Short description: Extinction event occurring during the late Quaternary period
Late Pleistocene landscape of northern Spain , by Mauricio Antón (left to right: Equus ferus, Mammuthus primigenius, Rangifer tarandus, Panthera spelaea, Coelodonta antiquitatis)
The latter half of the Late Pleistocene to the beginning of the Holocene (~50,000-10,000 years Before Present)[1] saw extinctions of numerous predominantly megafaunal species, which resulted in a collapse in faunal density and diversity across the globe. The extinctions during the Late Pleistocene are differentiated from previous extinctions by the widespread absence of ecological succession to replace these extinct megafaunal species,[2] and the regime shift of previously established faunal relationships and habitats as a consequence. The timing and severity of the extinctions varied by region and are thought to have been driven by varying combinations of human and climatic factors.[2] Human impact on megafauna populations is thought to have been driven by hunting ("overkill") as well as possibly also environmental alteration.[3][4][5] The relative importance of human vs climatic factors in the extinctions has been the subject of long-running controversy.[2]
Major extinctions were incurred in Australia-New Guinea (Sahul) beginning approximately 50,000 years ago and in the Americas about 13,000 years ago, coinciding in time with the early human migrations into these regions.[6][7][8] Extinctions in northern Eurasia were staggered over tens of thousands of years between 50,000 and 10,000 years ago,[1] while extinctions in the Americas were virtually simultaneous, spanning only 3000 years at most.[3][9] Overall, during Late Pleistocene about 65% of all megafaunal species worldwide became extinct,[10] rising to 83% in South America.[9]
The proportion of extinct large mammal species (more than or equal to 10 kg) in each country during the last 132 000 years, only counting extinctions earlier than 1000 years BP.jpg
The Late Pleistocene saw the extinction of many mammals weighing more than 40 kg. The proportion of megafauna extinctions is progressively larger the further the human migratory distance from Africa, with the highest extinction rates in Australia, and North and South America.
Extinctions in the Americas eliminated all mammals larger than 100 kg of South American origin, including those which migrated north in the Great American Interchange. It was only in Australia and the Americas that extinction occurred at family taxonomic levels or higher. This may relate to non-African megafauna and Homo sapiens not having evolved as species alongside each other. These continents had no known native species of Hominoidea (apes) at all, so no species of Hominidae (greater apes) or Homo.
The increased extent of extinction mirrors the migration pattern of modern humans: the further away from Africa, the more recently humans inhabited the area, the less time those environments (including its megafauna) had to become accustomed to humans (and vice versa).
There is no evidence of megafaunal extinctions at the height of the Last Glacial Maximum, suggesting that increased cold and glaciation were not factors in the Pleistocene extinction.[12]
There are three main hypotheses to explain this extinction:
climate change associated with the advance and retreat of major ice caps or ice sheets.
the extinction of the woolly mammoth allowed the extensive grassland to become birch forest, then subsequent forest fires changed the climate.[14]
There are some inconsistencies between the current available data and the prehistoric overkill hypothesis. For instance, there are ambiguities around the timing of sudden Australian megafauna extinctions.[13] Evidence supporting the prehistoric overkill hypothesis includes the persistence of megafauna on some islands for millennia past the disappearance of their continental cousins. For instance, ground sloths survived on the Antilles long after North and South American ground sloths were extinct, woolly mammoths died out on remote Wrangel Island 1,000 years after their extinction on the mainland, while Steller's sea cows persisted off the isolated and uninhabited Commander Islands for thousands of years after they had vanished from the continental shores of the north Pacific.[15] The later disappearance of these island species correlates with the later colonization of these islands by humans.
The original debates as to whether human arrival times or climate change constituted the primary cause of megafaunal extinctions necessarily were based on paleontological evidence coupled with geological dating techniques. Recently, genetic analyses of surviving megafaunal populations have contributed new evidence, leading to the conclusion: "The inability of climate to predict the observed population decline of megafauna, especially during the past 75,000 years, implies that human impact became the main driver of megafauna dynamics around this date."[16]
Recent research indicates that each species responded differently to environmental changes, and no one factor by itself explains the large variety of extinctions. The causes may involve the interplay of climate change, competition between species, unstable population dynamics, and human predation.[18]
Africa
Although Africa was one least affected regions, the region still suffered extinctions, particularly around the Late Pleistocene-Holocene transition. These extinctions were likely predominantly climatically driven by changes to grassland habitats.[19]
Palaeoloxodon iolensis? (other authors suggest that this taxon went extinct at the end of the Middle Pleistocene)
South, Southeast and Eastern Asia
Giant tapir (Tapirus augustus) restorationLife-sized models of StegodonPalaeoloxodon namadicus fossil at Indian Museum, Kolkata, IndiaFossil jaw (Xiahe mandible) of a denisovan
The timing of extinctions on the Indian subcontinent is uncertain due to a lack of reliable dating.[21] Similar issues have been reported for Chinese sites, though there is no evidence for any of the megafaunal taxa having survived into the Holocene in that region.[22] Extinctions in Southeast Asia and South China have been proposed to be the result of environmental shift from open to closed forested habitats.[23]
Saiga antelope (Saiga spp.) inhabited a range from England and France to Yukon in the Late Pleistocene, diversifying into two species. S. borealis is now extinct and the critically endangered S. tatarica is now limited to the steppe in Kazakhstan and MongoliaHippopotamuses (Hippopotamus spp.) inhabited Great Britain until 80,000 BCE, whence due to glacial shifts, hippopotamuses were restricted to southeastern Europe, Mediterranean islands and finally western Asia until 1,000 BCEReconstruction of the five phenotypes of Pleistocene wild horse. The coat colours and dimensions are based on genetic evidence and historic descriptionsElasmotherium sibiricum reconstructionCave paintings of the wooly rhinoceros (Coelodonta antiquitatis) in Chauvet-Pont-d'Arc Cave, FranceModern cheetah (Acinonyx jubatus) replaced giant cheetah (Acinonyx pardinensis) in Eurasia after the Middle Pleistocene and inhabited a range from eastern Europe and the Balkans to China . Today, the critically endangered Eurasian cheetah are now restricted to IranThe 'Gallery of Lions', representations of the Eurasian cave lion in Chauvet-Pont-d'Arc Cave, FranceThe leopard (Panthera pardus) inhabited the entire expanse of Afro-Eurasia below the 54th parallel north, from modern day Spain and the United Kingdom in the west, to South Africa in the south, and Siberia, Japan and Sundaland in the east during the Late PleistoceneCave bear (Ursus spelaeus) reconstructionThe woolly mammoth became extinct around 10,000 BCE – except for diminutive relict populations on St. Paul Island and Wrangel Island, which humans did not colonise until 3,600 BCE and 2,000 BCE respectivelyModels of the straight-tusked elephant (Paleoloxodon antiquus)
The Palearctic realm spans the entirety of the European continent and stretches into northern Asia, through the Caucasus and central Asia to northern China, Siberia and Beringia. During the Late Pleistocene, this region was noted for its great diversity and dynamism of biomes, including the warm climes of the Mediterranean basin, open temperate woodlands, arid plains, mountainous heathland and swampywetlands, all of which were vulnerable to the severe climatic fluctuations of the interchanges between glacial and interglacials periods (stadials). However, it was the expansive mammoth steppe which was the ecosystem which united and defined this region during the Late Pleistocene.[33] One of the key features of Europe's Late Pleistocene climate was the often drastic turnover of conditions and biota between the numerous stadials, which could set within a century. For example, during glacial periods, the entire North Sea was drained of water to form Doggerland. The final major cold spell occurred from 25,000 BCE to 18,000 BCE and is known as the Last Glacial Maximum, when the Fenno-Scandinavian ice sheet covered much of northern Europe, while the Alpine ice sheet occupied significant parts of central-southern Europe.
