Pleistocene extinction

The Quaternary period (from 2.588 ± 0.005 million years ago to the present) has seen the extinctions of numerous predominantly megafaunal species, which have resulted in a collapse in faunal density and diversity and the extinction of key ecological strata across the globe. The most prominent event in the Late Pleistocene is differentiated from previous Quaternary pulse extinctions by the widespread absence of ecological succession to replace these extinct species, and the regime shift of previously established faunal relationships and habitats as a consequence.

The earliest casualties were incurred at 130,000 BCE (the start of the Late Pleistocene), in Australia ~ 60,000 years ago, in Americas ~ 15,000 years ago, coinciding in time with the early human migrations. However, the great majority of extinctions in Afro-Eurasia and the Americas occurred during the transition from the Pleistocene to the Holocene epoch (13,000 BCE to 8,000 BCE). This extinction wave did not stop at the end of the Pleistocene, continuing, especially on isolated islands, in human-caused extinctions, although there is debate as to whether these should be considered separate events or parts of the same event.

Among the main causes hypothesized by paleontologists are overkill by the widespread appearance of humans and natural climate change. A notable modern human presence first appeared during the Middle Pleistocene in Africa, and started to establish continuous, permanent populations in Eurasia and Australasia from 100,000 BCE and 63,000 BCE respectively, and the Americas from 22,000 BCE.

A variant of the former possibility is the second-order predation hypothesis, which focuses more on the indirect damage caused by overcompetition with nonhuman predators. Recent studies have tended to favor the human-overkill theory.

Extinctions by biogeographic realm

Summary

Introduction

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.

There are three main hypotheses to explain this extinction:
* climate change associated with the advance and retreat of major ice caps or ice sheets.
* "prehistoric overkill hypothesis"
* the extinction of the woolly mammoth allowed the extensive grassland to become birch forest, then subsequent forest fires changed the climate.
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. 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. The later disappearance of these island species correlates with the later colonization of these islands by humans.

Alternative hypotheses to the theory of human responsibility include climate change associated with the last glacial period, and the Younger Dryas impact hypothesis as well as Tollmann's hypothesis that extinctions resulted from bolide impacts.

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.

Afrotropic and Indomalaya: Africa and southern Asia

The Afrotropic and Indomalaya biogeographic realms, or Old World tropics, were relatively spared by the Late Pleistocene extinctions. Sub-Saharan Africa and southern Asia are the only regions that have terrestrial mammals weighing over 1000 kg today. However, there are indications of megafaunal extinction events throughout the Pleistocene, particularly in Africa two million years ago, which coincide with key stages of human evolution and climatic trends. The center of human evolution and expansion, Africa and Asia were inhabited by advanced hominids by 2mya, with ''Homo habilis'' in Africa, and ''Homo erectus'' on both continents. By the advent and proliferation of ''Homo sapiens'' circa 315,000 BCE, dominant species included ''Homo heidelbergensis'' in Africa, the denisovans and neanderthals (fellow ''H. heidelbergensis'' descendants) in Eurasia, and ''Homo erectus'' in Eastern Asia. Ultimately, on both continents, these groups and other populations of Homo were subsumed by successive radiations of ''H. sapiens''. There is evidence of an early migration event 268,000 BCE and later within neanderthal genetics, however the earliest dating for ''H. sapiens'' inhabitation is 118,000 BCE in Arabia, China and Israel, and 71,000 BCE in Indonesia. Additionally, not only have these early Asian migrations left a genetic mark on modern Papuan populations, the oldest known pottery in existence was found in China, dated to 18,000 BCE. Particularly during the late Pleistocene, megafaunal diversity was notably reduced from both these continents, often without being replaced by comparable successor fauna. Climate change has been explored as a prominent cause of extinctions in Southeast Asia.

* Several Bovidae spp.
** Indian aurochs (''Bos'' ''primigenius'' ''namadicus'') (ancestor to the domestic zebu cattle)
** ''Bos palaesondaicus'' (ancestor to the banteng)
** ''Bison hanaizumiensis''
** Cebu tamaraw (''Bubalus cebuensis'')
** ''Bubalus grovesi''
** ''Bubalus wansijocki''
** Short-horned water buffalo (''Bubalus mephistopheles'')
** Giant long-horned buffalo (''Pelorovis'')
** Giant hartebeest (''Megalotragus'')
** ''Rusingoryx''
** Various ''Gazella'' spp.
* ''Sinomegaceros''
* ''Megaceroides algericus''
* '' Dorcabune''
* ''Hippopotamus'' spp.
** Hippopotamus (''Hippopotamus amphibius''; extirpated in western Asia circa 1,000 BCE)
** All Malagasy hippopotamus spp.
*** Malagasy dwarf hippopotamus
*** Malagasy pygmy hippopotamus,
*** ''Hippopotamus laloumena''
* ''Hexaprotodon''
* Wild ''Equus'' spp.
** ''Equus capensis''
** Saharan zebra (''Equus mauritanicus'')
** ''Equus namadicus''
** Indian horse
** Yunnan horse
* Several Rhinoceros (Rhinocerotidae) spp.
** ''Ceratotherium mauritanicum''
** ''Rhinoceros philippinensis''
** South Asian rhinoceros (''Rhinoceros sivalensis'')
* Giant tapir (''Tapirus augustus'')
* Various Felidae spp.
** Sri Lanka lion (''Panthera leo'' ''sinhaleyus'')
** Leopard (''Panthera pardus''; extirpated from Japan and Sumatra)
** Tiger (''Panthera tigris''; extirpated from Japan, Western and Central Asia, Java, Bali, Borneo and Palawan)
* ''Ailuropoda baconi'' (ancestor to the giant panda)
* Aardvark (''Orycteropus afer''; extirpated in South Asia circa 13,000 BCE)
* ''Stegodon''
* Elephas spp.
** ''Elephas hysudricus''
** Blora elephant (''Elephas hysudrindicus'')
** Asian Elephant (extirpated in Java and Syria)
* ''Palaeoloxodon'' spp.
** Asian straight-tusked elephant (largest land mammal on record)
** Naumann's elephant
* ''Loxodonta atlantica'' (possible ancestor of the African bush elephant)
* East Timor giant rat (''Coryphomys'')
* Verhoeven's giant tree rat (''Papagomys theodorverhoeveni'')
* Asian ostrich (''Struthio asiaticus'')
* Japanese flightless duck (''Shiriyanetta hasegawai'')
* Bennu heron (''Ardea bennuides'')
* ''Leptoptilos robustus''
* ''Hipposideros besaoka''
* Giant fossa (''Cryptoprocta spelea'')
* ''Microgale macpheei''
* Bibymalagasy (aardvark-like mammals endemic to Madagascar)
* Giant members of lemur (Lemuroidea)
** Giant aye-aye (''Daubentonia robusta'')
** Giant ruffed lemur (''Pachylemur'')
** Koala lemur (''Megaladapis'')
** All monkey lemur (Archaeolemuridae) spp.
*** ''Hadropithecus''
*** ''Archaeolemur''
** All sloth lemur (Palaeopropithecidae) spp.
*** ''Archaeoindris'' (largest lemur on record)
*** ''Palaeopropithecus''
*** ''Babakotia''
*** ''Mesopropithecus''
* All members of elephant bird, also known as vorompatra in Malagasy language (Aepyornithidae)
** ''Aepyornis''
** ''Mullerornis''
** ''Vorombe titan'' (largest bird on record)
* Malagasy sheldgoose (''Centrornis'')
* Malagasy shelduck (''Alopochen sirabensis'')
* Hova gallinule (''Hovacrex roberti'')
* Malagasy lapwing (''Vanellus madagascariensis'')
* Malagasy crowned eagle (''Stephanoaetus maher'')
* Ampoza ground roller (''Brachypteracias langrandi'')
* ''Voay''
* Various ''Aldabrachelys'' giant tortoise
** '' Abrupt giant tortoise''
** '' Grandidier's giant tortoise''
* ''Canariomys''
** Tenerife giant rat (''Canariomys bravoi'')
** Gran Canaria giant rat (''Canariomys tamarani'')
* Canary Islands quail (''Coturnix gomerae'')
* Long-legged bunting (''Emberiza alcoveri'')
* ''Centrochelys''
* ''Gallotia goliath''
* Several monkey (Simiiformes) spp.
** Vietnamese Orangutan
** Various ''Homo'' spp.
*** Archaic African hominins (undescribed)
*** ''Homo erectus''
*** Flores Man
*** ''Homo luzonensis''
*** Denisovans (''Homo'' sp.)
*** Neanderthals (''Homo'' (''sapiens'') ''neanderthalensis'')
*** Red Deer Cave people (''Homo sapiens'')
*** Unknown Asiatic hominins (''Homo'' sp.)
*** Balangoda Man (''Homo sapiens balangodensis'')

