Now an international team of scientists analyzing DNA in 17 newly identified fossils of cave bears has revealed the decline started 50,000 years ago, “much earlier than previously suggested, at a time when no major climate change was taking place, but which does coincide with the start of human expansion,” said researcher Aurora Grandal-D’Anglade at the University of Coruña in Spain.
The scientists compared 59 DNA sequences from cave bear mitochondria – the powerhouses within their cells – with 40 modern and fossil DNA samples from brown bears (Ursus arctos) to find out why the former went extinct while the latter did not.
Their findings suggest that cave bear genetic diversity – a clue to how many there were – began declining 50,000 years ago. Other fossil evidence reveals they ceased to be abundant in Central Europe roughly 35,000 years ago. (Diversity of genes can provide indirect evidence for the number of breeding individuals, because with more bears mating more genes are thrown into the mix, and vice versa.)
“This can be attributed to increasing human expansion and the resulting competition between humans and bears for land and shelter,” Grandal-D’Anglade explained.