregon.[16]
Mammut raki was endemic to North America from the Pliocene, living from 4.9—1.8 mya, existing for approximately .[17] Mastodon raki was named by Frick (1933). Its type locality is Elephant Butte Reservoir, New Mexico. It was recombined as Mammut raki by Tedford (1981) and Lucas and Morgan (1999).[18][19]
Mammut spenceri was endemic to North America from the Miocene, living from 16.9—16 mya, existing for approximately .[20]
Mastodon spenceri was named by Fourtau (1918). Its type locality is Wadi Moghra, Egypt.[21]
Excavations conducted from 1993 through early 2000 at the Diamond Valley Lake reservoir outside of Hemet in Riverside County, California yielded numerous remains of mastodon, as well as numerous other Pleistocene animals. The abundance of these remains, all recovered by paleontologists from the San Bernardino County Museum, led to the site being nicknamed the "Valley of the Mastodons".
Current excavations are going on annually at the Hiscock Site in Byron, New York, for mastodon and related paleo-Indian artifacts. The site was discovered in 1959 by the Hiscock family while digging a pond with a backhoe; they found a large tusk and stopped digging. The Buffalo Museum of Science has organized the dig since 1983. There were also excavations at Montgomery, New York in the late 1990s.
In July 2007, a team of Greek and Dutch paleontologists, excavated the longest mastodon tusks in the world in Milia, a village near Grevena. The tusks each measure 5 meters long, and weigh 1 ton. Experts believe that the mammal was a 25-30 years old male, 3.5 meters tall and weighed approximately 6 tons.[22][23]
In August 2008, miners in Romania unearthed the skeleton of a 2.5 million-year-old mastodon, believed to be one of the best preserved in Europe.[24] Ninety percent of the skeleton's bones were intact, with damage to the skull and tusks.[24] In 2009 a family in Portland, Michigan unearthed mastodon bones while excavating a new pond on their property. It is one of approximately 250 mastodons found in Michigan over the past century.[25]
As of July 2009, six mastodon fossils were discovered in Elmacık village of Kemer town of south-western province of Burdur, Turkey in the past four years. Also the first excavation to discover mastodon fossils took place in Elmacik village in 2006.[26]
In August 2009 workers in Indiana digging a coal slurry storage pit unearthed mastodon remains. These remains include pieces of ribs, skull, tusks, and a kneecap. Remains have been turned over to the Indiana State Museum for study and preservation.[27]
| Mastodon Fossil range: 34–0 Ma |
|
|---|---|
|
|
| Mounted mastodon skeleton, Museum of the Earth . | |
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Proboscidea |
| Family: | †Mammutidae Hay, 1922 |
| Genus: | †Mammut Blumenbach, 1799 |
| Species | |
Mastodons or mastodonts (Greek: μαστός "breast" and οδούς, "tooth") were large tusked mammal species of the extinct genus Mammut found in Asia, Africa, Europe, North America and Central America.[1] The American mastodon is the most recent and best known species of the group. Confusingly, several genera of proboscids from the gomphothere family have similar-sounding names (e.g., Stegomastodon) but are actually more closely related to elephants than to mastodons.
The genus gives its name to the family Mammutidae, assigned to the order Proboscidea. They superficially resemble members of the proboscidean family Elephantidae, including mammoths; however, mastodons were browsers while mammoths were grazers.
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Mastodons first appeared almost 40 million years ago; the oldest fossil (Mastodon sp.) was unearthed in the Democratic Republic of the Congo. Fossils have also been found in Bolivia, England, Germany, the Netherlands, North America, and Romania[2] and northern Greece. The Mastodon was thought to be partly aquatic[by whom?].
