On Arctic island, last woolly mammoths had genetic 'meltdown'

But, at the end of the last ice age, about 10,000 years ago, their population suddenly declined.

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.

In 2015, a group of researchers from a variety of universities published a study in which they extracted DNA from the molar tooth of a mammoth from Wrangle Island in the Arctic Ocean that was about 4,300 years old, and from the soft tissue of a juvenile mammoth from Siberia that dated to about 44,800 years ago.

But with such a small population, there would have been no mechanism to prevent these mutations from being passed on to the next generation of mammoths.

A few woolly mammoths survived north of the eastern tip of Siberia after they endured for almost 6,000 years after the species of the mainland had vanished. For those interested in wooly mammoth "de-extinction", the study demonstrates that some mammoth genomes carry an overabundance of negative mutations.

Woolly mammoths became totally extinct almost 4,000 years ago, and a team of geneticists have now deciphered the probable reason for the ancient huge species' demise. As such, harmful changes in the mammoth genome that deleted large chunks of DNA, or messed up how genes were read and translated, would have accumulated, according to Rogers. It's possible that, in an island environment that lacked predators, once useful genes were no longer that necessary, or that the tiny population meant that unusual variations and random mutations would remain in the population.

"The animals had lost many olfactory receptors, which detect odors, as well as urinary proteins, which can impact social status and mate choice", said the study in PLOS Genetics, describing the process as a "genomic meltdown in response to low effective population sizes".

Others likely led to a more satiny, glossy coat than the animal's typical stiff-haired exterior - a change that could have made them more vulnerable to cold temperatures. These genetic mutations continued and ended up moving so rapidly that the woolly mammoths became extinct much sooner than they would have if these mutations hadn't taken place.

What they found was "genome deterioration" that reflected the smaller population size.

Rogers said mathematical models developed by Monty Slatkin, a Berkeley professor, of how genomes change as population conditions change were key to analyzing the genomes.

"We would expect that if you got another mammoth from the island and you looked at its genome, that it would also have an excess of bad mutations", Rogers told Live Science.

"It makes sense that the researchers would find an accumulation of deleterious mutations in a population that was very small", said Beth Shapiro, an evolutionary biologist at the University of California, Santa Cruz, who was not involved in the new study. The findings are a warning to conservationists that keeping a small pool of endangered animals could result in inbreeding and genomic meltdown.

  • Carolyn Briggs