The first possible indications of habitation by hominins are the 7.2 million year old finds of Graecopithecus,[45] and 5.7 million year old footprints in Crete — however established habitation is noted in Georgia from 1.8 million years ago, proceeded to Germany and France, by Homo erectus.[46][47] Prominent co-current and subsequent species include Homo antecessor, Homo cepranensis, Homo heidelbergensis, neanderthals and denisovans,[48] preceding habitation by Homo sapiens circa 38,000 BCE. Extensive contact between African and Eurasian Homo groups is known at least in part through transfers of stone-tool technology in 500,000 BCE and again at 250,000 BCE.[49]
Neanderthals (Homo (sapiens) neanderthalensis; survived until about 40,000 years ago on the Iberian peninsula)
Many species extant today were present in areas either far to the south or west of their contemporary ranges. For example, all the arctic fauna on this list inhabited regions as south as the Iberian Peninsula at various stages of the Late Pleistocene. Recently extinct organisms are noted as †. Species extirpated from significant portions of or all former ranges in Europe and northern Asia during the Quaternary extinction event include-
Long-horned/Giant bison (Bos latifrons), fossil bison skeleton (public display, Cincinnati Museum of Natural History & Science, Cincinnati, Ohio, United States )Mounted skeleton of a shrub-ox (Euceratherium collinum)Life restoration of Cervalces scottiTetrameryx shuleri restorationA Chacoan peccary (Catagonus wagneri), believed to be the closest surviving relative of the extinct PlatygonusWestern camel (Camelops hesternus) reconstructionLife restoration of the Yukon horse (Equus lambei)Mixotoxodon larenis reconstructionSaber-toothed cat (Smilodon fatalis) reconstructionScimitar cat (Homotherium serum) reconstructionAmerican lion (Panthera atrox) reconstructionThe dhole (Cuon alpinus), now restricted to the southern portions of Asia, was present from Iberia to Mexico during the Late PleistoceneGiant short-faced bear (Arctodus simus) reconstructionAmerican mastodon (Mammut americanum) reconstructionColumbian mammoth (Mammuthus columbi) reconstructionGiant beaver (Castoroides ohioensis) skeleton displayed at the Field Museum of Natural History, Chicago , Illinois, United StatesSkull of Paralouatta marianae, one of the two Cuban members of the extinct Antilles monkeys (Xenotrichini)Eremotherium laurillardi skeleton displayed at the Houston Museum of Natural ScienceLife restoration of Nothrotheriops texanusGlyptotherium reconstructionCalifornian turkey (Meleagris californica) and megafaunal Californian condor (Gymnogyps amplus) fossil displays at La Brea Tar PitsTeratornis merriami skeleton from the La Brea Tar Pits in flight poseReconstruction of the Cuban giant owl (Ornimegalonyx oteroi), of Pleistocene Cuba, with the carcass of a large solenodon
During the last 60,000 years, including the end of the last glacial period, approximately 51 genera of large mammals have become extinct in North America. Of these, many 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 [citation needed]. In contrast, only about half a dozen small mammals disappeared during this time. Most other extinctions are poorly constrained in time, though some definitely occurred outside of this narrow interval.[78] For example, a genetic study published in 2021 indicates that horses, that were directly related to the modern horses, were still present in Yukon at least until 5,700 years ago or mid-Holocene.[79] Previous North American extinction pulses had occurred at the end of glaciations, but not with such an ecological 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. Such include the last native North American terror bird (Titanis), rhinoceros (Aphelops) and hyena (Chasmaporthetes). The extinction also had the effect of increasing homogenisation of large mammal communities between around 15,000 and 10,000 years ago.[80] Human habitation commenced unequivocally approximately 22,000 BCE north of the glacier,[81] and 13,500 BCE south,[82][83] however disputed evidence of southern human habitation exists from 130,000 BCE and 17,000 BCE onwards, described from sites in California and Meadowcroft in Pennsylvania.[84][85] Other prominent paleontological sites documenting human expansion into North America can be found in Mexico[84][86][87][88] and Panama, the crossroads of the American Interchange.[89]
North American extinctions (noted as herbivores (H) or carnivores (C)) included:
The survivors are in some ways as significant as the losses: bison (H), grey wolf (C), lynx (C), grizzly bear (C), American black bear (C), deer (e.g. caribou, moose, wapiti (elk), Odocoileus spp.) (H), pronghorn (H), white-lipped peccary (H), muskox (H), bighorn sheep (H), and mountain goat (H); the list of survivors also include species which were extirpated during the Quaternary extinction event, but recolonised at least part of their ranges during the mid-holocene from South American relict populations, such as the cougar (C), jaguar (C), giant anteater (C), collared peccary (H), ocelot (C) and jaguarundi (C). All save the pronghorns and giant anteaters were descended from Asian ancestors that had evolved with human predators.[119] 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 and so were geographically removed from human predators for a sizeable period of time.[120][121][122] Because ancient bison evolved into living bison,[123][124] 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 inconsistent with the overkill scenario. By the end of the Pleistocene, when humans first entered North America, these large animals had been geographically separated from intensive human hunting for more than 200,000 years. Given this enormous span of geologic time, bison 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-American culture associated with the Clovis people (q.v.), who were thought to use spear throwers to kill large animals. The chief criticism of the "prehistoric overkill hypothesis" has been that the human population at the time was too small and/or not sufficiently widespread geographically to have been capable of such ecologically significant impacts. This criticism does not mean that climate change scenarios explaining the extinction are automatically to be preferred by default, however, any more than weaknesses in climate change arguments can be taken as supporting overkill. Some form of a combination of both factors could be plausible, and overkill would be a lot easier to achieve large-scale extinction with an already stressed population due to climate change.
South America
Fossil skull of Hippidion, a genus of horse native to South America which went extinct in the early Holocene (6,000 BCE).Reconstruction of a Macrauchenia mother and calf, from Pleistocene South America.A Toxodon skull in an exhibition commemorating the 200th anniversary of Charles Darwin's birth, Esplanada dos Ministérios, BrasíliaReconstruction of the Dire wolf (Aenocyon dirus)Life restoration of Arctotherium bonariense.Cuvieronius reconstructionAn illustration of Megatherium.Doedicurus clavicaudatus reconstruction, distributed in the temperate savannah and woodland of South America.Fossil reconstruction of Panochthus frenzelianus with metal model.The disputed Late Pleistocene remains of a phorusrhacid in Uruguay are similar in size to the above Pliocene age Procariama simplex.
The Neotropical realm was affected by the fact that South America had been isolated as an island continent for many millions of years, and had a wide range of fauna found nowhere else, although many of them became extinct during the Great American Interchange about 3 million years ago, such as the Sparassodonta family. Those that survived the interchange included the ground sloths, glyptodonts, litopterns, pampatheres, phorusrhacids (terror birds) and notoungulates; all managed to extend their range to North America.[125][126][127] In the Pleistocene, South America remained largely unglaciated except for increased mountain glaciation in the Andes, which had a two-fold effect- there was a faunal divide between the Andes,[128][129] and the colder, arid interior resulted in the advance of temperate lowland woodland, tropical savanna and desert at the expense of rainforest.[130][131][132][133][134] Within these open environments, megafauna diversity was extremely dense, with over 40 genera recorded from the Guerrero member of Luján Formation alone.[135][136][137][138] Ultimately, by the mid-Holocene, all the preeminent genera of megafauna became extinct- the last specimens of Doedicurus and Toxodon have been dated to 4,555 BCE and 3,000 BCE respectively.[139][140][141][130] Their smaller relatives remain, including anteaters, tree sloths, armadillos; New World marsupials: opossums, shrew opossums, and the monito del monte (actually more related to Australian marsupials).[142] Intense human habitation was established circa 11,000 BCE, however partly disputed evidence of pre-clovis habitation occurs since 46,000 BCE and 20,000 BCE, such as at the Serra da Capivara National Park (Brazil) and Monte Verde (Chile) sites.[84][83][143] Today the largest land mammals remaining in South America are the wild camels of the Lamini group, such as the guanacos and vicuñas, and the genus Tapirus, of which Baird's tapir can reach up to 400 kg. Other notable surviving large fauna are peccaries, marsh deer (Capreolinae), giant anteaters, spectacled bears, maned wolves, pumas, ocelots, jaguars, rheas, emerald tree boas, boa constrictors, anacondas, American crocodiles, caimans, and giant rodents such as capybaras.
