About 4,000 years ago, the last woolly mammoths of Earth took refuge on a remote Arctic island, Wrangel. Their extinction has remained an enigma for centuries, but recent genetic analyses have shed light on this historical mystery.
Contrary to the theory of a “genomic collapse” caused by harmful genetic mutations due to inbreeding, new research suggests that a random event, such as an extreme storm or plaguemay have been the final straw for these prehistoric giants. This study contradicts the idea that low genetic diversity doomed mammoths to extinction.
Professor Love Dalén, evolutionary geneticist at the Centre for Palaeogeneticshe confidently states: “We can now reject the idea that the population was simply too small and was doomed to extinction for genetic reasons. This means that it probably It was just a random event that killed themand if that event hadn’t happened, we would still have mammoths today“.
Woolly mammoths once roamed the vast expanses of Europe, Asia and North America during the Ice Age. With global warming started about 12,000 years ago and the growing threat of human hunters, retreated northward, becoming extinct on the mainland about 10,000 years ago. Rising sea levels isolated a remnant population on Wrangel Island, which survived for another 6,000 years.
Dalén and his colleagues analyzed the genomes of 13 mammoth specimens found on Wrangel and seven earlier specimens excavated on the mainland, representing a time span of 50,000 years. The results, published on Cellreveal that the Wrangel population suffered a severe genetic bottleneck, dwindling to just eight reproductive individuals. However, the group recovered to a population of 200-300 individuals within 20 generations, remaining stable until the end.
Comparing the genomes of Wrangel Island mammoths with those of their mainland ancestors, signs of consanguinity are noted and low genetic diversity, including genes that play a critical role in vertebrate immune response. This suggests that the group would have been more vulnerable to new pathogens, such as plague or avian influenza.
Marianne Dehasque, from Uppsala University and first author of the study, says: “Mammoths are an excellent way to understand the current biodiversity crisis and what happens from a genetic point of view when a species goes through a demographic bottleneck, as reflect the fate of many populations today“.
Extinction, at least when it is not caused by humans, it does not usually arise from a single cause. It is the result of a combination of factors such as inbreeding, small population size, accumulation of harmful mutations and, sometimes, bad luck.
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