Palearctic: Europe and northern Asia

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 swampy wetlands, 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. 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.

Europe and northern Asia, being far colder and drier than today, was largely hegemonized by the mammoth steppe, an ecosystem dominated by palatable high-productivity grasses, herbs and willow shrubs. This supported an extensive biota of grassland fauna and stretched eastwards from Spain in the Iberian Peninsula to Yukon in modern-day Canada. The area was populated by many species of grazers which assembled in large herds similar in size to those in Africa today. Populous species which roamed the great grasslands included the woolly mammoth, woolly rhinoceros, ''Elasmotherium'', steppe bison, Pleistocene horse, muskox, ''Cervalces'', reindeer, various antelopes ( goat-horned antelope, mongolian gazelle, saiga antelope and twisted-horned antelope) and steppe pika. Carnivores included Eurasian cave lion, scimitar cat, cave hyena, grey wolf, dhole and the Arctic fox.

At the edges of these large stretches of grassland could be found more shrub-like terrain and dry conifer forest and woodland (akin to forest steppe or taiga). The browsing collective of megafauna included woolly rhinoceros, giant deer, moose, ''Cervalces'', tarpan, aurochs, woodland bison, camels and smaller deer (Siberian roe deer, red deer and Siberian musk deer). Brown bears, wolverines, cave bear, wolves, lynx, leopards and red foxes also inhabited this biome. Tigers were at stages also present, from the edges of eastern Europe around the Black Sea to Beringia. The more Montane ecosystems, mountainous terrain, incorporating Montane grasslands and shrublands, montane grassland, Subalpine zone, subalpine conifer forest, alpine tundra and Schrofen, broken, craggy slopes, was occupied by several species of mountain-going animals like argali, chamois, Capra (genus), ibex, mouflon, Red panda, pika, wolves, leopards, Ursus (genus), ''Ursus spp.'' and lynx, with snow leopards, Baikal yak and snow sheep in northern Asia. Arctic tundra, which lined the north of the mammoth steppe, reflected modern ecology with species such as the polar bear, Tundra wolf, wolf, reindeer and muskox.

Other biomes, although less noted, were significant in contributing to the diversity of fauna in Late Pleistocene Europe. Warmer grasslands such as Temperate grasslands, savannas, and shrublands, temperate steppe and Mediterranean forests, woodlands, and scrub, Mediterranean savannah hosted ''Stephanorhinus'', gazelle, European bison, Asian ostriches, ''Leptobos'', cheetah and onager. These biomes also contained an assortment of mammoth steppe fauna, such as saiga antelope, History of lions in Europe, lions, scimitar cats, cave hyenas, wolves, Pleistocene horse, steppe bison, twisted-horned antelope, aurochs and camels. Temperate coniferous forest, Temperate coniferous, Temperate deciduous forest, deciduous, Temperate broadleaf and mixed forest, mixed broadleaf and Mediterranean forests, woodlands, and scrub, Mediterranean forest and open woodland accommodated straight-tusked elephants, ''Praemegaceros'', ''Stephanorhinus'', wild boar, bovids such as European bison, tahr and West Caucasian tur, tur, species of ''Ursus (genus), Ursus'' such as the Ursus etruscus, Etruscan bear and smaller deer (Roe deer, red deer, fallow deer and Mediterranean deer) with several mammoth steppe species such as lynx, tarpan, wolves, dholes, moose, giant deer, woodland bison, leopards and aurochs. Woolly rhinoceros and Woolly mammoth, mammoth occasionally resided in these temperate biomes, mixing with predominately temperate fauna to escape harsh glacials. In warmer wetlands, Bubalus murrensis, European water buffalo and Hippopotamus antiquus, hippopotamus were present. Although these habitats were restricted to Refugium (population biology), micro refugia and to southern Europe and its fringes, being in Iberian Peninsula, Iberia, Italy, the Balkans, Geography of Ukraine, Ukraine's Black Sea Pontic–Caspian steppe, basin, the Caucasus and western Asia, during inter-glacials these biomes had a far more northernly range. For example, hippopotamus inhabited Great Britain and straight-tusked elephant the The Netherlands, Netherlands, as recently as 80,000 BCE and 42,000 BCE respectively.

The first possible indications of habitation by hominins are the 7.2 million year old finds of ''Graecopithecus'', 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#Descendants and synonyms, Homo erectus''. Prominent co-current and subsequent species include ''Homo antecessor'', ''Homo cepranensis'', ''Homo heidelbergensis'', neanderthals and denisovans, 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.

Europe's Late Pleistocene biota went through two phases of extinction. Some fauna became extinct before 13,000 BCE, in staggered intervals, particularly between 50,000 BCE and 30,000 BCE. Species include cave bear, ''Elasmotherium'', straight-tusked elephant, ''Stephanorhinus'', Bubalus murrensis, water buffalo, neanderthals, gazelle and scimitar cat. However, the great majority of species were Biodiversity loss, extinguished, extirpated or experienced severe Population bottleneck, population contractions between 13,000 BCE and 9,000 BCE, ending with the Younger Dryas. At that time there were small ice sheets in Scotland and Scandinavia. The mammoth steppe Ecological collapse, disappeared from the vast majority of its former range, either due to a permanent shift in Ecological succession, climatic conditions, or an absence of Ecosystem engineer, ecosystem management due to Ecological extinction, decimated, Population fragmentation, fragmented or Biodiversity loss, extinct populations of Megafauna, megaherbivores. This led to a Ecological threshold, region wide Extinction debt, extinction extinction vortex, vortex, resulting in Density dependence, cyclically Carrying capacity, diminishing Productivity (ecology), bio-productivity and defaunation. Foster's rule, Insular species on List of islands in the Mediterranean, Mediterranean islands such as Sardinia, Sicily, Malta, Cyprus and Crete, went extinct around the same time as humans colonised those islands. Fauna included dwarf Dwarf elephant, elephants, Praemegaceros, megacerines and Hippopotamus (genus), hippopotamuses, and giant Cretan owl, avians, Megalenhydris, otters and Leithia, rodents.