There exists two hypotheses regarding the extinction of the Australian megafauna, the first being that they went extinct with the arrival of the Aboriginal Australians on the continent, while he second hypothesis is that the Australian megafauna went extinct due to natural climate change. The main reason this theory exists is that there is evidence of megafauna surviving up until 40,000 years ago, a full 30,000 years after homo sapiens first landed in Australia. Implying that there was a significant period of homo sapiens and megafauna coexistence. Evidence of these animals existing at this time come from fossils records and ocean sediment. To begin with, sediment core drilled in the Indian Ocean off the coast of the southwest Australia indicate the existence of a fungus called Sporormiella which survived off the dung of plant eating mammals. The abundance of these spores in the sediment prior to 45,000 years ago indicates a lot of large mammals existed on the southwest Australian landscape up until that point. The sediment data also indicated that the megafauna population collapsed within a few thousand years around the 45,000 years ago suggesting a rapid extinction event.[170] In addition, fossils found at South Walker Creek, which is the youngest megafauna site in northern Australia, indicate that at least 16 species of megafauna survived there up until 40,000 years ago. Furthermore, there is no firm evidence of homo sapiens beings at South Walker Creek 40,000 years ago, therefore no human cause can be attributed to the extinction of these megafauna. However, there is evidence of major environmental deterioration of South Water Creek 40,000 years ago which the extinction can be attributed to. These changes include increased fire, reduction in grasslands, and the loss of freshwater.[171] The same environmental deterioration is seen across Australia at the time further strengthening the climate change argument. Australia’s climate at the time could best be described as an overall drying of the landscape due to less mean annual precipitation causing less freshwater availability and more drought conditions across the landscape. Overall, this led to changes in vegetation, increased fires, overall reduction in grasslands, and a greater competition for already scarce amount of freshwater.[172] In turn all these environmental changes proved to be too much for the Australian megafauna to cope with causing 90% of megafauna species to go extinct.
The third hypothesis shared by some scientists is that human impacts and natural climate changes led to the extinction of Australian megafauna. To begin with it is important to note that approximately 75% of Australia is semi-arid or arid landscape, therefore it makes sense that megafauna species utilized the same freshwater resources as humans. As a result, this could have increased the amount of megafauna hunted due to the competition for freshwater as the drought conditions persisted.[173] On top of the already dry conditions and diminishing grasslands, homo sapiens used fire agriculture to burn impassable land. This further diminished the already disappearing grassland which contained plants that were key dietary component of herbivorous megafauna. While there is no scientific consensus on the true cause of the extinction of Australian megafauna it is plausible that homo sapiens and natural climate change both had an impact because they were both in Australia at the time. Overall, there is an immense amount of evidence pointing to humans being the culprit but by ruling out climate change completely as a cause of the Australian megafauna extinction we are not getting the whole picture. The climate change that occurred in Australia 45,000 years ago destabilized the ecosystem making it particularly vulnerable to hunting and fire agriculture by humans; this is probably what led to the extinction of the Australian megafauna.
Procoptodon goliath reconstructionThe American flamingo (Phoenicopterus ruber) was one of four species of flamingo present in Australia in the Quaternary, all of which are now either extinct or extirpated. Australia is now the only inhabited continent in the world without flamingoes.Megalania skeleton, Melbourne Museum
In Sahul (a former continent composed of Australia and New Guinea), the sudden and extensive spate of extinctions occurred earlier than in the rest of the world.[174][175][176][177][178] Most evidence points to a 20,000 year period after human arrival circa 63,000 BCE,[179] but scientific argument continues as to the exact date range.[180] In the rest of the Pacific (other Australasian islands such as New Caledonia, and Oceania) although in some respects far later, endemic fauna also usually perished quickly upon the arrival of humans in the late Pleistocene and early Holocene. This section does only include extinctions that took place prior to European discovery of the respective islands.
There is no general agreement on where the Holocene, or anthropogenic, extinction begins, and the Quaternary extinction event ends, or if they should be considered separate events at all.[186][187] Some have suggested that anthropogenic extinctions may have begun as early as when the first modern humans spread out of Africa between 100,000 and 200,000 years ago, which is supported by rapid megafaunal extinction following recent human colonisation in Australia, New Zealand and Madagascar,[188] in a similar way that any large, adaptable predator moving into a new ecosystem would. In many cases, it is suggested even minimal hunting pressure was enough to wipe out large fauna, particularly on geographically isolated islands.[189][190] Only during the most recent parts of the extinction have plants also suffered large losses.[191]
Overall, the Holocene extinction can be characterised by the human impact on the environment. The Holocene extinction continues into the 21st century, with overfishing, ocean acidification and the amphibian crisis being a few broader examples of an almost universal, cosmopolitan decline of biodiversity.
Hunting hypothesis
A woolly mammoth hunt
The hunting hypothesis suggests that humans hunted megaherbivores to extinction, which in turn caused the extinction of carnivores and scavengers which had preyed upon those animals.[192][193][194] This hypothesis holds Pleistocene humans responsible for the megafaunal extinction. One variant, known as blitzkrieg, portrays this process as relatively quick. 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 without the earliest humans.
Despeciation within the genus Homo.Known H. sapiens migration routes in the Pleistocene.
Circumstantially, the close correlation in time between the appearance of humans in an area and extinction there provides weight for this scenario. The megafaunal extinctions covered a vast period of time and highly variable climatic situations. The earliest extinctions in Australia were complete approximately 50,000 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.[195][196]
This phenomenon appears even within regions. The mammal extinction wave in Australia about 50,000 years ago coincides not with known climatic changes, but with the arrival of humans. In addition, large mammal species like the giant kangaroo Protemnodon appear to have succumbed sooner on the Australian mainland than on Tasmania, which was colonised by humans a few thousand years later.[197][198]
Extinction through human hunting has been supported by archaeological finds of mammoths with projectile points embedded in their skeletons, by observations of modern naive animals allowing hunters to approach easily[199][200][201] and by computer models by Mosimann and Martin,[202] and Whittington and Dyke,[203] and most recently by Alroy.[204]
A study published in 2015 supported the hypothesis further by running several thousand scenarios that correlated the time windows in which each species is known to have become extinct with the arrival of humans on different continents or islands.[205] This was compared against climate reconstructions for the last 90,000 years.[205] The researchers found correlations of human spread and species extinction indicating that the human impact was the main cause of the extinction, while climate change exacerbated the frequency of extinctions.[205][206] The study, however, found an apparently low extinction rate in the fossil record of mainland Asia.[206]
Overkill hypothesis
The timing of extinctions follows the "March of Man"
The overkill hypothesis, a variant of the hunting hypothesis, was proposed in 1966 by Paul S. Martin,[207] Professor of Geosciences Emeritus at the Desert Laboratory of the University of Arizona.[208]
Objections to the hunting hypothesis
The major objections to the theory are as follows:
There is no archeological evidence that in North America megafauna other than mammoths, mastodons, gomphotheres and bison were hunted, despite the fact that, for example, camels and horses are very frequently reported in fossil history.[209] Overkill proponents, however, say this is due to the fast extinction process in North America and the low probability of animals with signs of butchery to be preserved.[210] A study by Surovell and Grund[211] concluded "archaeological sites dating to the time of the coexistence of humans and extinct fauna are rare. Those that preserve bone are considerably more rare, and of those, only a very few show unambiguous evidence of human hunting of any type of prey whatsoever."
