Genetic ‘Meltdown’ Linked to Woolly Mammoths’ Demise

Wooly mammoths near the Somme River, American Museum of Natural History mural. (Credit: Charles R. Knight, Public Domain, Wikimedia Commons)

(CN) – The last population of woolly mammoths suffered from a “mutational meltdown” in their genomes that interfered with gene functions and ultimately led to their extinction.

In a study published Thursday in the journal PLOS Genetics, researchers at the University of California, Berkeley, report on the negative impacts of limited genetic variation observed in the last population of woolly mammoths which lived until about 3,700 years ago.

Woolly mammoths were one of the most common large herbivores in North America and Siberia, but human hunters and a warming climate led to a massive population die-off about 10,000 years ago. The last of the species survived in small island populations.

In the new study, researchers analyze the genome of a mainland mammoth that dates back to 45,000 years ago – when the general population was large – with the genome of one that lived about 4,300 years ago. The recent genome came from a mammoth that lived in a group of about 300 animals on Wrangel Island in the Arctic Ocean.

The analysis shows the island mammoth had accumulated several harmful mutations in its genome that interfered with gene functions. The animals had lost many odor-detecting receptors, as well as urinary proteins – factors that can affect mate choice and social status. The genome also revealed that the mammoth had specific mutations that likely created an unusual, translucent satin coat.

“When I first started this project, I was excited to be working with the new woolly mammoth sequences, published by Love Dalen’s lab,” co-lead author Rebekah Rogers said. “It was even more exciting when we found an excess of what looked like bad mutations in the mammoth from Wrangel Island.”

The study warns that preserving a small group of isolated animals cannot sufficiently prevent the negative effects of genomic meltdown and inbreeding.

The team’s research also supports existing theories of genome deterioration stemming from small population sizes.

“Here we got a rare change to look at snapshots of genomes ‘before’ and ‘after’ a population decline in a single species,” Rogers said. “The results we found were consistent with this theory that had been discussed for decades.”