* Various Bovidae spp.
**Steppe bison (''Bison priscus'')
** Baikal yak (''Bos baikalensis'')
** Bubalus murrensis, European water buffalo (''Bubalus murrensis'')
** Tahr, European tahr (''Hemitragus cedrensis'')
** Praeovibos priscus, Giant muskox (''Praeovibos priscus'')
** Myotragus, Balearic Islands cave goat (''Myotragus balearicus'')
** Northern saiga antelope (''Saiga borealis'')
** Twisted-horned antelope (''Spirocerus kiakhtensis'')
** Goat-horned antelope (''Parabubalis capricornis'')
** ''Gazella'' spp.
* Various deer (Cervidae) spp.
** Cervalces latifrons, Broad-fronted moose (''Cervalces latifrons'')
** Giant deer (''Megaloceros giganteus'')
** ''Praemegaceros''
** Candiacervus, Cretan dwarf megacerine (''Candiacervus'')
** Mediterranean deer (''Haploidoceros mediterraneus'')
** Cervus elaphus acoronatus, Palmated red deer (''Cervus elaphus acoronatus'')
* All native ''Hippopotamus (genus), Hippopotamus'' spp.
** Hippopotamus antiquus, European hippopotamus (''Hippopotamus antiquus'')
** Hippopotamus melitensis, Maltese dwarf hippopotamus (''Hippopotamus melitensis'')
** Cyprus dwarf hippopotamus (''Hippopotamus minor'')
** Hippopotamus pentlandi, Sicilian dwarf hippopotamus (''Hippopotamus pentlandi'')
* ''Camelus knoblochi'' and other ''Camelus'' spp.
* Various ''Equus'' spp. e.g.
** Wild horse (Wild horse#Subspecies and their history, ''Equus ferus'' ssp.)
** ''Equus'' Open nomenclature, cf. ''gallicus''
** European ass, European Ass (''Equus hydruntinus'')
** ''Equus'' Open nomenclature, cf. ''latipes''
** ''Equus'' Open nomenclature, cf. ''lenensis''
** ''Equus'' Open nomenclature, cf. ''uralensis''
* All native Rhinocerotidae, Rhinoceros (Rhinocerotidae) spp.
** ''Elasmotherium''
** Woolly rhinoceros (''Coelodonta antiquitatis'')
** ''Stephanorhinus'' spp.
*** Stephanorhinus kirchbergensis, Merck's rhinoceros (''Stephanorhinus kirchbergensis'')
*** Narrow-nosed rhinoceros (''Stephanorhinus hemiotoechus'')
* Cave wolf (''Canis lupus spelaeus'')
*Dire wolf (''Aenocyon dirus'')
* Various Felidae spp.
** Scimitar cat, Eurasian scimitar cat (''Homotherium latidens'')
** Cave lynx (''Lynx pardinus spelaeus'')
** Issoire lynx (''Lynx issiodorensis'')
** Panthera spp.
*** Panthera leo spelaea, Cave lion (''Panthera spelaea'')
*** European ice age leopard (''Panthera pardus spelaea'')
* Cave hyena (''Crocuta crocuta spelaea'')
* European dhole (''Cuon alpinus europaeus'')
* Sardinian dhole (''Cynotherium sardous'')
* Several Lutrinae, otter (Lutrinae) spp.
** Cyrnaonyx, Robust Pleistocene European otter (''Cyrnaonyx'')
** Algarolutra, Pleistocene Mediterranean otter (''Algarolutra'')
** Megalenhydris barbaricina, Sardinian giant otter (''Megalenhydris barbaricina'')
** Sardolutra, Sardinian dwarf otter (''Sardolutra'')
** Cretan otter (''Lutrogale cretensis'')
* Various Ursus (genus), ''Ursus'' spp.
** Steppe brown bear (''Ursus arctos'' "''priscus''")
** Ursus ingressus, Gamssulzen cave bear (''Ursus ingressus'')
** Ursus rossicus, Pleistocene small cave bear (''Ursus rossicus'')
** Cave bear (''Ursus spelaeus'')
** Ursus maritimus tyrannus, Giant polar bear (''Ursus maritimus tyrannus'')
* All native Elephantidae, Elephant (Elephantidae) spp.
** Woolly mammoth (''Mammuthus primigenius'')
** Dwarf elephant, Dwarf mammoth
*** Mammuthus creticus, Cretan dwarf mammoth (''Mammuthus creticus'')
*** Mammuthus lamarmorai, Dwarf Sardinian mammoth (''Mammuthus lamarmorai'')
** Straight-tusked elephant (''Palaeoloxodon antiquus'')
** Dwarf elephant
*** ''Palaeoloxodon chaniensis''
*** Cyprus dwarf elephant (''Palaeoloxodon cypriotes'')
*** Palaeoloxodon falconeri, Pygmy elephant (''Palaeoloxodon falconeri'')
*** ''Palaeoloxodon mnaidriensis''
* Balearic giant dormouse (''Hypnomys'') spp. e.g.
** Majorcan giant dormouse (''Hypnomys morpheus'')
* ''Leithia'' spp. (Maltese and Sicilian giant dormouse)
* Pika (''Ochotona'') spp. e.g.
** Giant pika (''Ochotona whartoni'')
* Asian ostrich (''Struthio asiaticus'')
* Cygnus falconeri, Giant swan (''Cygnus falconeri'')
* Anser djuktaiensis, Yakutian goose (''Anser djuktaiensis'')
* Various European crane (bird), crane spp. (Genus ''Grus (genus), Grus'')
** ''Grus primigenia''
** ''Grus melitensis''
* Cretan owl (''Athene cretensis'')
* Denisovans (''Homo'' sp.)
* 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-
* †European lion (''Panthera leo europaea)''
* Tiger (''Panthera tigris'', from the Ukraine, Ukrainian Black Sea to Beringia)
* Cheetah (''Acinonyx'' ''jubatus'')
* Leopard (''Panthera pardus)''
* Snow leopard (''Panthera uncia'')
* Eurasian lynx, Eurasian and Iberian lynx, Iberian lynx (Eurasian lynx, ''Lynx lynx'' and Iberian lynx, ''Lynx pardinus'')
* Wolverine (''Gulo gulo'')
* Polar bear (''Ursus maritimus'')
* Arctic fox (''Vulpes lagopus'')
* Dhole (''Cuon alpinus)''
* Gray wolf (†Megafaunal wolf, Megafaunal et Beringian wolf, and the Paleolithic dog (''Gray wolf, Canis lupus''))
* †Tarpan (''Equus ferus ferus'')
* Fallow deer (''Dama dama'')
* Mouflon (''Ovis gmelini)''
* Chamois (''Rupicapra'' spp.)
* West Caucasian tur (''Capra caucasica'')
* Saiga antelope (''Saiga tatarica'')
* Reindeer (''Rangifer tarandus'')
* Moose (''Alces alces'')
* Onager ''(Equus hemionus'')
* †Aurochs (''Bos primigenius'')
* European bison (''Bison bonasus'')
* Wild water buffalo, Asian water buffalo (''Bubalus arnee'')
* Musk ox (''Ovibos moschatus)''
* Asian elephant (''Elephas maximus,'' from the Black Sea to North China, Northern China)
* Steppe pika (''Ochotona pusilla'')
* Great jerboa (''Allactaga major'')
* Hippopotamus (''Hippopotamus amphibius'')
* Northern bald ibis (''Geronticus eremita)''
* †Great auk (''Pinguinus impennis'')
* Snowy owl (''Bubo scandiacus'')
* Barbary macaque (''Macaca sylvanus'')

Nearctic:

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 . 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. 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. 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. Human habitation commenced unequivocally approximately 22,000 BCE north of the glacier, and 13,500 BCE south, however disputed evidence of southern human habitation exists from 130,000 BCE and 17,000 BCE onwards, described from sites in California and Meadowcroft Rockshelter, Meadowcroft in Pennsylvania. Other prominent paleontological sites documenting human expansion into North America can be found in Mexico and Panama, the crossroads of the Great American Interchange, American Interchange.