Eugene S. Hunn points out that the birthrate in hunter-gatherer societies is generally too low, that too much effort is involved in the bringing down of a large animal by a hunting party, and that in order for hunter-gatherers to have brought about the extinction of megafauna simply by hunting them to death, an extraordinary amount of meat would have had to have been wasted.[212]
Climate change hypothesis
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 maximum would there be such extinctions. One study suggests that the Pleistocene megafaunal composition may have differed markedly from that of earlier interglacials, making the Pleistocene populations particularly vulnerable to changes in their environment.[213]
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 probably 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.[214][215][216]
Evidence in Southeast Asia, in contrast to Europe, Australia, and the Americas, suggests that climate change and an increasing sea level were significant factors in the extinction of several herbivorous species. Alterations in vegetation growth and new access routes for early humans and mammals to previously isolated, localized ecosystems were detrimental to select groups of fauna.[217]
Some evidence obtained from analysis of the tusks of mastodons from the American Great Lakes region appears inconsistent with the climate change hypothesis. Over a span of several thousand years prior to their extinction in the area, the mastodons show a trend of declining age at maturation. This is the opposite of what one would expect if they were experiencing stresses from deteriorating environmental conditions, but is consistent with a reduction in intraspecific competition that would result from a population being reduced by human hunting.[218]
Increased temperature
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.
A study covering the past 56,000 years indicates that rapid warming events with temperature changes of up to 16 °C (29 °F) had an important impact on the extinction of megafauna. Ancient DNA and radiocarbon data indicates that local genetic populations were replaced by others within the same species or by others within the same genus. Survival of populations was dependent on the existence of refugia and long distance dispersals, which may have been disrupted by human hunters.[219]
Arguments against the temperature hypothesis
Studies propose 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 most of the same large mammals survived similar temperature increases.[220][221][222][223][224][225]
In addition, numerous species such as mammoths on Wrangel Island[226] and St. Paul Island survived in human-free refugia despite changes in climate. This would not be expected if climate change were responsible (unless their maritime climates offered some protection against climate change not afforded to coastal populations on the mainland). 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.[citation needed]
Increased continentality affects vegetation in time or space
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.
Vegetation changes: geographic
It has been shown that vegetation changed from mixed woodland-parkland to separate prairie and woodland.[222][223][225] This may have affected the kinds of food 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.[227][228][229] 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.
Rainfall changes: time
Increased continentality resulted in reduced and less predictable rainfall limiting the availability of plants necessary for energy and nutrition.[230][231][232] Axelrod[233] and Slaughter[234] 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.[235]
In 2017 a study looked at the environmental conditions across Europe, Siberia and the Americas from 25,000–10,000 YBP. The study found that prolonged warming events leading to deglaciation and maximum rainfall occurred just prior to the transformation of the rangelands that supported megaherbivores into widespread wetlands that supported herbivore-resistant plants. The study proposes that moisture-driven environmental change led to the megafaunal extinctions and that Africa's trans-equatorial position allowed rangeland to continue to exist between the deserts and the central forests, therefore fewer megafauna species became extinct there.[219]
Arguments against the continentality hypotheses
Critics have identified a number of problems with the continentality hypotheses.
Megaherbivores have prospered at other times of continental climate. For example, megaherbivores thrived in Pleistocene Siberia, which had and has a more continental climate than Pleistocene or modern (post-Pleistocene, interglacial) North America.[236][237][238]
The animals that became extinct actually should have prospered during the shift from mixed woodland-parkland to prairie, because their primary food source, grass, was increasing rather than decreasing.[239][238][240] Although the vegetation did become more spatially specialized, the amount of prairie and grass available increased, which would have been good for horses and for mammoths, and yet they became extinct. This criticism ignores the increased abundance and broad geographic extent of Pleistocene Bison at the end of the Pleistocene, which would have increased competition for these resources in a manner not seen in any earlier interglacials.[213]
Although horses became extinct in the New World, they were successfully reintroduced by the Spanish in the 16th century—into a modern post-Pleistocene, interglacial climate. Today there are feral horses still living in those same environments. They find a sufficient mix of food to avoid toxins, they extract enough nutrition from forage to reproduce effectively and the timing of their gestation is not an issue. Of course, this criticism ignores the obvious fact that present-day horses are not competing for resources with ground sloths, mammoths, mastodons, camels, llamas, and bison. Similarly, mammoths survived the Pleistocene Holocene transition on isolated, uninhabited islands in the Mediterranean Sea[241] and on Wrangel Island in the Siberian Arctic[242] until 4,000 to 7,000 years ago.
Large mammals should have been able to migrate, permanently or seasonally, if they found the temperature too extreme, the breeding season too short, or the rainfall too sparse or unpredictable.[243] Seasons vary geographically. By migrating away from the equator, herbivores could have found areas with growing seasons more favorable for finding food and breeding successfully. Modern-day African elephants migrate during periods of drought to places where there is apt to be water.[244]
Large animals store more fat in their bodies than do medium-sized animals[245] and this should have allowed them to compensate for extreme seasonal fluctuations in food availability.
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 grasses and diverse flora and fauna can be supported.[246][247] 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.
Arguments against both climate change and overkill
It may be observed that neither the overkill nor the climate change hypotheses can fully explain events: browsers, mixed feeders and non-ruminant grazer species suffered most, while relatively more ruminant grazers survived.[248] However, a broader variation of the overkill hypothesis may predict this, because changes in vegetation wrought by either Second Order Predation (see below)[249][250] or anthropogenic fire preferentially selects against browse species.[citation needed]
Hyperdisease hypothesis
Theory
The hyperdisease hypothesis, as advanced by Ross D. E. MacFee and Preston A. Marx, attributes the extinction of large mammals during the late Pleistocene to indirect effects of the newly arrived aboriginal humans.[251][252][253] 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.[251]
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.[citation needed]
One suggestion is that pathogens were transmitted by the expanding humans via the domesticated dogs they brought with them,[254] though this does not fit the timeline of extinctions in the Americas and Australia in particular.
Arguments against the hyperdisease hypothesis
Generally speaking, disease has to be very virulent to kill off all the individuals in a genus or species. Even such a virulent disease as West Nile fever is unlikely to have caused extinction.[255]
The disease would need to be implausibly selective while being simultaneously implausibly broad. Such a disease needs to be capable of killing off wolves such as Canis dirus or goats such as Oreamnos harringtoni while leaving other very similar species (Canis lupus and Oreamnos americanus, respectively) unaffected. It would need to be capable of killing off flightless birds while leaving closely related flighted species unaffected. Yet while remaining sufficiently selective to afflict only individual species within genera it must be capable of fatally infecting across such clades as birds, marsupials, placentals, testudines, and crocodilians. No disease with such a broad scope of fatal infectivity is known, much less one that remains simultaneously incapable of infecting numerous closely related species within those disparate clades. On the other hand, this objection does not account for the possibility of a variety of different diseases being introduced around the same era.[citation needed]
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 there it would require that the population remain immunologically naive despite this constant transmission of genetic and pathogenic material.[citation needed]
The dog-specific hypothesis cannot account for several major extinction events, notably the Americas (for reasons already covered) and Australia. Dogs did not arrive in Australia until approximately 35,000 years after the first humans arrived there, and approximately 30,000 years after the Australian megafaunal extinction was complete.[citation needed]
The Second-Order Predation Hypothesis says that as humans entered the New World they continued their policy of killing predators, which had been successful in the Old World but because they were more efficient and because the fauna, both herbivores and carnivores, were more naive, they killed off enough carnivores to 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:
After the arrival of H. sapiens in the New World, existing predators must share the prey populations with this new predator. Because of this competition, populations of original, or first-order, predators cannot find enough food; they are in direct competition with humans.
