A genetic “mutational meltdown” helped push the woolly mammoth toward extinction, according to a new study.
Researchers at the University of California, Berkeley, say they compared genetic material from mammoths when they were plentiful and material from when the population was in decline.
What they found was “genome deterioration” that reflected the smaller population size. The findings are a warning to conservationists that keeping a small pool of endangered animals could result in inbreeding and genomic meltdown.
“There is a long history of theoretical work about how genomes might change in small populations. Here we got a rare chance to look at snapshots of genomes ‘before’ and ‘after’ a population decline in a single species,” said Rebekah Rogers, who led the work as a postdoctoral scholar at Berkeley and is now an assistant professor at the University of North Carolina at Charlotte. “The results we found were consistent with this theory that had been discussed for decades.”
According to researchers, woolly mammoths were once very common in North America, Siberia and Beringia, which is the land bridge that used to exist between current day Russia and the U.S. state of Alaska.
About 10,000 years ago, in the face of a warmer climate and increased hunting by humans, the populations of the beasts began to shrink. But the woolly mammoth existed until about 3,700 years ago when they finally went extinct.
Researchers say they compared genetic materials from a 45,000-year-old mammoth to one that lived 4,300 years ago. The latter was from a group of about 300 mammoths that lived on Wrangel Island in the Arctic Ocean.
“We found an excess of what looked like bad mutations in the mammoth from Wrangel Island,” Rogers said.
Using mathematical models, researchers say they found “multiple harmful mutations” in the sample from Wrangel Island. Some of the mutations caused the mammoths to lose olfactory receptors. This led to problems with mate choice, researchers said. Furthermore, one mutation likely caused the animal to develop an “unusual translucent satin coat.”
“With only two specimens to look at, these mathematical models were important to show that the differences between the two mammoths are too extreme to be explained by other factors,” Rogers said.