North American extinctions (noted as herbivores (H) or carnivores (C)) included:
* Various Bovidae spp.
** Most forms of Pleistocene bison (only American bison, ''Bison bison'' in North America, and European bison, ''Bison bonasus'' in Eurasia, survived)
***Bison antiquus, Ancient bison (''Bison antiquus'') (H)
*** Bison latifrons, Long-horned/Giant bison (''Bison latifrons'') (H)
*** Steppe bison (''Bison priscus'') (H)
*** ''Bison occidentalis'' (H)
** Wild yak (''Bos mutus''; extirpated) (H)
** Several members of ''Caprinae'' (the muskox survived)
*** Praeovibos priscus, Giant muskox (''Praeovibos priscus'') (H)
*** Shrub-ox (''Euceratherium collinum'') (H)
*** Harlan's muskox (''Bootherium bombifrons'') (H)
*** Soergelia mayfieldi, Soergel's ox (''Soergelia mayfieldi'') (H)
*** Harrington's mountain goat (''Oreamnos harringtoni''; smaller and more southern distribution than its Mountain Goat, surviving relative) (H)
** Saiga, Saiga antelope (''Saiga tatarica''; extirpated) (H)
* Stag-moose (''Cervalces scotti'') (H)
* American mountain deer (''Odocoileus lucasi'') (H)
* ''Torontoceros, Torontoceros hypnogeos'' (H)
* Various Antilocapridae genera (pronghorns survived)
** Capromeryx minor, ''Capromeryx'' (H)
** ''Stockoceros'' (H)
** ''Tetrameryx'' (H)
** Antilocapra pacifica, Pacific pronghorn (''Antilocapra pacifica'') (H)
* Several peccary (Tayassuidae) spp.
**Platygonus compressus, Flat-headed peccary (''Platygonus'') (H)
** Long-nosed peccary (''Mylohyus'') (H)
**Collared peccary (''Dicotyles tajacu''; extirpated, range semi-recolonised) (H) (''Muknalia minimus'' is a junior synonym)
* Various members of Camelidae
** Camelops, Western camel (''Camelops hesternus'') (H)
** Hemiauchenia, Stilt legged llamas (''Hemiauchenia'' ssp.) (H)
** Palaeolama, Stout legged llamas (''Palaeolama'' ssp.) (H)
* All native forms of Equidae
** ''Equus alaskae'' (H)
** ''Equus cedralensis'' (H)
** Equus conversidens, Mexican horse (''Equus conversidens'') (H)
** ''Equus complicatus'' (H)
** ''Equus fraternus'' (H)
** Equus giganteus, Giant horse (H)
** Onager (''Equus hemionus''; extirpated) (H)
** Kiang (''Equus kiang''; extirpated) (H)
** Equus lambei, Yukon horse (''Equus lambei'') (H)
** ''Equus mexicanus'' (H)
** Equus niobrarensis, Niobrara horse (''Equus niobrarensis'') (H)
** Equus pacificus, Pacific horse (''Equus pacificus'') (H)
** Equus occidentalis, Western horse (''Equus occidentalis'') (H)
** ''Equus semiplicatus'' (H)
** Hagerman horse (''Equus simplicidens'') (H)
** Equus scotti, Scott's horse (''Equus scotti'') (H)
** Haringtonhippus, Stilt-legged horse (''Haringtonhippus francisci'' / ''Equus francisci''; may be a synonym of Mexican horse) (H)
* All members of North American tapir (''Tapirus''; four species)
** California tapir (''Tapirus californicus'') (H)
** Tapirus merriami, Merriam's tapir (''Tapirus merriami'') (H)
** Tapirus veroensis, Vero tapir (''Tapirus veroensis'') (H)
* ''Mixotoxodon'' (H)
* An indeterminate Litopterna, litoptern from Mexico City, México City.
* Several Felidae spp.
** Smilodon, North American saber-toothed cat (''Smilodon fatalis'') (C)
** Homotherium, North American scimitar cat (''Homotherium serum'') (C)
** American cheetah (''Miracinonyx''; not true cheetah)
*** ''Miracinonyx inexpectatus'' (C)
*** ''Miracinonyx trumani'' (C)
** Cougar (''Puma concolor''; megafaunal Ecomorphology, ecomorph extirpated from North America, South American populations recolonised former range) (C)
** Jaguarundi (''Herpailurus yagouaroundi''; extirpated, range semi-recolonised) (C)
** Margay (''Leopardus weidii''; extirpated) (C)
** Ocelot (''Leopardus pardalis''; extirpated, range marginally recolonised) (C)
** Eurasian lynx (''Lynx lynx''; extirpated) (C)
** Panthera onca augusta, Pleistocene North American jaguar (''Panthera onca augusta''; range semi-recolonised by other subspecies) (C)
** American lion (''Panthera atrox''; endemic to North America after 340,000 BP) (C)
** Panthera spelaea, Eurasian cave lion (''Panthera spelaea''; present only as far as modern day Yukon) (C)
*Steppe polecat (''Mustela eversmanii''; extirpated) (C)
*Dire wolf (''Aenocyon dirus'') (C)
*Pleistocene coyote (''Canis latrans orcutti'') (C)
* Megafaunal wolf e.g.
** Beringian wolf (''Canis lupus'' ssp.) (C)
*Dhole (''Cuon alpinus''; extirpated) (C)
* ''Protocyon troglodytes'' (C)
*Brachyprotoma obtusata, Short-faced skunk (''Brachyprotoma obtusata'') (C)
* Various bear (Ursidae) spp.
** Giant short-faced bear, Arctodus simus'' (C)''
** Florida cave bear, Florida spectacled bear (''Tremarctos floridanus'') (C)
** Arctotherium, South American short-faced bear (''Arctotherium wingei'') (C)
** Ursus maritimus tyrannus, Giant polar bear (''Ursus maritimus tyrannus''; a possible inhabitant) (C)
* Pristine mustached bat (''Pteronotus'' (''Phyllodia'') ''pristinus'') (C)
* Stock's vampire bat (''Desmodus stocki'') (C)
* All native spp. of Proboscidea
** American mastodon (''Mammut americanum'') (H)
** Mammut pacificus, Pacific mastodon (''Mammut pacificus'') (H)
** Gomphotheriidae spp.
*** ''Cuvieronius'' (H)
*** ''Stegomastodon'' (H)
** Mammoth (''Mammuthus'') spp.
*** Columbian mammoth (''Mammuthus columbi'') (H)
*** Pygmy mammoth (''Mammuthus exilis'') (H)
*** Woolly mammoth (''Mammuthus primigenius'') (H)
* Steller's sea cow (''Hydrodamalis gigas''; extirpated in North America) (H)
* Castoroides, Giant beaver (''Castoroides'') spp.