Second-order predation begins as humans begin to kill predators.
Prey populations are no longer well controlled by predation. Killing of nonhuman predators by H. sapiens reduces their numbers to a point where these predators no longer regulate the size of the prey populations.
Lack of regulation by first-order predators triggers boom-and-bust cycles in prey populations. Prey populations expand and consequently overgraze and over-browse the land. Soon the environment is no longer able to support them. As a result, many herbivores starve. Species that rely on the slowest recruiting food become extinct, followed by species that cannot extract the maximum benefit from every bit of their food.
Boom-bust cycles in herbivore populations change the nature of the vegetative environment, with consequent climatic impacts on relative humidity and continentality. Through overgrazing and overbrowsing, mixed parkland becomes grassland, and climatic continentality increases.
Support
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[256][257] (results graph at left).
The Pleistocene extinction model 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.[249] (results graph at right).
The second-order predation hypothesis is supported by the observation above that there was a massive increase in bison populations.[258]
Arguments against the second-order predation hypothesis
The multispecies model produces a mass extinction through indirect competition between herbivore species: small species with high reproductive rates subsidize predation on large species with low reproductive rates.[204] All prey species are lumped in the Pleistocene extinction model.
The control of population sizes by predators is not fully supported by observations of modern ecosystems.[259]
Arguments against the second-order predation plus climate hypothesis
It assumes decreases in vegetation due to climate change, but deglaciation doubled the habitable area of North America.
Any vegetational changes that did occur failed to cause almost any extinctions of small vertebrates, and they are more narrowly distributed on average.
↑Dembitzer, Jacob; Barkai, Ran; Ben-Dor, Miki; Meiri, Shai (2022-01-15). "Levantine overkill: 1.5 million years of hunting down the body size distribution". Quaternary Science Reviews276: 107316. doi:10.1016/j.quascirev.2021.107316. Bibcode: 2022QSRv..27607316D.
↑Koch, Paul L.; Barnosky, Anthony D. (2006-01-01). "Late Quaternary Extinctions: State of the Debate". Annual Review of Ecology, Evolution, and Systematics37 (1): 215–250. doi:10.1146/annurev.ecolsys.34.011802.132415.
↑Putshkov, P. V. (1997). "Were the Mammoths killed by the warming? (Testing of the climatic versions of the Wurm extinctions)". Vestnik Zoologii (Supplement No.4).
↑Rabanus-Wallace, M. Timothy; Wooller, Matthew J.; Zazula, Grant D.; Shute, Elen; Jahren, A. Hope; Kosintsev, Pavel; Burns, James A.; Breen, James et al. (2017). "Megafaunal isotopes reveal role of increased moisture on rangeland during late Pleistocene extinctions". Nature Ecology & Evolution1 (5): 0125. doi:10.1038/s41559-017-0125. PMID28812683.
↑Grayson, Donald K.; Meltzer, David J. (2002). "Clovis Hunting and Large Mammal Extinction: A Critical Review of the Evidence". Journal of World Prehistory16 (4): 313–359. doi:10.1023/A:1022912030020.
↑Anderson, Paul K. (July 1995). "Competition, Predation, and the Evolution and Extinction of Steller's Sea Cow, Hydrodamalis Gigas". Marine Mammal Science11 (3): 391–4. doi:10.1111/j.1748-7692.1995.tb00294.x.
↑Holliday, Vance T.; Bartlein, Patrick J.; Scott, Andrew C.; Marlon, Jennifer R., WikidataQ91978737
↑Lan, Tianying; Lindqvist, Charlotte (2018). "Paleogenomics: Genome-Scale Analysis of Ancient DNA and Population and Evolutionary Genomic Inferences". in Lindqvist, C.; Rajora, O.. Population Genomics. pp. 323–360. doi:10.1007/13836_2017_7. ISBN978-3-030-04587-6.
↑Rozzi, Roberto (2017-02-01). "A new extinct dwarfed buffalo from Sulawesi and the evolution of the subgenus Anoa: An interdisciplinary perspective". Quaternary Science Reviews157: 188–205. doi:10.1016/j.quascirev.2016.12.011. Bibcode: 2017QSRv..157..188R.
↑Jukar, Advait M.; Patnaik, Rajeev; Chauhan, Parth R.; Li, Hong-Chun; Lin, Jih-Pai (2019-09-10). "The youngest occurrence of Hexaprotodon Falconer and Cautley, 1836 (Hippopotamidae, Mammalia) from South Asia with a discussion on its extinction". Quaternary International. AMS 14C Applications II 528: 130–137. doi:10.1016/j.quaint.2019.01.005. ISSN1040-6182. Bibcode: 2019QuInt.528..130J.
↑Adams, J. M.; Faure, H.; Faure-Denard, L.; McGlade, J. M.; Woodward, F. I. (1990-12-27). "Increases in terrestrial carbon storage from the Last Glacial Maximum to the present". Nature348 (6303): 711–714. doi:10.1038/348711a0. Bibcode: 1990Natur.348..711A.
↑Álvarez-Lao, Diego J.; García, Nuria (2011-03-15). "Geographical distribution of Pleistocene cold-adapted large mammal faunas in the Iberian Peninsula". Quaternary International. Quaternary Floral and Faunal Assemblages: Ecological and Taphonomical Investigations 233 (2): 159–170. doi:10.1016/j.quaint.2010.04.017. Bibcode: 2011QuInt.233..159A.
↑ 39.039.139.239.339.4Vereshchagin, N. K.; Baryshnikov, G. F. (1991-01-01). "The ecological structure of the "Mammoth Fauna" in Eurasia". Annales Zoologici Fennici28 (3/4): 253–259.
↑Gierliński, Gerard D.; Niedźwiedzki, Grzegorz; Lockley, Martin G.; Athanassiou, Athanassios; Fassoulas, Charalampos; Dubicka, Zofia; Boczarowski, Andrzej; Bennett, Matthew R. et al. (2017). "Possible hominin footprints from the late Miocene (c. 5.7 Ma) of Crete?". Proceedings of the Geologists' Association128 (5–6): 697–710. doi:10.1016/j.pgeola.2017.07.006. Bibcode: 2017PrGA..128..697G.
↑Owen-Smith, R.N. (1992). Megaherbivores: The influence of very large body size on ecology. Cambridge studies in ecology. Cambridge: Cambridge Univ. Press. ISBN978-0-521-42637-4.
↑Whitney-Smith, E. (2006). Clovis and Extinctions – Overkill, Second Order Predation, Environmental Degradation in a Non-equilibrium Ecosystem "Clovis Age Continent". University of New Mexico Press.
↑ 53.053.1Rivals, Florent (2006). "Découverte de Capra caucasica et d'Hemitragus cedrensis (Mammalia, Bovidae) dans les niveaux du Pléistocène supérieur de la Caune de l'Arago (Tautavel, France): Implication biochronologique dans le contexte du Bassin Méditerranéen". Geobios39 (1): 85–102. doi:10.1016/j.geobios.2004.08.004. Bibcode: 2006Geobi..39...85R.
↑ 54.054.1Creégut-Bonnoure, Evelyne (12 March 2009). "Biochronologie et grands mammifères au Pléistocène moyen et supérieur en Europe occidentale: l'Apport des genres hemitragus et capra" (in fr). Quaternaire20: 481–508. doi:10.4000/quaternaire.5345.
