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Researchers have extracted DNA from a 115,000-year-old polar bear jawbone and used it to research the genetic relationship between these Arctic predators and their brown bear cousins (grizzlies included). They discovered that polar bears intermixed with brown bears fairly a bit over the millennia.
Polar bear fossils are uncommon, and plenty of of these which might be discovered are comparatively younger. However scientists bought fortunate simply over a decade in the past, when a 130,000-to-115,000-year-old polar bear jawbone was found in Svalbard.
The latest group produced a brand new, extra full genome extracted from that historical bear’s tooth, and in contrast it with the genomes of 64 trendy polar and brown bears. Their analysis is printed this week within the Proceedings of the Nationwide Academy of Sciences.
“It’s onerous to take a look at polar bears and polar bear evolution with out additionally brown bear evolution and brown bears, as a result of they’re so intently associated,” mentioned Charlotte Lindqvist, a biologist on the College at Buffalo and lead writer of the paper, in a cellphone name with Gizmodo. “Clearly, they’ve had a reasonably intertwined evolutionary historical past, the place they’ve been mixing their DNA all through their historical past after they break up into separate lineages.”
Polar bears and brown bears diverged as species between 1.3 million and 1.6 million years in the past, Lindqvist mentioned. Although the 2 species look fairly completely different right now, they interbred after their divergence, a course of that noticed extra genes from brown bears movement into polar bears, in accordance with the latest analysis.
In different phrases, trendy polar bears are genetically admixed with brown bears. Actually, earlier analysis suggests that each one dwelling polar bears right now descended from a bunch of brown bears that lived in Eire and mated with “pure” polar bears throughout the Pleistocene Epoch.
“We’re seeing a dominant sign of gene movement going into polar bears, which then means that polar bears as a species have inherited DNA from brown bears,” Lindqvist mentioned. “Since they’re such completely different species—the polar bears being Arctic specialists and the brown bears being extra generalist—you may ask what sort of impression would possibly which have on the polar bear as a species.”
It’s inconceivable to say what these historical polar bears may need been like with out extra fossil proof. As a result of a lot of the animals stay and die on ice sheets (which have reduced in size and disappeared altogether lately), most historical polar bear bones are in all probability sitting on the underside of the Arctic Ocean.
Sooner or later, the researchers state within the paper, the 2 species will come into elevated contact as sea ice melts as a consequence of local weather change. These interactions enhance the chance of interbreeding.
In idea, the 2 species may “soften collectively” in the same approach to how early trendy people subsumed Neanderthals into their populations, Lindqvist mentioned, although the bears’ breeding seasons don’t overlap a lot, and the interbreeding is extra more likely to be in probability encounters than a widespread phenomenon. Such occasions received’t save the animals, as habitat loss and different local weather change-related issues will seemingly counter any type of diversifications ensuing from the species’ interbreeding. “The tempo of environmental change is so fast,” Lindqvist added. “The query is: can they sustain?”
Intercourse received’t save the polar bear; it’s fully as much as people how a lot of the apex predators’ habitat stays intact. However by studying extra about the place these bear species got here from and the way they’ve interacted prior to now, we are able to make some guesses about the place the 2 species are going.
Extra: You Can Now Go to Polar Bears in an Electrical Tundra Buggy
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