** ''Castoroides, Castoroides ohioensis'' (H)
** ''Castoroides, Castoroides leiseyorum'' (H)
* ''Neochoerus'' spp. e.g.
** Neochoerus pinckneyi, Pinckney's capybara (''Neochoerus pinckneyi'') (H)
* Klein's porcupine (''Erethizon kleini'') (H)
* All giant hutia (Heptaxodontidae) spp.
** Blunt-toothed giant hutia (''Amblyrhiza inundata''; could grow as large as an American black bear) (H)
** Plate-toothed giant hutia (''Elasmodontomys obliquus'') (H)
** Twisted-toothed mouse (''Quemisia gravis'') (H)
** Osborn's key mouse (''Clidomys osborn's'') (H)
** ''Xaymaca fulvopulvis'' (H)
* Aztlanolagus, Aztlan rabbit (''Aztlanolagus'' sp.) (H)
* Webb's marsh rabbit (''Sylvilagus webbi'') (H)
* Giant pika (''Ochotona whartoni'') (H)
* All members of the Xenotrichini, Antilles monkeys (''Xenotrichini'')
** Jamaican monkey (''Xenothrix mcgregori'') (H)
** Cuban monkey (''Paralouatta'') (H)
** Hispaniola monkey (''Antillothrix bernensis'') (H)
** ''Insulacebus toussaintiana'' (H)
* Giant anteater (''Myrmecophaga tridactyla''; extirpated, range partially recolonised) (C)
* All remaining ground sloth spp.
** ''Eremotherium'' (Megatheriidae, megatheriid ground sloth) (H)
** ''Nothrotheriops'' (Nothrotheriidae, nothrotheriid ground sloth) (H)
** Megalonychidae, Megalonychid ground sloth spp.
*** ''Megalonyx'' (H)
*** ''Nohochichak'' (H)
*** ''Xibalbaonyx'' (H)
** Megalocnidae, Megalocnid Pilosans of the Caribbean, Greater Antillean dwarf ground sloth spp. (some were probably at least partly arboreal)
*** ''Acratocnus'' (H)
*** ''Habanocnus'' (H)
*** ''Megalocnus'' (H)
*** ''Miocnus'' (H)
*** ''Neocnus'' (H)
** Mylodontidae, Mylodontid ground sloth spp.
*** ''Paramylodon'' (H)
*** ''Glossotherium'' (H)
* All members of Glyptodontidae
** ''Glyptotherium'' (H)
** ''Pachyarmatherium'' (H)
* Dasypus bellus, Beautiful armadillo (''Dasypus bellus'') (H)
* All Pampatheriidae spp. e.g.
** ''Holmesina'' (H)
** ''Pampatherium'' (H)
* Bermuda flightless duck (''Anas pachyscelus'') (H)
* Chendytes, Californian flightless sea duck (''Chendytes lawi'') (C)
* Stiff-tailed duck, Mexican stiff-tailed duck (''Oxyura zapatima'') (H)
* Turkey (bird), Turkey (''Meleagris'') spp.
** Californian turkey (''Meleagris californica'') (H)
** ''Meleagris crassipes'' (H)
* Various Gruiformes spp.
** All Nesotrochis, cave rail (''Nesotrochis'') spp. e.g.
*** Antillean cave rail (''Nesotrochis debooyi'') (C)
** Barbados rail (Incertae sedis) (C)
** Cuban flightless crane (''Antigone cubensis'') (H)
** Grus pagei, La Brea crane (''Grus pagei'') (H)
* Various flamingo (Phoenicopteridae) spp.
** Minute flamingo (''Phoenicopterus minutus'') (C)
** Cope's flamingo (''Phoenicopterus copei'') (C)
* Dow's puffin (''Fratercula dowi'') (C)
* Pleistocene Mexican Loon, diver spp.
**''Plyolimbus baryosteus'' (C)
** ''Podiceps'' spp.
***''Podiceps parvus'' (C)
* Ciconia maltha, La Brea/Asphalt stork (''Ciconia maltha'') (C)
* Wetmore's stork (''Mycteria wetmorei'') (C)
* Pleistocene Mexican cormorants spp. (genus ''Phalacrocorax'')
**''Phalacrocorax goletensis'' (C)
** ''Phalacrocorax chapalensis'' (C)
* Jamaican ibis (''Xenicibis xympithecus'') (C)
* All remaining Teratornithidae, teratorn (Teratornithidae) spp.
**Aiolornis, ''Aiolornis incredibilis'' (C)
** Cathartornis, ''Cathartornis gracilis'' (C)
** Oscaravis, ''Oscaravis olsoni'' (C)
** Teratornis, ''Teratornis merriami'' (C)
** Teratornis, ''Teratornis woodburnensis'' (C)
* Several New World vultures (Cathartidae) spp.
** Black vulture, Pleistocene black vulture (''Coragyps occidentalis'' ssp.) (C)
** Gymnogyps amplus, Megafaunal Californian condor (''Gymnogyps amplus'') (C)
** Breagyps clarki, Clark's condor (''Breagyps clarki'') (C)
** Gymnogyps varonai, Cuban condor (''Gymnogyps varonai'') (C)
* Several Accipitridae spp.
** Neophrontops americanus, American neophrone vulture (''Neophrontops americanus'') (C)
** Woodward's eagle (''Amplibuteo woodwardi'') (C)
** Buteogallus borrasi, Cuban great hawk (''Buteogallus borrasi'') (C)
** Buteogallus daggetti, Daggett's eagle (''Buteogallus daggetti'') (C)
** Buteogallus fragilis, Fragile eagle (''Buteogallus fragilis'') (C)
** Gigantohierax suarezi, Cuban giant hawk (''Gigantohierax suarezi'') (C)
** Neogyps errans, Errant eagle (''Neogyps errans'') (C)
** Spizaetus grinnelli, Grinnell's crested eagle (''Spizaetus grinnelli'') (C)
** Spizaetus willetti, Willett's hawk-eagle (''Spizaetus willetti'') (C)
** Titanohierax, Caribbean titan hawk (''Titanohierax'') (C)
* Several owl (Strigiformes) spp.
** Asphaltoglaux, Brea miniature owl (''Asphaltoglaux'') (C)
** Glaucidium kurochkini, Kurochkin's pygmy owl (''Glaucidium kurochkini'') (C)
** Oraristrix, Brea owl (''Oraristix brea'') (C)
** Ornimegalonyx, Cuban giant owl (''Ornimegalonyx'') (C)
* Bermuda flicker (''Colaptes oceanicus'') (C)
* Several Caracara (subfamily), caracara (Caracarinae) spp.
** Bahaman terrestrial caracara (''Caracara (genus), Caracara'' sp.) (C)
** Puerto Rican terrestrial caracara (''Caracara (genus), Caracara'' sp.) (C)
** Jamaican caracara (''Carcara tellustris'') (C)
** Cuban caracara (''Milvago'' sp.) (C)
** Hispaniolan caracara (''Milvago'' sp.) (C)
* Saint Croix macaw (''Ara autocthones'') (H)
* Rhynchopsitta phillipsi, Mexican thick-billed parrot (''Rhynchopsitta phillipsi'') (H)
* Puerto Rican crow (''Corvus pumilis'') (C)
* Several giant tortoise spp.
** ''Hesperotestudo'' (H)
** ''Gopherus'' spp.
*** ''Gopherus donlaloi'' (H)
** ''Chelonoidis'' spp.
*** ''Chelonoidis marcanoi'' (H)
*** ''Chelonoidis alburyorum'' (H)