↑Baryshnikov, G.; Tikhonov, A. (1994-10-01). "Notes on skulls of Pleistocene Saiga of Northern Eurasia". Historical Biology8 (1–4): 209–234. doi:10.1080/10292389409380478.
↑Sanz, Montserrat; Daura, Joan; Brugal, Jean-Philip (2014-01-01). "First occurrence of the extinct deer Haploidoceros in the Iberian Peninsula in the Upper Pleistocene of the Cova del Rinoceront (Castelldefels, Barcelona)". Comptes Rendus Palevol13 (1): 27–40. doi:10.1016/j.crpv.2013.06.005. Bibcode: 2014CRPal..13...27S.
↑Rivals, Florent; Sanz, Montserrat; Daura, Joan (2016-05-01). "First reconstruction of the dietary traits of the Mediterranean deer (Haploidoceros mediterraneus) from the Cova del Rinoceront (NE Iberian Peninsula)". Palaeogeography, Palaeoclimatology, Palaeoecology449: 101–107. doi:10.1016/j.palaeo.2016.02.014. Bibcode: 2016PPP...449..101R.
↑ 62.062.162.2Foronova, I. (2006). "Late quaternary equids (genus Equus) of South-western and South-central Siberia". in M. Mashkour. Equids in time and space. Papers in honour of Véra Eisenmann. Proceedings of the 9th conference of the International Council of Archaeozoology, Durham, August 2002. Oxbow Books. pp. 20–30.
↑Lu, Dan; Yang, Yangheshan; Li, Qiang; Ni, Xijun (2021-07-30). "A late Pleistocene fossil from Northeastern China is the first record of the dire wolf (Carnivora: Canis dirus) in Eurasia". Quaternary International. Cave Deposits from Luotuo Hill, Northeast China: A Geochronologically Calibrated Mammalian Biostratigraphic Standard for the Quaternary of Eastern Asia 591: 87–92. doi:10.1016/j.quaint.2020.09.054. ISSN1040-6182. Bibcode: 2021QuInt.591...87L.
↑Marciszak, Adrian; Schouwenburg, Charles; Lipecki, Grzegorz; Talamo, Sahra; Shpansky, Andrey; Malikov, Dmitriy; Gornig, Wiktoria (2019-12-01). "Steppe brown bear Ursus arctos "priscus" from the Late Pleistocene of Europe". Quaternary International. Quaternary Stratigraphy and Hominids Around Europe:: SEQS 2017 Meeting 534: 158–170. doi:10.1016/j.quaint.2019.02.042. ISSN1040-6182. Bibcode: 2019QuInt.534..158M.
↑Münzel, Susanne C.; Rivals, Florent; Pacher, Martina; Döppes, Doris; Rabeder, Gernot; Conard, Nicholas J.; Bocherens, Hervé (2014-08-07). "Behavioural ecology of Late Pleistocene bears (Ursus spelaeus, Ursus ingressus): Insight from stable isotopes (C, N, O) and tooth microwear". Quaternary International. Fossil remains in karst and their role in reconstructing Quaternary paleoclimate and paleoenvironments 339–340: 148–163. doi:10.1016/j.quaint.2013.10.020. Bibcode: 2014QuInt.339..148M.
↑Ghezzo, Elena; Boscaini, Alberto; Madurell-Malapeira, Joan; Rook, Lorenzo (2014-12-16). "Lynx remains from the Pleistocene of Valdemino cave (Savona, Northwestern Italy), and the oldest occurrence of Lynx spelaeus (Carnivora, Felidae)". Rendiconti Lincei26 (2): 87–95. doi:10.1007/s12210-014-0363-4.
↑Anthony D. Barnosky; Paul L. Koch; Robert S. Feranec; Scott L. Wing; Alan B. Shabel (2004). "Assessing the Causes of Late Pleistocene Extinctions on the Continents". Science306 (5693): 70–75. doi:10.1126/science.1101476. PMID15459379. Bibcode: 2004Sci...306...70B.
↑Waters, Michael R.; Forman, Steven L.; Jennings, Thomas A.; Nordt, Lee C.; Driese, Steven G.; Feinberg, Joshua M.; Keene, Joshua L.; Halligan, Jessi et al. (2011-03-25). "The Buttermilk Creek Complex and the Origins of Clovis at the Debra L. Friedkin Site, Texas". Science331 (6024): 1599–1603. doi:10.1126/science.1201855. ISSN0036-8075. PMID21436451. Bibcode: 2011Sci...331.1599W.
↑Palma-Ramírez, Arturo; Goyenechea, Irene; Castillo-Cerón, Jesús M. (2014-12-01). "Panbiogeography of the Santa María Amajac area, Hidalgo, Mexico". Revista Mexicana de Biodiversidad85 (4): 1228–1234. doi:10.7550/rmb.44392.
↑Fox-Dobbs, Kena; Leonard, Jennifer A.; Koch, Paul L. (2008). "Pleistocene megafauna from eastern Beringia: Paleoecological and paleoenvironmental interpretations of stable carbon and nitrogen isotope and radiocarbon records". Palaeogeography, Palaeoclimatology, Palaeoecology261 (1–2): 30–46. doi:10.1016/j.palaeo.2007.12.011. Bibcode: 2008PPP...261...30F.
↑Youngman, Phillip M. (1986-03-01). "The extinct short-faced skunk Brachyprotoma obtusata (Mammalia, Carnivora): first records for Canada and Beringia". Canadian Journal of Earth Sciences23 (3): 419–424. doi:10.1139/e86-043. Bibcode: 1986CaJES..23..419Y.
↑Alberdi, María Teresa; Juárez-Woo, Javier; Polaco, Oscar J.; Arroyo-Cabrales, Joaquín (2009-02-01). "Description of the most complete skeleton of Stegomastodon (Mammalia, Gomphotheriidae) recorded for the Mexican Late Pleistocene". Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen251 (2): 239–255. doi:10.1127/0077-7749/2009/0251-0239.
↑McDonald, H. Gregory; Chatters, James C.; Gaudin, Timothy J. (2017-05-04). "A new genus of megalonychid ground sloth (Mammalia, Xenarthra) from the late Pleistocene of Quintana Roo, Mexico". Journal of Vertebrate Paleontology37 (3): e1307206. doi:10.1080/02724634.2017.1307206. ISSN0272-4634. Bibcode: 2017JVPal..37E7206M.
↑Stinnesbeck, Sarah R.; Frey, Eberhard; Olguín, Jerónimo Avíles; Stinnesbeck, Wolfgang; Zell, Patrick; Mallison, Heinrich; González, Arturo González; Núñez, Eugenio Aceves et al. (2017-06-01). "Xibalbaonyx oviceps, a new megalonychid ground sloth (Folivora, Xenarthra) from the Late Pleistocene of the Yucatán Peninsula, Mexico, and its paleobiogeographic significance". PalZ91 (2): 245–271. doi:10.1007/s12542-017-0349-5. ISSN0031-0220.
↑MacPhee, R.D.E. (1999). Extinctions in Near Time: Causes, Contexts, and Consequences. Kluwer Academic Publishers. ISBN978-0-306-46092-0.[page needed]
↑Bell, C.J. (2004). "The Blancan, Irvingtonian, and Rancholabrean mammal ages". in Woodburne, M.O.. Late Cretaceous and Cenozoic Mammals of North America: Biostratigraphy and Geochronology. New York: Columbia Univ. Press. pp. 232–314. ISBN978-0-231-13040-0.
↑Scott, E.; Cox, S.M. (2008). "Late Pleistocene distribution of Bison (Mammalia; Artiodactyla) in the Mojave Desert of Southern California and Nevada". in Wang, X.. Geology and Vertebrate Paleontology of Western and Southern North America. Los Angeles: Natural History Museum of Los Angeles County. pp. 359–382.
