ES 331/767 Lecture 18

James S. Aber

Table of Contents
Earliest Americans Paleo-Indians
Overkill hypothesis Inconsistencies

Earliest Americans

The oldest well-dated archaeologic site in the Americas is Monte Verde in southern Chile. Known since the 1970s, recent radiocarbon dating has confirmed an age of ~14,000 years BP (Wayman 2008). This site implies early man migrated into the Americas via a Pacific coastal route at least a millennium before inland population became established. The Monte Verde people had a sophisticated understanding of marine and coastal resources.

This site dates from the late Wisconsin, when large ice sheets existed in North America and Eurasia; in fact the Des Moines lobe surged to its greatest extent at almost exactly the same time (see Fig. 10-5). Meanwhile global sea level was at least 100-120 m lower than today. Although Monte Verde is well documented, little else is known about these earliest Americans. Most of the fossil evidence is likely underwater on the Pacific continental shelf. Human population and archaeologic evidence increased for inland portions of the Americas after ~12,000 years BP, as the late Wisconsin glaciation came to an end and sea level rose.


The earliest widespread archaeologic cultures of the North American Great Plains, called Paleo-Indians, date from latest glacial and early Holocene time, 12,000 to 7000 radiocarbon years ago—see Fig. 18-1. Paleo-Indians were big-game hunters, who coexisted with many now-extinct animals at the close of the Pleistocene. The appearance of Paleo-Indians coincided with changing climatic and vegetation conditions and was associated with disappearance of many large animals.

North American Pleistocene megafauna
Pleistocene fossils displayed at the Sam Noble Museum. Left: Smilodon from Los Angeles, California. Right: Bison latifrons was the largest bison ever, composite skeleton.
Left: Arctodus, giant short-faced bear, was a formidable predator, specimen from Indiana. Right: Columbian Mammoth, the largest of all mammoths, composite skeleton from Oklahoma. Photos by JSA.

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 huge numbers. Three phases of Paleo-Indian development and hunting ability are recognized in the Great Plains region—see Fig. 18-2.

  1. Clovis - kills of single or few mammoths plus a few other single animals, natural traps utilized, small family hunting groups; best dates are 11,500 to 11,000 years BP.

  2. Folsom - kills of archaic, long-horned buffalo (Bison antiquus), surround hunting technique, dozens of animals per kill, small-tribe hunting groups; best dates are 11,000 to 9000 years BP.

  3. Plano - kills of near-modern or modern buffalo (Bison bison) by the hundreds, large-tribe hunting groups; range of dates are from 10,000 to 7000 BP.

Left: 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. Right: Smilodon, an extinct Pleistocene sabertoothed cat, about the size of a modern lion. Taken from the Smithsonian.
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 archaeologic evidence for coexistence of early man and now-extinct Ice Age animals—see
Chauvet-Pont-d'Arc Cave. 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.).

Reconstructed mammoth hunter dwelling from the late Pleistocene of central Europe (Ukraine, Poland). The framework is made of mammoth bones and tusks and covered with hides; the structure stands about 2 m tall. Photo by J.S. Aber; see Mammoth Site.

Small mammals, birds, reptiles, fish, and invertebrate animals suffered fewer extinctions. Land plants likewise experienced few extinctions, although much migration took place (see Fig. 11-11). 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 archaeologists 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.

Overkill inconsistencies

The Australian giant bird,
Genyornis newtoni, along with other last-surviving megafauna went extinct some 50,000 to 45,000 years ago. This is usually attributed to the arrival of early man in the continent. However, it was also the time of major hydrologic changes and rapid drying of major basins, as documented in Lake Eyre. Climatically driven ecosystem collapse may have contributed to megafauna extinctions (Cohen et al. 2015).

In North America, Paleo-Indians did not become efficient hunters, able to kill large numbers of large animals, until after most of the extinctions were finished. The historical Indian buffalo hunts of the nineteenth century are probably not realistic for earlier times. Paleo-Indians hunted on foot armed only with hand-held spears tipped with well-made stone points. The spear thrower (atlatl) and bow and arrow were developed much later.

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. Photos by JSA; 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 (left) and side view (right). 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. The tooth is radiocarbon dated at 49,830+3290 years old. Scale bar in cm; photos courtesy of S. Veatch.
Mammoth bone site at Hot Springs, South Dakota. Array of bones (left) and nearly complete skull (right) displayed in situ. Dozens of mammoths males (but no females) are preserved in a sinkhole trap dating from ~26,000 years ago. There is no evidence that mammoth hunters were involved with this site. Photos © J.S. Aber; see Mammoth Site.

A detailed study of small-mammal diversity in Spain during the late Pleistocene and Holocene revealed some interesting trends (López-Garcia et al. 2013).

It seems likely that radical changes in climate and vegetation at the end of the last glaciation led to the demise of many 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 by J.S. Aber.


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