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, Elk, 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. 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. Because ancient bison evolved into living bison, 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 culture, Clovis people (''q.v.''), who were thought to use Atlatl, 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.

Neotropic: South America

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 (biology), family. Those that survived the interchange included the ground sloths, glyptodonts, litopterns, pampatheres, Phorusrhacidae, phorusrhacids (terror birds) and notoungulates; all managed to extend their range to North America. 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, and the colder, arid interior resulted in the advance of temperate lowland woodland, tropical savanna and desert at the expense of rainforest. Within these open environments, megafauna diversity was extremely dense, with over 40 genera recorded from the Guerrero member of Luján, Buenos Aires, Luján Formation alone. Ultimately, by the Holocene, mid-Holocene, all the preeminent genera of megafauna became extinct- the last specimens of ''Doedicurus'' and ''Toxodon'' have been dated to 5th millennium BC, 4,555 BCE and 30th century BC, 3,000 BCE respectively. Their smaller relatives remain, including anteaters, Sloth, tree sloths, armadillos; Ameridelphia, New World marsupials: opossums, shrew opossums, and the monito del monte (actually more related to Australidelphia, Australian marsupials). Intense human habitation was established circa 11,000 BCE, however partly disputed evidence of Pre-Clovis, 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. 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 Peccary, peccaries, marsh deer (''Capreolinae''), giant anteaters, spectacled bears, Maned wolf, maned wolves, Cougar, pumas, ocelots, jaguars, Rhea (bird), rheas, emerald tree boas, boa constrictors, anacondas, American crocodiles, Caimaninae, caimans, and giant rodents such as capybaras.

* Several Cervidae spp.
** ''Morenelaphus''
** ''Antifer''
** ''Agalmaceros blicki''
** ''Odocoileus salinae''
* Various Camelidae spp.
** ''Eulamaops''
** Stilt legged llama ''Hemiauchenia''
** Stout legged llama ''Palaeolama''
* All Pleistocene wild horse genera (Equidae)
** ''Equus'' (''Amerhippus'')
*** ''Equus andium''
*** ''Equus insulatus''
*** ''Equus neogeus''
** ''Hippidion'' (''Onohippidium'')
*** ''Hippidion devillei''
*** ''Hippidion principale''
*** ''Hippidion saldiasi''
* All remaining Meridiungulata genera
** Litopterna spp.
*** ''Macrauchenia''
*** ''Macraucheniopsis''
*** Proterotheriidae spp. e.g.
**** (''Neolicaphrium, Neolicaphrium recens'')
*** ''Xenorhinotherium''
** Notoungulata spp.
*** ''Hegetotheriidae spp.''
*** ''Mesotheriidae spp.''
*** ''Mixotoxodon''
*** ''Toxodon''
* Several Felidae spp.
** Saber-toothed cat (''Smilodon'') spp.
*** Smilodon fatalis, North American saber-toothed cat (''Smilodon fatalis'')
*** Smilodon populator, South American saber-toothed cat (''Smilodon populator'')
** Pleistocene South American jaguar (''Panthera onca mesembrina'')
* Dire wolf (''Dire wolf, Aenocyon dirus'')
* Nehring's wolf (''Canis nehringi'')
* ''Protocyon'' spp.
** ''Protocyon trogolodytes''
** ''Protocyon tarijense''
* ''Dusicyon avus''
* Pleistocene bush dog (''Speothos pacivorus'')
* South American short-faced bear (''Arctotherium'' spp.)
** ''Arctotherium bonairense''
** ''Arctotherium tarijense''
** ''Arctotherium wingei''
* Giant vampire bat (''Desmodus draculae'')
* All remaining Gomphotheridae spp.
** ''Cuvieronius''
** ''Notiomastodon, Notiomastodon/Haplomastodon''
* ''Neochoerus''
* All remaining ground sloth genera
** Megatheriidae spp.
*** ''Eremotherium''
*** Megatherium, Giant ground sloth
** Nothrotheriidae spp.
*** ''Nothropus''
*** ''Nothrotherium''
** Megalonychidae spp.
*** ''Ahytherium''
*** ''Australonyx''
*** ''Diabolotherium''
*** ''Megistonyx''
*** ''Proplatyarthrus''
*** ''Valgipes''
** Mylodontidae spp.
*** ''Catonyx''
*** ''Glossotherium''
*** ''Lestodon''
*** ''Mylodon''
*** ''Nematherium''
*** ''Octomylodon''
*** ''Orophodon''
*** ''Scelidotherium''
*** ''Scelidodon''
* All remaining Glyptodontinae spp.
** ''Doedicurus''
** ''Eleutherocercus''
** ''Glyptodon, Glyptodon/Chlamydotherium''
** ''Heteroglyptodon''
** ''Hoplophorus''
** ''Lomaphorus''
** ''Neosclerocalyptus''
** ''Neuryurus''
** ''Panochthus''
** ''Parapanochthus''
** ''Plaxhaplous''
** ''Sclerocalyptus''
* Several Dasypodidae spp.
** Beautiful armadillo (''Dasypus bellus'')
** ''Eutatus''
** ''Pachyarmatherium''
** ''Propaopus''
* All Pampatheriidae spp.
** ''Holmesina'' (et ''Chlamytherium occidentale'')
** ''Pampatherium''
** ''Tonnicinctus''
* ''Psilopterus'' (small terror bird remains dated to the Late Pleistocene, but these are disputed)
* Various Caracarinae spp.
** Venezuelan caracara (''Caracara major'')
** Seymour's caracara (''Caracara seymouri'')
** Peruvian caracara (''Milvago brodkorbi'')
* Various ''Cathartidae spp.''
** ''Pampagyps imperator''
** ''Geronogyps reliquus''
** ''Wingegyps cartellei''
** ''Pleistovultur nevesi''
* ''Caiman venezuelensis''
* ''Chelonoidis lutzae'' (Argentina)

The Pacific (Australasia and Oceania)

There exists two hypotheses regarding the extinction of the Australalasian 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.  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.  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.  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.  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.   

In Australia (continent), Sahul (a former continent composed of Fauna of Australia, Australia and Fauna of New Guinea, New Guinea), the sudden and extensive spate of extinctions occurred earlier than in the rest of the world. Most evidence points to a 20,000 year period after human arrival circa 63,000 BCE, but scientific argument continues as to the exact date range. In the rest of the Pacific (other Australasian realm, Australasian islands such as New Caledonia, and Oceanian realm, 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.

