Genes of the Last Woolly Mammoths Were Riddled with Bad Mutations, Study Finds
Before they died out, they lost their sense of smell and suffered from heartburn
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The last woolly mammoths to roam the Earth may have been sad, sickly creatures. As Nicola Davis reports for The Guardian, a new study suggests that the genomes of woolly mammoths living some 4,000 years ago were wracked with harmful mutations. The animals could not digest their food properly, leading to heartburn. Their sense of smell was damaged. Their coats, soft and silky rather than thick and wiry, could not protect them from the cold.
These woolly mammoths were the ragged vestiges of a species that had been dying out over the course of millennia. The woolly mammoth disappeared from Siberia and North America 10,000 years ago, victims of hunters and a drastically shifting climate. But small populations continued to exist on islands in the Arctic Ocean until they went extinct some 3,700 years ago.
The new study, published in PLOS Genetics, compared the genomes of two woolly mammoths. One lived in Siberia 45,000 years ago, and the other lived about 4,300 years ago on Wrangel Island, off the coast of Russia. Based on the amount of variation found in the genome of each animal, Nicholas Wade of the New York Times explains, scientists estimate that the Siberian woolly mammoth belonged to a population of about 13,000. The Wrangel mammoth, by contrast, likely lived alongside some 300 individuals.
Researchers found that the genome of the Wrangel mammoth, unlike that of its older counterpart, was riddled with mutations that would have been harmful to its health, including one that is known to cause satiny fur in mice. The mutation may have caused the mammoth to sprout “translucent hairs,” the authors of the study write. This is problematic, they note, because mammoths typically possess “a stiff outer coat that may have protected animals from cold climates.”
So-called “satin mutants” often have digestive problems, study co-author Rebekah Rogers told Davis at The Guardian, and so it is possible that the mammoth experienced heartburn.
Researchers also found mutations in the mammoth’s olfactory system, which may have led to impairments in its sense of smell. Genes relating to urinary proteins, which are known to act as pheromones, were mutated too, suggesting that the mammoth’s mating patterns may have been thrown off-kilter.
Speaking to Helen Briggs of the BBC, Rogers said that this rather unfortunate mammoth had gone into “genomic meltdown.”
Just why did its genes go so haywire? As Wade explains in the Times, natural selection becomes less efficient at weeding out bad mutations as a population dwindles. Inbreeding among the small population of mammoths on Wrangel Island may have therefore compounded the problem, leading to a slow destruction of the animals’ genetic makeup.
The study’s findings have frightening implications for today’s endangered animals. Once a species’ numbers drop below a certain level, the resulting damage to its genes could be irreversible. Conservation efforts to preserve small, endangered populations, in other words, may not be enough.
“[I]f you can prevent these organisms ever being threatened or endangered, then that will do a lot more to help prevent this type of genomic meltdown compared to if you have a small population and then bring it back up to larger numbers because it will still bear those signatures of this genomic meltdown," Rogers said in her interview with Briggs.
And as Science Daily points out, the results of the study won’t do much to advance the woolly mammoth’s “de-extinction,” which is supposedly imminent. At least some mammoth genes, it seems, are far too damaged to resurrect.