The authors concluded that the second group did not evolve from the first group. Instead the younger group derived from a separate population of brown bear in Eurasia, indicating a new migration of bears. The same thing happened again sometime after 10,000 years ago, because the brown bear in this area are not the same genetically as the ones that lived here between 21,000-10,000 years ago.
"This is all kind of new and strange in terms of concepts of how ice age mammals moved and evolved and responded to climatic and environmental changes," said Matheus.
Researchers used stable isotope data to determine aspects of ancient brown bear diets and compared them to those of the extinct short-faced bear, which peak between 35-21,000 years ago. They also examined whether competition between the two would help explain the 14,000 year absence of the brown bear and the extinction of the short-faced bear around 21,000 years ago.
"We concluded that other factors probably were responsible, because the two bears were quite different ecologically," Matheus said.
Science