The extinctions in the Pacific included:
* Various members of ''Diprotodontidae''
** ''Diprotodon''
** ''Euowenia''
** ''Euryzygoma dunense''
** ''Hulitherium tomasetti''
** ''Maokopia ronaldi''
** ''Nototherium''
** ''Zygomaturus''
* ''Palorchestes'' ("marsupial tapir")
* Various members of ''Wombat, Vombatidae''
** ''Lasiorhinus angustidens'' (giant wombat)
** ''Phascolomys'' (giant wombat)
** ''Phascolonus'' (giant wombat)
** ''Ramasayia magna'' (giant wombat)
** ''Vombatus hacketti'' (Hackett's wombat)
** ''Warendja wakefieldi'' (dwarf wombat)
* ''Giant koala, Phascolarctos stirtoni'' (giant koala)
* Marsupial lion (''Thylacoleo carnifex)''
* Various members of ''Macropodidae''
** ''Procoptodon'' (short-faced kangaroos) e.g.
*** ''Procoptodon goliah''
** ''Sthenurus'' (giant kangaroo)
** ''Simosthenurus'' (giant kangaroo)
** Various ''Macropus'' (giant kangaroo) spp. e.g.
*** ''Macropus titan''
*** ''Macropus pearsoni''
** ''Protemnodon'' (giant wallaby)
** ''Troposodon'' (wallaby)
** ''Bohra (genus), Bohra'' (giant tree kangaroo)
** ''Propleopus, Propleopus oscillans'' (omnivorous, giant musky rat-kangaroo)
* Thylacine (''Thylacinus cynocephalus''; extirpated on mainland Australia and New Guinea)
* Various forms of ''Sarcophilus'' (Tasmanian devil)
**''Sarcophilus laniarius'' (25% larger than modern species)
** ''Sarcophilus moornaensis''
** ''Sarcophilus harrisii'' (extirpated on mainland Australia)
* ''Murrayglossus hacketti'' (giant echidna)
* ''Megalibgwilia'' (oldest known echidna, same extinction period)
* Pygmy Cassowary (''Casuarius lydekkeri'')
* Genyornis, Mihirung (a Dromornithidae, dromornithid
* Tasmanian nativehen (''Tribonyx mortierii''; extirpated on mainland Australia)
* Giant malleefowl (''Leipoa gallinacea'')
* Several Phoenicopteridae spp.
** American flamingo (''Phoenicopterus ruber''; extirpated in Australia)
** ''Xenorhynchopsis'' spp. (Australian flamingo)
*** ''Xenorhynchopsis minor''
*** ''Xenorhynchopsis tibialis''
** ''Ocyplanus proeses'' (Australian flamingo)
*''Ikanogavialis'' (the last fully marine crocodilian)
* ''Pallimnarchus'' (Australian freshwater crocodile)
* ''Quinkana'' (Australian terrestrial crocodile, apex predator)
* ''Wonambi'' (a five-to-six-metre-long Australian constrictor snake)
* Megalania (''Varanus pricus'') (a giant predatory monitor lizard)
* Several spp. of Meiolaniidae (giant armoured tortoises)
** ''Meiolania''
** ''Ninjemys''
* ''Sylviornis'' (giant, flightless New Caledonian Galliformes, galliform; largest in existence)
* Noble megapode (''Megavitornis altirostris'')
* Giant ''Megapodius'' spp.
** Pile-builder megapode (''Megapodius molistructor'')
** Consumed scrubfowl (''Megapodius alimentum'')
** Viti Levu scrubfowl (''Megapodius amissus'')
* New Caledonian ground dove (''Gallicolumba longitarsus'')
* Viti Levu giant pigeon (''Natunaornis gigoura'')
* Marquesas cuckoo-dove (''Macropygia heana'')
* New Caledonian gallinule (''Porphyrio kukwiedei'')
* Various ''Gallirallus'' spp.
* Various Coenocorypha spp.
** New Caledonian snipe (''Coenocorypha miratropica'')
** Viti Levu snipe (''Coenocorypha neocaledonica'')
* Lowland kagu (''Rhynochetos orarius'')
* Niue night heron (''Nycticorax kalavikai'')
* Several ''Accipiter'' spp.^{Accipiter, [3]}
** Powerful goshawk (''Accipiter efficax'')
** Gracile goshawk (''Accipiter quartus'')
* New Caledonian barn owl (''Tyto letocarti'')
* ''Mekosuchus'' (two meters long, last fully terrestrial crocodile, South Pacific Islands)
* ''Volia'' (a two-to-three meter long Mekosuchinae, mekosuchine crocodylian, apex predator of Pleistocene Fiji)
* ''Varanus sp.'' (Pleistocene and Holocene New Caledonia)
* Several giant Iguanidae spp.
** ''Lapitiguana''
** ''Brachylophus gibbonsi''
* All Dinornithiformes spp.
** Giant moa (''Dinornis'')
** Upland moa (''Megalapteryx didinus'')
** Bush moa (''Anomalopteryx didiformis'')
** Eastern moa (''Emeus crassus'')
** Coastal moa (''Euryapteryx curtus'')
** ''Pachyornis''
* Scarlett's duck (''Malacorhynchus scarletti'')
* New Zealand musk duck (''Biziura delautouri'')
* Chatham Islands duck (''Pachyanas chathamica'')
* New Zealand goose (''Cnemiornis'')
* New Zealand swan (''Cygnus sumnerensis'')
* New Zealand owlet-nightjar (''Aegotheles novazelandiae'')
* Adzebill (''Aptornis'')
* Snipe-rail (''Capellirallus karamu'')
* Hodgen's waterhen (''Gallinula hodgenorum'')
* Waitaha penguin (''Megadyptes waitaha'')
* Scarlett's shearwater (''Puffinus spelaeus'')
* Several Harrier (bird), harriers (''Circus'')
** Eyles's harrier (''Circus eylesi'')
** Wood harrier (''Circus dossenus''; endemic to Hawaii)
* Haast's eagle (''Hieraaetus moorei''; largest eagle known to have existed)
* Various ''Corvus'' spp.
** New Zealand raven (''Corvus antipodum'')
** Chatham raven (''Corvus moriorum'')
** High-billed crow (''Corvus impluviatus''; large crow endemic to Maui)
* Long-billed wren (New Zealand), Long-billed wren (''Dendroscansor decurvirostris'')
* Stout-legged wren (''Pachyplichas yaldwyni'')
* Kawekaweau (''Hoplodactylus delcourti'')
* Northland skink (''Oligosoma northlandi'')
* Several frogs of the genus ''Leiopelma''
** Auroa frog, Aurora frog (''Leiopelma auroraensis'')
** Markham's frog (''Leiopelma markhami'')
** Waitomo frog (''Leiopelma waitomoensis'')
* ''Synemporion keana'' (Bat endemic to Hawaii)
* Kaua'i mole duck (''Talpanas lippa''; a blind, flightless, terrestrial Hawaiian duck)
* All members of Thambetochenini
** Turtle-jawed moa-nalo (''Chelychelynechen quassus''; from Kaua'i)
** Small-billed moa-nalo (''Ptaiochen pau''; from Maui)
** O'ahu moa-nalo (''Thambetochen xanion'')
** Maui Nui large-billed moa-nalo (''Thambetochen chauliodous'')
* Giant Hawaii goose (''Branta rhuax'')
* Nēnē-nui (''Branta hylobadistes'')
* Great Maui crake (''Porzana severnsi'')
* O'ahu petrel (''Pterodroma jugabilis'')
* ''Apteribis'' (a giant, flightless ibis)
* Stilt-owl (''Grallistrix'')
* Giant nukupu'u (''Hemignathus vorpalis'')
* Stout-legged finch (''Ciridops tenax'')
* Several finches of the genus ''Telespiza''
** Telespiza persecutrix, Kaua'i finch (''Telespiza persecutrix'')
** Maui Nui finch (''Telespiza ypsilon'')
* Kaua'i palila (''Loxioides kikuchi'')
* Several Rhodacanthis spp.
** Primitive koa finch (''Rhodacanthis litotes'')
** Scissor-billed koa finch (''Rhodacanthis forfex'')
* Wahi grosbeak, O'ahu grosbeak (''Chloridops wahi'')
* Easter Island crake (''Porzana'' sp.)
* Easter Island rail (undescribed)
* Undescribed Easter Island heron
* Barn owl (''Tyto alba''; extirpated on Easter Island)
* Two species of undescribed Easter Island parrots
Some extinct megafauna, such as the bunyip-like ''Diprotodon'', may remain in folk memory or be the sources of Cryptozoology, cryptozoological legends.

