The results of a new study by German scientists suggest that the disappearance of mammoths and another megafauna in North America at the end of the Pleistocene was related to climate change, rather than the arrival on the continent of the first humans and their extermination of large animals. The paper is published in the journal Nature Communications.
Late Pleistocene North America was home to many large animals, such as mammoths, mastodons, giant sloths, giant beavers, and armadillo-like glyptodons. But about 12,000 years ago, most of the megafauna disappeared.
At one time it was hypothesized that the cause of extinction was the arrival to North America 14,000 years ago of modern humans, hunters of “big game. Proponents of this hypothesis argued that large animals, which were themselves at the top of the food chain, were not prepared to face an armed, well-socialized opponent and served as easy prey.
It is known that at the end of the Pleistocene, about 12,800 years ago, after several millennia of general warming, the climate suddenly returned abruptly to a glacial phase called the Late Dryas. This was the last major cooling on Earth.
Scientists from the Extreme Events Research Group at the Max Planck Institute for Chemical Ecology in Jena have found strong evidence, using a new statistical approach, that climate change, rather than rapid increases in human populations and overhunting, was the main cause of the extinction of North America’s largest mammals in the Late Dryas.
“The usual approach has been to try to time the extinction of megafauna and see how it correlates with the arrival of humans in the Americas or some climatic event,” Mathew Stewart, one of the authors of the study, quoted in a press release from the institute. – But extinction is a process, which means it unfolds over a period of time, so to understand what caused the North American megafauna to disappear, it’s important to understand how populations fluctuated before extinction. Without that, everything we see could be considered mere coincidence.”
The researchers used an innovative method of estimating populations of prehistoric hunter-gatherer and extinct animal groups developed by Christopher Carleton, one of the study’s authors. This method, called radiocarbon dating of events (REC), is based on the use of radiocarbon data as an indicator of past population size.
Its essence is that the more people and animals are present in the landscape, the more carbon remains after they have disappeared, which is then reflected in the archaeological and fossil record. In addition, unlike traditional approaches, the new method better accounts for the uncertainty of fossil dates.
Modeling results based on the REC method showed that populations of large mammals fluctuated in response to dramatic climate change: first increasing during a warming period that began about 14,700 years ago, and then declining with the onset of a 12,900-year cooling, which eventually led to a decline.
Nevertheless, the authors do not deny that humans may also have been involved in the disappearance of Pleistocene megafauna, but only indirectly and not as a major factor, as simple overhunting models suggest.