Many large mammals died out at the end of the Pleistocene when the last glacial period came to a close. Although extinct, some of these animals were able to transmit something forward – their genes. This turns out to be the case for the cave bears that went extinct 24,000 years ago and whose DNA has been found in the genomes of living brown bears.
As reported in Nature Ecology & Evolution, researchers have found that between 0.9 and 2.4 percent of the genomes of all brown bears they investigated originated from cave bears. Thanks to interbreeding, it appears that some of the DNA of the extinct animal has persisted.
“By any standard definition, [cave bears] are extinct, but it doesn’t mean that their gene pool is erased, because they continue to live on in the genomes of these living animals,” lead author Axel Barlow, from University of Potsdam, told National Geographic.
The team compared the genomes of both brown bears and polar bears with ear bone samples from four cave bears dated to over 35,000 years ago. Genomes are not easy to read: they contain a lot of information we don’t understand, distant species might have the same genes by chance, and individuals from the same species might not share the same genes. However, the team noticed that cave bears and brown bears shared more genes than either species did with polar bears. This was not a coincidence.
“If we get an overabundance of genome positions where cave bears and brown bears are showing more similarity to each other than to polar bears, then something else must have happened,” added Barlow. “And that something is hybridization between the two species.”
Genes from extinct species have popped up in several species, including humans. Up to 4 percent of the non-African human genome is from Neanderthals. Last week, a hominid fossil was shown to be a hybrid of a Neanderthal mom and a Denisovan (another species of human) dad. Modern humans are more closely related to these two species than brown bears are to cave bears. This study raises some interesting ideas about the concept of species, extinction, and just how tenacious some genes can be.
[H/T: National Geographic]