New genomic analysis reveals why the last isolated mammoth population on Wrangel Island went extinct!
A recent genomic analysis has revealed that the last woolly mammoth population was isolated on Wrangel Island 10,000 years ago, originated from just eight individuals and grew to 200-300 individuals within 20 generations, but later became extinct due to an unknown random event .
Genomic analysis of Wrangel Island mammoths has shown signs of inbreeding and low genetic diversity, reflecting the dynamics of the now endangered animals .
Genomic analysis underscores the importance of ongoing genetic monitoring of endangered animals to prevent the accumulation of harmful mutations .
A recent genomic analysis has revealed that the last woolly mammoth population , which lived on Wrangel Island off the coast of Siberia and was isolated 10,000 years ago by rising sea levels, lived on the island for the next 6,000 years, originating from just eight individuals. This population grew to 200-300 individuals over 20 generations, but later became extinct due to an unknown random event.
The genomes of the Wrangel Island mammoths showed signs of inbreeding and low genetic diversity, but not enough to explain their mysterious eventual extinction, researchers reported in the journal Cell on June 27.
“We can now confidently reject the idea that the mammoth population was simply too small and that they were doomed to extinction for genetic reasons,” said lead author Love Dalén, an evolutionary geneticist at the Centre for Palaeogenetics, a joint collaboration between the Swedish Museum of Natural History and Stockholm University. “This means that it was probably a random event that wiped them out, and if that random event had not happened, mammoths would still be around today.”
In addition to shedding light on woolly mammoth population dynamics, this analysis of Wrangel Island mammoths could help guide conservation strategies for today's endangered animals.
“Mammoths are an excellent system for understanding the current biodiversity crisis and what happens from a genetic standpoint when species go through a population bottleneck because they reflect the fate of many present-day populations,” said first author Marianne DeHasco, of the Center for Paleogenomics.
To understand the genomic consequences of the Wrangel Island bottleneck—an event or period of time in which a species experiences a dramatic population decline—on mammoth populations, the team analyzed the genomes of 21 woolly mammoths, including 14 from Wrangel Island and seven from land populations that predated the bottleneck. In total, the samples spanned the last 50,000 years of woolly mammoth existence, providing a window into how mammoth genetic diversity has changed over time.
Compared to their terrestrial ancestors, the genomes of the Wrangel Island mammoths showed signs of inbreeding and low genetic diversity. In addition to low overall genetic diversity, they showed low diversity in a set of genes known to play a critical role in vertebrate immune responses.
The researchers showed that the population's genetic diversity continued to decline throughout the 6,000 years that the mammoths inhabited Wrangel Island, albeit at a very slow rate, suggesting that the population size was stable until the end. Although the island's mammoth population accumulated moderately harmful mutations throughout their time on the island, the researchers showed that the population was slowly shedding the most harmful mutations.
“If an individual has a very harmful mutation, that mutation makes the individual unable to survive, and so those mutations disappear from the population over time,” DeHasco said. “But on the other hand, we see that mammoths accumulated moderately harmful mutations until they almost went extinct.”
“It is important for current conservation programmes to keep in mind that it is not enough for a population to grow back to a suitable size; it must also be actively genetically monitored because these genomic effects can persist for more than 6,000 years,” she added. This means that maintaining genetic diversity and managing harmful mutations within populations must be a key part of conservation strategies to ensure the long-term survival of species.
“What ultimately happened is still a bit of a mystery — we don’t know why they went extinct after being pretty much fine for 6,000 years, but we think it was something that happened suddenly,” Dalen said. “I would say there’s still hope of finding out why they went extinct, but there are no promises.”
It is worth noting that although the mammoth genomes analyzed in this study cover a large time period, they do not include the last 300 years of the species’ existence. However, the researchers have uncovered fossils from the mammoth’s most recent period and plan to sequence the genome in the future.
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