Genetic twist in the tale of the last woolly mammoths

About 10,000 years ago, a small population of woolly mammoths was isolated on Wrangel Island off the coast of Siberia. This isolation was the result of sea level rise, a phenomenon that is well known today.

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

Conflicting assumptions about woolly mammoths

In a fascinating study, a genomic analysis was performed on these mammoths, disproving the long-held notion that inbreeding and low genetic diversity could be to blame for their eventual 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 extinction for genetic reasons,” Dalén said. “That means it was probably just a random event that killed them off, and if that random event hadn’t happened, then we’d still have mammoths today.”

Woolly mammoths and modern conservation

The research doesn’t just provide insight into the extinction of woolly mammoths. It also holds valuable lessons for modern conservation strategies and the battle against the ongoing biodiversity crisis.

“Mammoths are an excellent system for understanding the ongoing biodiversity crisis and what happens genetically when a species goes through a population bottleneck, because they mirror the fate of many populations today,” said study lead author Marianne Dehasque. , also a scientist at the Center for Paleogenetics.

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

Tracing the genetic journey

The results of the analysis were intriguing. Wrangel Island mammoths showed signs of blood clotting and reduced genetic diversity.

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

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

“It is important that today’s conservation programs keep in mind that it is not enough for the population to grow back to a good size; you also have to monitor it actively and genetically because these genomic effects can last for more than 6,000 years.”

This teaches us an important lesson for current conservation efforts, showing that it is not just about increasing population size, but also about actively monitoring genomic health.

The mystery of the mammoths

The team did not include genomes from the last 300 years of mammoth existence in their study. However, they plan to sequence fossils from this period to better understand the extinction event.

“What happened at the end is still a bit of a mystery – we don’t know why they disappeared after being more or less fine for 6,000 years, but we think it was something unexpected,” Dalén said. “I would say there is still hope of understanding why they disappeared, but no promises.”

The study is published in the journal Cell.

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