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Ice Age Humans Likely Played Major Role in Cave Bears’ Extinction

Researchers have long debated whether human activity or climate change precipitated the species’ demise

Europe's cave bear population started crashing around 40,000 years ago—roughly the time period when modern humans arrived on the continent ( Didier Descouens via Wikimedia Commons under CC BY-SA 3.0)
smithsonian.com

Giant cave bears weighing up to 2,000 pounds roamed the European continent for more than 100,000 years. But around 20,000 years ago, the species—officially known as Ursus spelaeus—died out under still-mysterious and oft-debated circumstances.

A new study published in the journal Scientific Reports outlines a convincing explanation for the cave bear’s demise. As Tim Vernimmen reports for National Geographic, researchers led by the University of Zurich’s Verena Schünemann used mitochondrial DNA from 59 cave bears’ remains to date the start of the species’ decline to some 40,000 years ago—long before the advent of the last ice age but right around the time that modern humans began settling in Europe.

The team’s findings support one of two leading theories regarding the animal’s downfall, suggesting that Homo sapiens, as opposed to climate change, largely precipitated the end of the cave bear.

“If not for our arrival in Europe, I don’t see any reason why cave bears should not be around today,” study co-author Hervé Bocherens of Germany’s University of Tübingen tells Vernimmen.

According to BBC News’ Helen Briggs, the research doesn’t fully discount climate change’s contribution to cave bears’ extinction. Instead, the new study posits that human hunting and habitat encroachment paved the way for losses expounded by factors including the onset of the last ice age and declining food sources. (Wear on the bears’ teeth points toward a heavily plant-based diet, but as the Washington Post’s Ben Guarino reports, more recent discoveries offer evidence that the bears also feasted on the bodies of their peers.) There “might be still a synergistic effect of both factors: human and climate,” Schünemann explains to Guarino.

Mitochondrial DNA, or mtDNA, shows that Europe’s cave bear population was stable from 200,000 to 50,000 years ago. (Per National Geographic’s Vernimmen, mtDNA is inherited from one’s mother and can provide information on past population sizes.) But around 40,000 years ago, the species’ numbers started falling, and by 20,000 years ago, the animals had vanished completely. Crucially, Guarino notes, several periods of cooling and warming occurred during the population’s stable period but did not appear to have a significant impact on the bear’s numbers, reinforcing the idea that humans were the driving force behind the species’ extinction.

Although Neanderthals lived in the same regions as cave bears prior to the arrival of Homo sapiens, Vernimmen writes that modern humans probably wielded more advanced hunting technology and were more likely to venture into cave bear territory than their older cousins. As new settlers killed cave bears—perhaps for their fur and meat or because the animals were viewed as a threat—and moved in on their habitat, members of the species simultaneously faced obstacles such as an increasingly limited territorial range and a decline in abundant vegetation. Ultimately, the animals succumbed to a range of factors, chief among them human activity.

“We can’t rewind the clock, taking humans out of the picture, and see whether the cave bears survived or not,” Axel Barlow, a biologist at Germany’s University of Potsdam who was not involved in the study, tells the Post. “The emerging picture for cave bears, shown by not only this study but also decades of careful research, is that the influx of anatomically modern humans in Europe matches very well—both in timing and geographically—with the decline in cave bear.”

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