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Genetic twist in the tale of the last woolly mammoths

About 10,000 years ago, a small population of woolly mammoths were isolated on Wrangel Island off the Siberian coast. This isolation was a result of rising sea levels, a phenomenon that’s all too familiar today. 

Within just two generations, the woolly mammoth population on Wrangel Island exploded from a mere eight individuals to as many as 300 members.

Contradicting assumptions about woolly mammoths 

In a fascinating study, a genomic analysis was conducted on these mammoths, dispelling the long-believed notion that inbreeding and low genetic diversity could be blamed for their ultimate demise. 

Love Dalén, an evolutionary geneticist at the Center for Paleogenetics, a joint initiative of the Swedish Museum of Natural History and Stockholm University, sheds light on this topic.

“We can now confidently reject the idea that the population was simply too small and that they were doomed to go extinct for genetic reasons,” said Dalén. “This means it was probably just some random event that killed them off, and if that random event hadn’t happened, then we would still have mammoths today.”

Woolly mammoths and modern conservation 

The research does not just provide insights into the extinction of woolly mammoths. It also holds valuable lessons for modern-day conservation strategies and the battle against the ongoing biodiversity crisis.

“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 a lot of present-day populations,” said study lead author Marianne Dehasque, also a scientist at the Center for Paleogenetics.

Dehasque and her team conducted extensive genomic analyses of 21 woolly mammoths, including 14 from Wrangel Island and 7 from the mainland that lived before the population bottleneck. Their analysis spanned roughly 50,000 years of mammoth history, tracing the genetic diversity over time.

Tracing the genetic journey

The results of the analyses were intriguing. The Wrangel Island mammoths exhibited signs of inbreeding and reduced genetic diversity. 

However, this decrease in diversity was a slow process, visible over the 6,000 years they inhabited the island. This suggests that the population remained stable until their sudden disappearance.

“If an individual has an extremely harmful mutation, it’s basically not viable, so those mutations gradually disappeared from the population over time, but on the other hand, we see that the mammoths were accumulating mildly harmful mutations almost up until they went extinct,” explained Dehasque. 

“It’s important for present day conservation programs to keep in mind that it’s not enough to get the population up to a decent size again; you also have to actively and genetically monitor it because these genomic effects can last for over 6,000 years.”

This gives us an important lesson for current conservation efforts, indicating it’s not just about increasing the population size, but also actively monitoring the genomic health.

Mystery of the mammoths

The team didn’t include genomes from the final 300 years of the mammoths’ existence in their study. However, they plan to sequence fossils from this period to understand the extinction event even better.

“What happened at the end is a bit of a mystery still – we don’t know why they went extinct after having been more or less fine for 6,000 years, but we think it was something sudden,” said Dalén. “I would say there is still hope to figure out why they went extinct, but no promises.”

The study is published in the journal Cell.


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