The American mastodon went extinct at the end of the last major ice age, and a new study shows the species was not wiped out by our distant human ancestors. When the first people migrated to Beringia, a land bridge between modern-day Alaska and Siberia, the animal was already gone, according to a new study.
Mastodons, three species of long-gone relatives of elephants, apparently disappeared from the region 50,000 years before the time paleontologists once estimated.
Radiocarbon dating of American mastodon fossils dates the beginning of occupation of the area by the animals, starting around 18,000 years ago. However, this date corresponds to a time when the region was inundated with glaciers, and ice made vegetation scarce. These conditions seem to be in conflict with the dietary needs of the giant animals. Mastodons were perfectly-suited for grazing, and would likely have fared poorly in glacial conditions.
Paleontologists and other researchers re-examined dating performed on 36 mastodon fossils, examining the specimens with newer dating techniques. This new examination provided 53 new dates, including some on fossils with previously-published ages.
Mastodons were forced from the boreal forests of the region around 75,000 years ago, as the local climate changed to steppe tundra, according to the new study. After that time, the creatures likely only moved back into the region during warmer periods, following food supplies.
After glaciers of the ice age took grip in the north, mastodons were likely driven south of continental ice sheets. There, the animals met their final demise about 100 centuries before our time.
"The new findings also indicate that mastodons suffered local extinction several tens of millennia before either human colonization - the earliest estimate of which is between 13,000 and 14,000 years ago - or the onset of climate changes at the end of the ice age about 10,000 years ago, when they were among 70 species of mammals to disappear in North America," the American Museum of Natural History, who sponsored the study, reported.
Biologists and paleontologists have been trying to piece together the circumstances of these extinctions. Although some biologists pointed at early hunters for the local extinction of the animals from Beringia, climate change could answer at least one of the mysteries surrounding the disappearance of animal species during that long-gone time.
"Was is the result of over-hunting by early people in North America? Was it the rapid global warming at the end of the ice age? Did all of these big mammals go out in one dramatic die-off, or were they paced over time and due to a complex set of factors?" Ross MacPhee, from the Department of Mammalogy at the American Museum of Natural History, said.
The extinction of the mastodon, and comparisons to human habitation of Beringia, was detailed in the Proceedings of the National Academy of Sciences of the United States of America.
