Humans A Major Factor In the Extinction of Giant Cave Bears
Until 25,000 years ago, Europe was home to some of the largest mammals, that ever lived. One of the most remarkable of the megafauna was the gigantic cave bear. Why these massive animals and other megafauna became extinct has been a subject of controversy for decades. Now a genetic analysis of the DNA of the prehistoric cave bear may show that they declined and disappeared because of the arrival of modern humans in Europe and not because of an Ice Age.
Cave bears (Ursus spelaeus) “roamed Europe for over 100,000 years” according to the New Scientist. They were as large as modern grizzly bears, weighed as much as 2000 pounds (908 kilograms) and were herbivores. A great many remains of the gigantic bears have been found in Central and Eastern Europe.
The last known remains of the extinct cave bear, discovered in a site in the Italian Julian Alps, date to approximately 25,000-24,000 years ago. They were among the last of the megafauna to disappear from Europe.
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Italian Julian Alps where the last remains of a cave bear were discovered. (lloorraa / Public Domain)
Why Did the Giant Cave Bears Disappear?
The reasons for the extinction of the cave bear has not been conclusively established. Some academics believe that they became extinct because of an Ice Age, that decimated their habitat. The National Geographic Magazine reports that “some scientists think they were victims of the Last Glacial Maximum, which peaked around 26,500 years ago”. However, others argue that the cave bear was driven to extinction by humans.
A multidisciplinary international team led by Hervé Bocherens and Verena Schuenemann conducted an analysis of the megafauna’s mitochondrial DNA. The team extracted DNA from 81 bones that had been identified as belonging to cave bears. According to Nature, the researchers were able to “generate mitochondrial sequences for 59 of the 81 specimens”. These sequences were then compared to 64 others from European cave bears.
Skull of Ursus spelaeus: Cave bears lacked the usual two or three premolars present in other bear species. (Archaeodontosaurus / CC BY-SA 3.0)
A Bayesian phylogenetic analysis was conducted on the sequences and they indicated a high level of diversity. This would indicate a relatively large and stable population size for tens of thousands of years, even though there were extreme periods of cold during this time.
According to Nature “it appears unlikely that these previous climatic fluctuations did substantially affect the cave bear population in Europe”. This would show that the megafauna survived two Ice Ages, and this is not a surprise as the mammals once roamed the Arctic Circle.
Cave Bears and Human Hunters
The team of experts established that the population began to decline when the climate was relatively warm and thousands of years before any cooling off period. Indeed, the climate did not really cool for some 20,000 years after the start of the contraction of the population. Based on the estimated dates they concluded that the bear’s numbers began to decline because of human activity.
The research team believe, based on the mitochondrial DNA, that the decline in the bear numbers around 50,000 years ago was because of an extinct human species, the Neanderthals. It appears that they hunted and competed with the animals and this led to a drop in their numbers. However, the decline in the megafauna’s population became dramatic with the migration of anatomically modern humans into Europe.
Prehistoric man hunted the cave bears into extinction. (Mutter Erde / Public Domain)
Homo sapiens were much more ferocious hunters than the Neanderthals and they had new hunting weapons such as “simple and split-based bone points” explains the study published in Nature. Moreover, they were much larger in number than the Neanderthals and were organized in groups.
This meant that they could have hunted and killed many more cave bears. They possibly killed the megafauna for their meat, fur, or just because they were seen as a menace.
Reasons for the Extinction of the Cave Bears
According to Nature, the “negative human effect on cave bear populations would have been increased at the onset of the Last Glacial Maximum”. Moreover, it seems that the animals sought refuge in remote locations such as the Italian Alps.
As a result, they increasingly became cut-off from other bears, and this may have reduced their birth-rate. The relative isolation of the bears would also have reduced their genetic diversity and led to inbreeding and this could have made them more susceptible to disease and illness, which further contributed to their demise.
Life restoration of the extinct cave bear. (Sergiodlarosa / CC BY-SA 3.0)
It appears that early humans are largely to blame for the extinction of the cave bears. Hervé Bocherens told the National Geographic, “If not for our arrival in Europe, I don’t see any reason why cave bears should not be around today”. Conservationists can learn lessons from the fate of the giant beast, especially the importance of ensuring that vulnerable species such as modern brown bears are part of a larger population to ensure genetic diversity.
Top image: Skeleton of a prehistoric cave bear. Source: Fizped / CC BY-SA 3.0
By Ed Whelan