Pleistocene megafauna is the set of large animals that lived on Earth during
the Pleistocene epoch and went extinct during the Quaternary extinction event.
Megafauna is a term used to describe an animal with an adult body weight of over
44 kg. Paleoecology
The last glacial period, commonly referred to as the 'Ice Age', spanned
125,000 to 14,500 years ago and was the most recent glacial period within the
current ice age which occurred during the last years of the Pleistocene era.
The Ice Age reached its peak during the last glacial maximum, when ice sheets
commenced advancing from 33,000 years BP and reached their maximum positions
26,500 years BP. Deglaciation commenced in the Northern Hemisphere approximately
19,000 years BP, and in Antarctica approximately 14,500 years BP which is
consistent with evidence that this was the primary source for an abrupt rise in
the sea level 14,500 years ago. A vast Mammoth steppe stretched from
Spain across Eurasia and over the Bering land bridge into Alaska and the Yukon
where it was stopped by the Wisconsin glaciation. This land bridge existed
because more of the planet's water was locked up in glaciation than now and
therefore the sea-levels were lower. When the sea levels began to rise this
bridge was inundated around 11,000 years BP. During the last glacial maximum, the
continent of Europe was much colder and drier than it is today, with polar
desert in the north and the remainder steppe or tundra. Forest and woodland
was almost non-existent, except for isolated pockets in the mountain ranges
of southern Europe. The fossil evidence from many continents
points to the extinction mainly of large animals at or near the end of the last
glaciation. These animals have been termed Pleistocene megafauna. The most
common definition of megafauna is an animal with an adult body weight of over
44 kg. Across Eurasia, the Straight-tusked elephant became extinct
between 100,000–50,000 years BP. The hippopotamus, interglacial rhinoceros,
cave bear, and heavy-bodied Asian antelope died out between 50,000-16,000
years BP. The spotted hyena, woolly rhinoceros, gomphotheres, mastodon and
mammoths died out between 16,000-11,500 years BP. The musk ox largely died out
after 11,500 BP, as did the giant deer with the last pocket having survived
until about 7,700 years BP in western Siberia. Somewhat isolated from human
hunters, pockets of dwarf mammoths survived on the Channel Islands off
Southern California and off northeastern Siberia at Wrangel Island until 4,500
years BP. As some species became extinct, so too did their predators.
Among the top predators, the sabre-toothed cat died out 28,000 years
BP, the cave lion 11,900 years BP, and the leopard in Europe died out 27,000
years BP. The Late Pleistocene was characterized by a series of severe and
rapid climate oscillations with regional temperature changes of up to 16°C, which
has been correlated with megafaunal extinctions. There is no evidence of
megafaunal extinctions at the height of the LGM, indicating that increasing cold
and glaciation were not factors. Multiple events appear to also involve
the rapid replacement of one species by one within the same genus, or one
population by another within the same species, across a broad area.
Modern human's ancestors first appeared in East Africa 195,000 years ago. Some
migrated out of Africa 60,000 years ago with one group reaching Central Asia
50,000 years ago. From there they reached Europe, with human remains dated
43,000-45,000 years BP discovered in Italy, Britain, and in the European
Russian Arctic 40,000 years ago. Another group left Central Asia and reached the
Yana River, Siberia, well above the Arctic circle 27,000 years ago. Modern
humans then made their way across the Bering land bridge and into North
America between 20,000-11,000 years ago, after the Wisconsin glaciation had
retreated but before the Bering land bridge became inundated by the sea.
These people then populated the Americas. In the Fertile crescent the
first agriculture was developing 11,500 years ago.
Theories Four theories have been advanced as
likely causes of these extinctions: hunting by the spreading humans,
climatic change, spreading disease, and an impact from an asteroid or comet.
These factors are not necessarily exclusive: two or more may have combined
to cause the extinctions. Regions affected
= North America= Pleistocene fauna in North America
included giant sloths; short-faced bears; several species of tapirs;
peccaries; the American lion; giant tortoises; Miracinonyx; saber-toothed
cats like Smilodon and the scimitar cat, Homotherium; dire wolves; saiga;
camelids such as two species of now extinct llamas and Camelops; at least
two species of bison; stag-moose; the shrub-ox and Harlan's muskox; 14 species
of pronghorn; horses; mammoths and mastodons; the beautiful armadillo and
the giant armadillo-like Glyptotherium and giant beavers as well as birds like
giant condors and other teratorns. The nine-foot sabertooth salmon lived at the
time as well. In contrast, today the largest North American land animal is
the American bison. = South America=
South American wildlife in the Pleistocene varied greatly, an example
is the giant ground sloth, Megatherium. The continent also had quite a few
grazers and mixed feeders such as the camel-like litoptern Macrauchenia,
Cuvieronius, Stegomastodon, Doedicurus, Glyptodon, Hippidion and Toxodon. The
main predator of the region was Smilodon, which crossed the land bridge
between North and South America one million years ago.
= Australia= Australia was characterized by
marsupials, monotremes, crocodilians, testudines, monitors and numerous large
flightless birds. Pleistocene Australia also supported the large short-faced
kangaroo, Diprotodon, the marsupial lion, the flightless birds Genyornis and
Dromornis, the 5-meter snake Wonambi and the giant lizard, the megalania.
= Eurasia= As with South America, some elements of
Eurasian megafauna were similar to those of North America. Among the most
recognizable Eurasian species are the woolly mammoth, steppe mammoth,
straight-tusked elephant, aurochs, steppe bison, cave lion, cave bear, Cave
hyena, Homotherium, Irish elk, giant polar bears, woolly rhinoceros, Merck's
rhinoceros, narrow-nosed rhinoceros, and Elasmotherium. In contrast today the
largest European land mammal is the European bison or Wisent.
= Insular= Many islands had unique megafauna that
went extinct upon the arrival of humans more recently. These included giant bird
forms in New Zealand such as the moas and Harpagornis; giant lemurs, including
Megaladapis and Palaeopropithecus species and Archaeoindris, a
gorilla-sized lemur, two species of hippopotamus, a giant tortoise, the
Voay-crocodile and the gigantic Aepyornis in Madagascar; various giant
tortoise species from the Mascarenes, a dwarf Stegodon on Flores and a number of
other islands; dwarf woolly mammoths on Wrangel Island and St. Paul Island; land
turtles and crocodiles in New Caledonia; giant owls and dwarf ground sloths in
the Caribbean; giant geese and moa-nalo in Hawaii; and dwarf elephants and dwarf
hippos from the Mediterranean islands. See also
Holocene extinction Megafauna
Quaternary extinction event Walking with Beasts
References External links
"Ice Age Bay Area". "The Extinct Late Pleistocene Mammals of
North America". "End of the Big Beasts".
"Of mice, mastodons and men: human-mediated extinctions on four
continents". "Return to the Ice Age: The La Brea
Exploration Guide". "Large Collection of European Ice Age
Megafauna Fossils: The World Museum of Man Collection".