The last woolly mammoths on earth took their final stand on a remote control Arctic island some 4,000 years ago, but the question of what sealed their fate remained a mystery. Now a genetic analysis suggests that a freak event like an extreme storm or a plague was to blame.
The findings contradict a previous theory that harmful genetic mutations caused by inbreeding led to a “genomic collapse” in the isolated population. The latest analysis confirms that although the group had low genetic diversity, a stable population of several hundred mammoths occupied the island for thousands of years before suddenly disappearing.
“We can now confidently reject the idea that the population was simply too small and that they were doomed to extinction for genetic reasons,” says Prof Love Dalén, an evolutionary geneticist at the Center for Paleogenetics, which is jointly run by the Swedish Nature Museum is managed. History and Stockholm University. “That means it was probably just some random event that killed them off, and if that random event hadn’t happened, we’d still have mammoths today.”
Woolly mammoths once roamed vast ice age Europe, Asia and the northern reaches of North America. After the global climate began to warm about 12,000 years ago, and as human hunters posed an increasing threat, they retreated northward, becoming extinct on the continent about 10,000 years ago. Rising sea levels cut off a pocket population Wrangel Islandwhich survived for another 6,000 years.
Dalén and colleagues analyzed the genomes of 13 mammoth specimens found on Wrangel and seven earlier specimens excavated on the continent, which together represent a span of 50,000 years.
The findings, published in Cell, reveals that the Wrangel population went through a severe bottleneck, reduced to just eight breeding individuals at one point. But the group recovered within 20 generations to a population of 200-300, which seems to have remained stable until the end.
Compared to their mainland ancestors, the Wrangel Island mammoth genomes showed signs of inbreeding and low genetic diversity, including in genes known to play a critical role in the vertebrate immune response. This suggests that the group would have been more vulnerable to new pathogens such as plague or bird flu.
“Mammoths are an excellent system for understanding the ongoing biodiversity crisis and what happens from a genetic point of view when a species goes through a population bottleneck, because they mirror the fate of many contemporary populations,” says Marianne Dehasque, from Uppsala . University, the first author of the paper.
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Dr. Vincent Lynch, a biologist at the University of Buffalo who was not involved in the research, said the findings provide new insights into the mammoths’ final days and raise the possibility that a genetically compromised group may not have would be able to respond to an environment. change like a new pathogen.
“Extinction, at least when it’s not at the hands of humans, usually doesn’t stem from just one cause,” he said. “This is the result of a combination of factors such as inbreeding, a small population size, an accumulation of deleterious mutations and, sometimes, bad luck.”