↑Sanders, A.E.; R.E. Weems; L.B. Albright III (2009). "Formalization of the mid-Pleistocene "Ten Mile Hill beds" in South Carolina with evidence for placement of the Irvingtonian–Rancholabrean boundary". in Albright III, L.B.. Papers on Geology, Vertebrate Paleontology, and Biostratigraphy in Honor of Michael O. Woodburne. Flagstaff: Museum of Northern Arizona. pp. 369–375.
↑Wilson, M.C.; L.V. Hills; B. Shapiro (2008). "Late Pleistocene northward-dispersing Bos antiquus from the Bighill Creek Formation, Gallelli Gravel Pit, Alberta, Canada, and the fate of Bison occidentalis". Canadian Journal of Earth Sciences45 (7): 827–859. doi:10.1139/E08-027. Bibcode: 2008CaJES..45..827W.
↑ 132.0132.1132.2132.3Oliveira, Édison V.; Porpino, Kleberson O.; Barreto, Alcina F. (2010). "On the presence of Glyptotherium in the Late Pleistocene of Northeastern Brazil, and the status of "Glyptodon" and "Chlamydotherium". Paleobiogeographic implications". Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen258 (3): 353–363. doi:10.1127/0077-7749/2010/0116.
↑Cione, Alberto L.; Tonni, Eduardo P.; Soibelzon, Leopoldo (2009). "Did Humans Cause the Late Pleistocene-Early Holocene Mammalian Extinctions in South America in a Context of Shrinking Open Areas?". American Megafaunal Extinctions at the End of the Pleistocene. Vertebrate Paleobiology and Paleoanthropology. Springer, Dordrecht. pp. 125–144. doi:10.1007/978-1-4020-8793-6_7. ISBN978-1-4020-8792-9.
↑Hubbe, A.; Hubbe, M.; Neves, W. (2007-09-01). "Early Holocene survival of megafauna in South America". Journal of Biogeography34 (9): 1642–1646. doi:10.1111/j.1365-2699.2007.01744.x. ISSN1365-2699.
↑Pereira, Jamil Corrêa; Lopes, Renato Pereira; Kerber, Leonardo (2012). "New remains of Late Pleistocene mammals from the Chuí Creek, Southern Brazil". Revista Brasileira de Paleontologia15 (2): 228–239. doi:10.4072/rbp.2012.2.10.
↑Gaudioso, Pablo Javier; Gasparini, Germán M.; Herbst, Rafael; Barquez, Rubén Mario (2017-03-16). "First record of the Neolicaphrium recens Frenguelli, 1921 (Mammalia, Litopterna) in the Pleistocene of Santiago del Estero Province, Argentina". Papéis Avulsos de Zoologia57 (3): 23–29. doi:10.11606/0031-1049.2017.57.03. ISSN1807-0205.
↑Prevosti, F. J.; Tonni, E. P.; Bidegain, J. C. (2009-12-01). "Stratigraphic range of the large canids (Carnivora, Canidae) in South America, and its relevance to quaternary biostratigraphy". Quaternary International. The Ensenadan Stage/Age in southern South America 210 (1): 76–81. doi:10.1016/j.quaint.2009.06.034. ISSN1040-6182. Bibcode: 2009QuInt.210...76P.
↑Jones, Washington; Rinderknecht, Andrés; Alvarenga, Herculano; Montenegro, Felipe; Ubilla, Martín (2017-12-30). "The last terror birds (Aves, Phorusrhacidae): new evidence from the late Pleistocene of Uruguay". PalZ92 (2): 365–372. doi:10.1007/s12542-017-0388-y. ISSN0031-0220.
↑Alvarenga, Herculano; Jones, Washington; Rinderknecht, Andrés (2010-05-01). "The youngest record of phorusrhacid birds (Aves, Phorusrhacidae) from the late Pleistocene of Uruguay". Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen256 (2): 229–234. doi:10.1127/0077-7749/2010/0052.
↑Agnolin, Federico (2013). "La posición sistemática de Hermosiornis (Aves, Phororhacoidea) y sus implicancias filogenéticas". Revista del Museo Argentino de Ciencias Naturales. Nueva Series 15 (1): 39–60. doi:10.22179/revmacn.15.167. ISSN1853-0400.
↑Suárez, William; Olson, Storrs L. (2014-09-01). "A new fossil species of small crested caracara (Aves: Falconidae: Caracara) from the Pacific lowlands of western South America". Proceedings of the Biological Society of Washington127 (2): 299–310. doi:10.2988/0006-324X-127.2.299. ISSN0006-324X.
↑Bayly, I. A. E. (1993). "The fauna of athalassic saline waters in Australia and the Altiplano of South America: Comparisons and historical perspectives". in Hurlbert, Stuart H.. Saline Lakes V. Developments in Hydrobiology. 87. Springer Netherlands. pp. 225–231. doi:10.1007/978-94-011-2076-0_18. ISBN9789401049214.
↑Doughty, C. E.; Wolf, A.; Field, C. B. (2010). "Biophysical feedbacks between the Pleistocene megafauna extinction and climate: The first human‐induced global warming?". Geophys. Res. Lett.37 (15): L15703. doi:10.1029/2010GL043985. Bibcode: 2010GeoRL..3715703D.
↑Grayson, Donald K.; Meltzer, David J. (December 2012). "Clovis Hunting and Large Mammal Extinction: A Critical Review of the Evidence". Journal of World Prehistory16 (4): 313–359. doi:10.1023/A:1022912030020.
↑Kolbert, Elizabeth (2014). The Sixth Extinction: An Unnatural History. Bloomsbury Publishing. ISBN9781408851210.
↑Perry, George L. W.; Wheeler, Andrew B.; Wood, Jamie R.; Wilmshurst, Janet M. (2014-12-01). "A high-precision chronology for the rapid extinction of New Zealand moa (Aves, Dinornithiformes)". Quaternary Science Reviews105: 126–135. doi:10.1016/j.quascirev.2014.09.025. Bibcode: 2014QSRv..105..126P.
↑Crowley, Brooke E. (2010-09-01). "A refined chronology of prehistoric Madagascar and the demise of the megafauna". Quaternary Science Reviews. Special Theme: Case Studies of Neodymium Isotopes in Paleoceanography 29 (19–20): 2591–2603. doi:10.1016/j.quascirev.2010.06.030. Bibcode: 2010QSRv...29.2591C.
↑Martin P. S. (1963). The last 10,000 years: A fossil pollen record of the American Southwest. Tucson, AZ: Univ. Ariz. Press. ISBN978-0-8165-1759-6.
↑Martin P. S. (1967). "Prehistoric overkill". in Martin, P. S.. Pleistocene extinctions: The search for a cause. New Haven: Yale Univ. Press. ISBN978-0-300-00755-8.
↑Martin P. S. (1989). "Prehistoric overkill: A global model". in Martin, P.S.. Quaternary extinctions: A prehistoric revolution. Tucson, AZ: Univ. Arizona Press. pp. 354–404. ISBN978-0-8165-1100-6.
↑Diamond, J. (1984). "Historic extinctions: a Rosetta stone for understanding prehistoric extinctions". in Martin, P.S.. Quaternary extinctions: A prehistoric revolution. Tucson, AZ: Univ. Arizona Press. pp. 824–62. ISBN978-0-8165-1100-6.
↑Diamond, J. (1997). Guns, germs, and steel; the fates of human societies. New York: Norton. ISBN978-0-393-31755-8.
↑Mossiman, J. E.; Martin, P. S. (1975). "Simulating Overkill by Paleoindians". American Scientist63 (3): 304–13. Bibcode: 1975AmSci..63..304M.