Relationship to later extinctions

There is no general agreement on where the Holocene, or Human impact on the environment, anthropogenic, extinction begins, and the Quaternary extinction event ends, or if they should be considered separate events at all. 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 Australian megafauna, Australia, List of extinct animals of New Zealand, New Zealand and List of African animals extinct in the Holocene, Madagascar, in a similar way that any Invasive species, 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 Geographical isolation, geographically isolated islands. Only during the most recent parts of the extinction have Effect of climate change on plant biodiversity, plants also suffered large losses.

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 Decline in amphibian populations, amphibian crisis being a few broader examples of an almost universal, cosmopolitan decline of biodiversity.

Hunting hypothesis

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. Therefore, 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. biogeography, Biogeographical evidence is also suggestive: the areas of the world where humans evolved currently have more of their Pleistocene megafaunal diversity (the elephants and Rhinoceros, rhinos of Asia and Africa) compared to other areas such as Australia, the Americas, Madagascar and New Zealand without the earliest humans.

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.
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.

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 and by computer models by Mosimann and Martin, and Whittington and Dyke, and most recently by Alroy.

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. This was compared against climate reconstructions for the last 90,000 years. The researchers found correlations of human spread and species extinction indicating that the Human impact on the environment, human impact was the main cause of the extinction, while climate change exacerbated the frequency of extinctions. The study, however, found an apparently low extinction rate in the fossil record of mainland Asia.

Overkill hypothesis

The overkill hypothesis, a variant of the hunting hypothesis, was proposed in 1966 by Paul Schultz Martin, Paul S. Martin, Professor of Geosciences Emeritus at the Desert Laboratory of the University of Arizona.

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. 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. A study by Surovell and Grund 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.

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 :Image:Five Myr Climate Change.png, multiple glacial :Image:Atmospheric CO2 with glaciers cycles.gif, 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.

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.

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.

Some evidence obtained from analysis of the tusks of American mastodon, mastodons from the Great Lakes region (North America), 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.

Increased temperature

The most obvious change associated with the termination of an ice age is the increase in temperature. Between 15,000 Before Present, 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 glaciation, 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, 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 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 Refugium (population biology), refugia and long distance dispersals, which may have been disrupted by human hunters.

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.

In addition, numerous species such as mammoths on Wrangel Island and Saint Paul Island (Alaska), St. Paul Island survived in human-free Refugium (population biology), 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.

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-aspen parkland, parkland to separate prairie and woodland. 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-Dietary fiber, fiber food and better able to deal with anti-herbivory toxins. 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. Axelrod and Slaughter 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 Biological life cycle, 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.

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.

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.
* 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. 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.
* 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 and on Wrangel Island in the Siberian Arctic 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. 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.
* Large animals store more fat in their bodies than do medium-sized animals 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. 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: Browser (herbivore), browsers, mixed feeders and non-ruminant grazer species suffered most, while relatively more ruminant grazers survived. However, a broader variation of the overkill hypothesis may predict this, because changes in vegetation wrought by either Second Order Predation (see below) or Human impact on the environment, anthropogenic fire preferentially selects against browse species.

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 Indigenous peoples, aboriginal humans. 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.

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 Asymptomatic carrier, carrier state in a reservoir species. That is, it must be able to sustain itself in the environment when there are no susceptible Host (biology), 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, 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.
* 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.
* 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.
*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.

Second-order predation hypothesis

Scenario

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 equilibrium, ecological balance of the continent, causing overpopulation (biology), 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, 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 (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. (results graph at right).

The second-order predation hypothesis is supported by the observation above that there was a massive increase in bison populations.

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. 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.

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.

Younger Dryas impact hypothesis

First publicly presented at the Spring 2007 joint assembly of the American Geophysical Union in Acapulco, Mexico, the Younger Dryas impact hypothesis suggests that the mass extinction was caused by fragments of a disintegrating asteroid or comet 12,900 years ago. 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.

Arguments against/for the impact hypothesis

The discredited and controversial Younger Dryas impact hypothesis claims that a comet impact or air burst occurred in North America about 12,900 years ago as the mechanism that initiated the Younger Dryas cooling.

A spike in platinum was found in the Greenland ice cores by Petaev et al. (2013), which they view as a global signal. Confirmation came in 2017 with the report that the Pt spike had been found at "11 widely separated archaeological bulk sedimentary sequences." Wolbach et al. reported in 2018 that "YDB peaks in Pt were observed at 28 sites" in total, including the 11 reported earlier and the one from Greenland.

* Some have reported a lack of evidence for a population decline among the Paleoindians at 12,900 ± 100 Calibrated years, calBP. However, others have reported finding such evidence.
* There is evidence that the megafaunal extinctions that occurred across northern Eurasia, North America and South America at the end of the Pleistocene were not synchronous as the bolide theory would predict. The extinctions in South America appear to have occurred at least 400 years after those in North America.
* Additionally, some island megafaunal populations survived thousands of years longer than populations of the same or related species on nearby continents; examples include the survival of woolly mammoths on Wrangel Island until 3700 BP, and the survival of Megalocnus, ground sloths in the Antilles until 4700 cal BP.
* Several markers for the proposed impact event are disputed. Opponents have asserted that the carbon spherules originated as fungal structures and/or insect fecal pellets, and that the claimed nanodiamonds are actually misidentified graphene and graphene/graphane oxide aggregates. An analysis of a similar Younger Dryas boundary layer in Belgium also did not show evidence of a bolide impact.
*However, proponents of the hypothesis have responded to defend their results, disputing the accusation of irreproducibility and/or replicating their findings. Prior to finding of a widespread Pt spike on the continents, Pleistocene expert Wallace Broecker had already changed his mind about the YDIH: "The Greenland platinum peak makes clear that an extraterrestrial impact occurred close to the onset of the YD."

See also

*
*
*
*
*
*
*
*

References

External links

Hyperdisease hypothesis

*
*

Second-order predation

*

Other links

*
*
*
*
*

{{DEFAULTSORT:Quaternary Extinction Event
Extinction events
Pleistocene
Events that forced the climate
Quaternary extinctions,