While mastodons had a size and appearance similar to elephants and mammoths, they were not particularly closely related. Their teeth differ dramatically from those of members of the elephant family; they had blunt, conical, nipple-like projections on the crowns of their molars,[3] which were more suited to chewing leaves than the high-crowned teeth mammoths used for grazing; the name mastodon (or mastodont) means "nipple teeth" and is also an obsolete name for their genus.[4] Their skulls are larger and flatter than those of mammoths, while their skeleton is stockier and more robust.[5]
The American mastodon (Mammut americanum), the most recent member of the family, lived from about 3.7 million years ago until it became extinct about 10,000 years BCE It is known from fossils found ranging from present-day Alaska and New England in the north, to Florida, southern California, and as far south as Honduras.[6] The American mastodon resembled a woolly mammoth in appearance, with a thick coat of shaggy hair.[7] It had tusks that sometimes exceeded five meters in length; they curved upwards, but less dramatically than those of the woolly mammoth.[5] Its main habitat was cold spruce woodlands, and it is believed to have browsed in herds.[8] They are generally reported as having disappeared from North America about 10,000 years ago,[9] as part of a mass extinction of most of the Pleistocene megafauna. Paleo-Indians entered the American continent in relatively large numbers 13,000 years ago,[10] and their hunting may have caused a gradual attrition of the mastodon population.[11]
Mammut cosoensis was endemic to North America, from the Pliocene, living from 4.9—1.8 mya, existing for approximately .[12] Pliomastodon cosoensis was named by Schultz (1937). Its first fossil location is the Coso Mountains in California. It was recombined as Mammut cosoensis by Shoshani and Tassy (1996).[13][14]
Mammut furlongi was endemic only to North America and from the Miocene living from 23.03—5.33 mya, existing for approximately .[15] Mammut furlongi was named by Shotwell and Russell (1963). Its first fossil location is Black Butte, a Miocene terrestrial horizon in the Juntura Formation of Oregon.[16]
Mammut raki was endemic to North America from the Pliocene, living from 4.9—1.8 mya, existing for approximately .[17] Mastodon raki was named by Frick (1933). Its type locality is Elephant Butte Reservoir, New Mexico. It was recombined as Mammut raki by Tedford (1981) and Lucas and Morgan (1999).[18][19]
Mammut spenceri was endemic to North America from the Miocene, living from 16.9—16 mya, existing for approximately .[20]
Mastodon spenceri was named by Fourtau (1918). Its type locality is Wadi Moghra, Egypt.[21]
Excavations conducted from 1993 through early 2000 at the Diamond Valley Lake reservoir outside of Hemet in Riverside County, California yielded numerous remains of mastodon, as well as numerous other Pleistocene animals. The abundance of these remains, all recovered by paleontologists from the San Bernardino County Museum, led to the site being nicknamed the "Valley of the Mastodons".
Current excavations are going on annually at the Hiscock Site in Byron, New York, for mastodon and related paleo-Indian artifacts. The site was discovered in 1959 by the Hiscock family while digging a pond with a backhoe; they found a large tusk and stopped digging. The Buffalo Museum of Science has organized the dig since 1983. There were also excavations at Montgomery, New York in the late 1990s.
In July 2007, a team of Greek and Dutch paleontologists, excavated the longest mastodon tusks in the world in Milia, a village near Grevena. The tusks each measure 5 meters long, and weigh 1 ton. Experts believe that the mammal was a 25-30 years old male, 3.5 meters tall and weighed approximately 6 tons.[22][23]
In August 2008, miners in Romania unearthed the skeleton of a 2.5 million-year-old mastodon, believed to be one of the best preserved in Europe.[24] Ninety percent of the skeleton's bones were intact, with damage to the skull and tusks.[24] In 2009 a family in Portland, Michigan unearthed mastodon bones while excavating a new pond on their property. It is one of approximately 250 mastodons found in Michigan over the past century.[25]
As of July 2009, six mastodon fossils were discovered in Elmacık village of Kemer town of south-western province of Burdur, Turkey in the past four years. Also the first excavation to discover mastodon fossils took place in Elmacik village in 2006.[26]
In August 2009 workers in Indiana digging a coal slurry storage pit unearthed mastodon remains. These remains include pieces of ribs, skull, tusks, and a kneecap. Remains have been turned over to the Indiana State Museum for study and preservation.[27]