↑Whittington, S. L.; Dyke, B. (1984). "Simulating overkill: experiment with the Mossiman and Martin model". in Martin, P.S.. Quaternary extinctions: A prehistoric revolution. Tucson, AZ: Univ. Arizona Press. pp. 451–66. ISBN978-0-8165-1100-6.
↑Fiedel, S.; Haynes, G. (2004). "A premature burial: comments on Grayson and Meltzer's Requiem for overkill". Journal of Archaeological Science31 (1): 121–131. doi:10.1016/j.jas.2003.06.004. Bibcode: 2004JArSc..31..121F.
↑Surovell, Todd A; Brigid S Grund (2012). "The associational critique of Quaternary overkill". American Antiquity77 (4): 673–688. doi:10.7183/0002-7316.77.4.672.
↑Nadasdy, Paul (2006). "Transcending the Debate over the Ecologically Noble Indian: Indigenous Peoples and Environmentalism". Ethnohistory52 (2): 291–331. doi:10.1215/00141801-52-2-291.
↑ 213.0213.1Scott, E. (2010). "Extinctions, scenarios, and assumptions: Changes in latest Pleistocene large herbivore abundance and distribution in western North America". Quaternary International217 (1–2): 225–239. doi:10.1016/j.quaint.2009.11.003. Bibcode: 2010QuInt.217..225S.
↑Presenter: Willis, Paul; Producer: Bryce, Clay; Producer: Searle, Mike (17 August 2006). "Thylacoleo "The Beast of the Nullarbor"". Catalyst. Australian Broadcasting Commission. Archived from the original on 2020-09-30.
↑Fisher, Daniel C. (2009). "Paleobiology and Extinction of Proboscideans in the Great Lakes Region of North America". in Haynes, Gary. American Megafaunal Extinctions at the End of the Pleistocene. Vertebrate Paleobiology and Paleoanthropology. Springer. pp. 55–75. doi:10.1007/978-1-4020-8793-6_4. ISBN978-1-4020-8792-9.
↑ 219.0219.1Rabanus-Wallace, M. Timothy; Wooller, Matthew J.; Zazula, Grant D.; Shute, Elen; Jahren, A. Hope; Kosintsev, Pavel; Burns, James A.; Breen, James et al. (2017). "Megafaunal isotopes reveal role of increased moisture on rangeland during late Pleistocene extinctions". Nature Ecology & Evolution1 (5): 0125. doi:10.1038/s41559-017-0125. PMID28812683.
↑Andersen, S. T (1973). "The differential pollen productivity of trees and its significance for the interpretation of a pollen diagram from a forested region". in Birks, H.J.B.. Oxford: Blackwell Scientific. ISBN0-632-09120-7.
↑ 222.0222.1Birks, H.H. (1973). "Modern macrofossil assemblages in lake sediments in Minnesota". in Birks, H.J.B.. Oxford: Blackwell Scientific. ISBN0-632-09120-7.
↑ 225.0225.1Davis, M. B. (1976). "Pleistocene biogeography of temperate deciduous forests". Geoscience and man: Ecology of the Pleistocene. 13. Baton Rouge: School of Geoscience, Louisiana State Univ..
↑Guthrie, R. D. (1988). Frozen Fauna of the Mammoth Steppe: The Story of Blue Babe. University Of Chicago Press. ISBN978-0-226-31122-7.
↑Guthrie, R. D. (1989). "Mosaics, allochemics, and nutrients: an ecological theory of Late Pleistocene megafaunal extinctions". in Martin, P.S.. Quaternary extinctions: A prehistoric revolution. Tucson, AZ: Univ. Arizona Press. pp. 259–99. ISBN978-0-8165-1100-6.
↑Hoppe, P.P. (1978). "Rumen fermentation in African ruminants". Atlanta.
↑Graham, R.W.; Lundelius, E.L. (1989). "Coevolutionary disequilibrium and Pleistocene extinctions". in Martin, P.S.. Quaternary extinctions: A prehistoric revolution. Tucson, AZ: Univ. Arizona Press. pp. 354–404. ISBN978-0-8165-1100-6.
↑King, J.E.; Saunders, J.J. (1989). "Environmental insularity and the extinction of the American mastodont". in Martin, P.S.. Quaternary extinctions: A prehistoric revolution. Tucson, AZ: Univ. Arizona Press. pp. 354–404. ISBN978-0-8165-1100-6.
↑Axelrod, D. I. (1967). "Quaternary extinctions of large mammals". University of California Publications in Geological Sciences74: 1–42. ASIN B0006BX8LG.
↑Slaughter, B. H. (1967). "Animal ranges as a clue to late-Pleistocene extinction". in Martin, P.S.. Pleistocene extinctions: The search for a cause. New Haven: Yale Univ. Press. ISBN978-0-300-00755-8.
↑Kilti, R. A. (1988). "Seasonality, gestation time, and large mammal extinctions". in Martin, P.S.. Quaternary extinctions: A prehistoric revolution. Tucson, AZ: Univ. Arizona Press. pp. 354–404. ISBN978-0-8165-1100-6.
↑ 238.0238.1McDonald, J. (1989). "The reordered North American selection regime and late Quaternary megafaunal extinctions". in Martin, P.S.. Quaternary extinctions: A prehistoric revolution. Tucson, AZ: Univ. Arizona Press. pp. 354–404. ISBN978-0-8165-1100-6.
↑Birks, H.J.B.; West, R.G. (1973). "A Symposium of the British Ecological Society". Oxford: Blackwell Scientific. ISBN0-632-09120-7.
↑McDonald, J. (1981). North American Bison: Their classification and evolution. Berkeley: Univ. Calif. Press. ISBN978-0-520-04002-1.
↑Burney, D. A. (1993). "Recent animal extinctions: recipes for disaster". American Scientist81 (6): 530–41. Bibcode: 1993AmSci..81..530B.
↑Pennycuick, C.J. (1979). "Energy costs of locomotion and the concept of "Foraging radius"". Serengetti: Dynamics of an Ecosystem. Chicago: Univ. Chicago Press. pp. 164–85. ISBN978-0-226-76029-2.
↑Owen-Smith, R.N. (1992). Megaherbivores: The influence of very large body size on ecology. Cambridge studies in ecology. Cambridge: Cambridge Univ. Press. ISBN978-0-521-42637-4.
↑ 249.0249.1Whitney-Smith, E. (2006). Clovis and Extinctions – Overkill, Second Order Predation, Environmental Degradation in a Non-equilibrium Ecosystem "Clovis Age Continent". University of New Mexico Press.
↑ 251.0251.1MacFee, Ross D. E.; Marx, Preston A. (1997). "Humans, hyperdisease and first-contact extinctions". in Goodman, S.; Patterson, B. D.. Natural Change and Human Impact in Madagascar. Washington DC: Smithsonian Press. pp. 169–217. ISBN978-1-56098-683-6.
↑MacFee, Ross D. E.; Marx, Preston A. (1997). "The 40,000-year Plague: Humans, Hyperdisease, and First-contact Extinctions". Washington DC: Smithsonian Institution Press. pp. 169–217.
↑Whitney-Smith, E. (2004). "Late Pleistocene extinctions through second-order predation". in Barton, C.M.. Settlement of the American Continents: A Multidisciplinary Approach to Human Biogeography. Tucson, AZ: University of Arizona Press. ISBN978-0-8165-2323-8.
↑Whitney-Smith, E. (2009). The Second-Order Predation Hypothesis of Pleistocene Extinctions: A System Dynamics Model. Saarbruken, Germany: VDM Verlag. ISBN978-3-639-11579-6.
↑Scott, E. (2010). "Extinctions, scenarios, and assumptions: Changes in latest Pleistocene large herbivore abundance and distribution in western North America". Quat. Int.