| MEGAFAUNA EXTINCTIONS James S. Aber |
| Paleo-Indians | Overkill hypothesis |
| Overkill inconsistencies | Related sites & references |
|
| MEGAFAUNA EXTINCTIONS James S. Aber |
| Paleo-Indians | Overkill hypothesis |
| Overkill inconsistencies | Related sites & references |
The horse, camel, mammoth, mastodon, giant ground sloth, llama, giant beaver, glyptodont, giant peccary, woodland muskox, sabertoothed cat, cheetah, and many others all became extinct in North America during this interval. The bones of many of these animals are found in kill sites with obvious evidence of slaughtering and butchering by Paleo-Indians. Buffalo (Bison sp.) was also hunted in very large numbers. Three phases of Paleo-Indian development and hunting ability are recognized in the Great Plains region--see Fig. 18-2.
| The giant ground sloth, Eremotherium, which lived in the Americas during the Pleistocene. It stood about 6 m (20 feet) tall--larger than a modern grizzly bear. Taken from the Smithsonian Photographs Online. |
| Smilodon, an extinct Pleistocene sabertoothed cat, about the size of a modern lion. Taken from the Smithsonian Photographs Online. |
| Bison bison, modern buffalo herd at Wind Cave National Park, South Dakota. |
Overkill hypothesis
The land animals most affected by late Pleistocene extinction were large
herbivores and their dependent large carnivores. Similar late Pleistocene
extinctions of large land animals took place in South America, Eurasia,
and Australia, in each case associated with big-game hunters. Paleolithic
cave paintings in Europe are among the most spectacular archeologic evidence
for coexistence of early man and now-extinct Ice Age animals. Other extinctions
occurred later on more remote islands, whenever man arrived during the Holocene.
Well documented islands include New Zealand (moas) and
Madagascar (giant lemurs, piggy hippo, etc.).
Small mammals, birds, reptiles, fish, and invertebrate animals suffered fewer extinctions. Land plants likewise experienced few extinctions, although much migration took place. The Pleistocene/Holocene transition in marine environments also had few plant or animal extinctions, except for large marine mammals that were hunted in coastal waters. On this basis the late Pleistocene extinction of large land mammals seems unbalanced.
Based on the association of kill sites and bones of extinct animals, some archeologists have concluded that the extinctions were brought about by overhunting. This overkill hypothesis certainly applies to geographically isolated regions, such as New Zealand, and there is no question that some of the now-extinct animals were killed occasionally by prehistoric man. However, much debate and controversy continue for this hypothesis as a global explanation for late Pleistocene extinctions.
Only one extinct animal, the mammoth, was a major resource for Clovis hunters; however a dwarf mammoth was able to survive on Wrangel Island in the Arctic Ocean until only 4000 years ago. Furthermore, the one animal hunted in greatest numbers, the buffalo, survived to modern time, albeit as a smaller form. In Europe, the horse and aurochs were favored prey. Both were domesticated in prehistoric times; both also survived as wild animals until historical times.
| Complete aurochs skeleton recovered from a Danish peat bog. Aurochs were the wild ancestors to modern domestic cattle. The aurochs survived in a wild state in forests of eastern Europe until Medieval times. The colored circles on this skeleton indicate wounds inflicted by stone age hunters. |
| Closeup view of fatal wound, in which a spear pierced the scapula and penetrated the animal's rib cage. This animal stumbled into a peat bog and eluded its hunters. Displayed at the National Museum of Denmark. |
Extinctions took place at the same time in other parts of North America, for which an overkill explanation does not apply. On the Colorado Plateau, for example, Paleo-Indian archeologic remains are not associated with the youngest, now-extinct, large-mammal fossils--see Figs. 18-3 and 18-4. Likewise, mammoth lived at high elevations in the Rocky Mountains, where there is no evidence for Paleo-Indian hunters.
| Mammoth tooth found at Florissant Fossil Beds National Monument, Colorado at 8400 feet (2500 m) altitude. Top view of M1 or M2 tooth from anterior portion of jaw. The tooth is radiocarbon dated at 49,830+3290 years old, which indicates a pre-late Wisconsin, probably late Pleistocene age. Scale bar in cm; photo courtesy of S. Veatch. |
| Side view of mammoth tooth fragment. Species is identified as Columbian mammoth, and the individual's age was probably in late teens or early twenties at the time of death, but could have been as old as late thirties. Scale bar in cm; photo courtesy of S. Veatch. |
It seems more likely that radical changes in climate and vegetation at the end of the last glaciation led to the demise of these large mammals. Large herbivores are particularly vulnerable to such environmental changes. Large animals naturally suffer more during environmental changes and food shortages than do smaller animals. Use of fire as a hunting technique might have hastened the forest-to-grassland conversion. For large animals under stress from diminished food resources, use of fire and predation by big-game hunters might have been the proverbial "straw that broke the camel's back."
| Spring burning in the Flint Hills tallgrass prairie, east-central Kansas. Prairie fire renews the grass and eliminates trees and woody vegetation. Photo date 4/94; © by J.S. Aber. |
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References
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ES 331/767 © J.S. Aber (2006).
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