Early humans in North and South America relied heavily on hunting of large mammals, including mammoths and giant ground sloths, for food and sustenance, according to newly published research by a team including two University of Wyoming archaeologists.
The findings by UW Professor Todd Surovell, Professor Emeritus Robert Kelly and colleagues from other institutions are the latest development in a long-running debate over the behaviors and movements of early Americans before the extinction of large, plant-eating animals -- such as mammoths, other elephant-like creatures, giant ground sloths and large camels -- between 11,000 and 13,000 years ago.
The new research -- published in the journal Science Advances -- also supports the idea that the animals' extinction was due primarily to hunting by humans. The paper's lead author is Ben Potter, of the University of Alaska-Fairbanks.
"Early Paleoindians were highly residentially mobile hunter-gatherers who used homogeneous technology and made unpatterned use of vast territories in the context of a rapid geographic expansion across numerous ecologically distinct regions of North and South America within a few hundred years," the researchers wrote. "Focus on megaherbivores facilitated rapid human expansion into different ecosystems before the … extinction of megafauna led to regional diversification through adaptations to locally available resources."
The new study focused on people in Eastern Beringia -- stretching from the Mackenzie River in Canada through Alaska and westward to the Bering Strait land bridge -- between 13,300-14,000 years ago; the so-called Clovis people in North America between 12,800-13,400 years ago; and the Fishtail projectile point people of South America between 11,600-12,900 years ago. The researchers synthesized the zooarchaeological records from sites in all of those regions -- including the La Prele Mammoth site in Wyoming, where Clovis people killed or scavenged a Columbian mammoth nearly 13,000 years ago -- to reach their conclusions.
For all three regions, the researchers estimate that at least 98 percent of these Early Paleondians' diet came from the large mammals. That makes sense, according to the new paper, in part because large-bodied, fat-rich prey yields relatively more calories and nutrients than smaller animals.
Additionally, the researchers note that Early Beringian people -- likely the first to enter the Americas over the Bering land bridge, according to Surovell, Kelly and others -- encountered primarily large mammals, with few potential plant resources. There is no indication of fishing by these people in the archaeological record there. So those mammals were the humans' primary food source, a relationship that continued as people moved southward through a passageway between the massive Laurentide and Cordilleran ice sheets in North America, running from modern-day Alaska through Alberta, Canada, to the Great Plains, between 12,000 and 13,000 years ago.
"When these megafauna-focused hunter-gatherers entered the midcontinent, they first encountered many of the same (and similar) species in very similar steppe-tundra ecosystems and used a similar subsistence and high-mobility strategy," the researchers wrote. "While the timing of the opening and ecological viability of the Ice-Free Corridor remains unresolved, once it was open, woolly mammoth habitat extended through the Ice-Free Corridor from Beringia to the proglacial tundras of the midwest United States. Humans shifted their subsistence focus to very similar Columbian mammoth found throughout North America as far south as highland Central America and, to a lesser extent, mastodons and gomphotheres in other North American regions. (Fishtail projectile point) populations expanding through South America tracked similar megafaunal prey, including large ground sloths (mylodonts and megatheres) and gomphotheres, and other megafauna such as camelids and equids."
The study acknowledges that other scientists have examined similar data but "interpret them in polar-opposite ways," with those interpretations leading to conclusions that the early Americans were dietary generalists, not "megafauna specialists." The new paper addresses some of the differing interpretations.
Specifically, Surovell, Kelly and colleagues say the argument that eating only large mammals would not sustain human populations nutritionally has been refuted by research showing that high-protein diets, known as keto diets, are in fact healthy.
"Except for the likely opportunistic consumption of easily obtainable fruits or nuts, these highly mobile Early Paleoindians apparently consumed a diet mostly of meats, including both protein and fat," the researchers wrote.
Additionally, they say there's a good reason that there's little evidence of the early Americans accessing bone marrow from the animals they killed or scavenged: There was plenty of food to be had without processing the bones.
"The pattern of sometimes minimal bone processing is more consistent with megafauna specialist behaviors in a resource-rich environment, where meat and fat are easily obtainable, both off the carcass and in terms of higher encounter rates, both resulting in reduced energy costs," the researchers wrote. "Overall, Early Paleoindian strategies indicate that it was more efficient to kill new animals than to fully process every kill."
And arguments that the early humans weren't capable of killing giant mammals don't hold up to the evidence, the researchers say. The tools used in hunting -- such as Clovis points and Fishtail projectile points -- were definitely capable of penetrating the hide of mammoths through the use of atlatls and spears, and the Paleoindians likely hunted in groups to increase their rate of success.
"Archaeological evidence for Early Paleoindian subsistence, technology and mobility patterns supports the contention that the first continent-wide adaptive strategies in Eastern Beringia, subglacial North America and South America were big game specialists, not dietary generalists," the paper concludes. "The pattern began with woolly mammoth exploitation in Western Beringia (Northern Siberia) in the steppe-tundra habitat and its continuation into Eastern Beringia (Alaska). Woolly mammoth habitat connected Beringia with the Ice-Free Corridor and the Great Lakes region, where hunters encountered a similar species, the Columbian mammoth, facilitating rapid expansion throughout North America.
"At the southern extremity of Columbia mammoth, as early populations entered Central America, they encountered new habitats and the megaherbivores giant ground sloths and gomphotheres. Early Paleoindians followed these new taxa through the new bottleneck of Panama into and throughout South America. The megafaunal specialization emphasis of Early Paleoindians allowed for rapid expansion requiring little change in overall adaptive strategies, resulting in the continent-wide similarities we observe in the Early Paleoindian record."
Only when the large mammals became extinct -- primarily a result of overhunting -- did the early Americans vary their diets to include smaller mammals such as bison, waterfowl, birds, fish, shellfish and plants, the researchers say.
In addition to Potter, Surovell and Kelly, members of the research team are James Chatters, of McMaster University in Hamilton, Ontario, Canada; Luciano Prates, of Universidad Nacional de la Plata in La Plata, Argentina; Ivan Perez, of the Museo Histórico y Arqueológico in Neuquén, Argentina; Gustavo Politis, of Universidad Nacional del Centro de la Provincia de Buenos Aires in Tandil, Argentina; and Matthew Wooller, of the University of Alaska-Fairbanks.
