The last stock of woolly mammoths suffered from harmful mutations for thousands of years – but it was not why they became extinct, a new study shows.
The finding is still bad news for species that are threatened today, says Professor Love Dalén.
Why did the mammoths die out? The question has puzzled researchers for eternity, and now at least the theory that they died from mutations can be dismissed, according to a new study published in the scientific journal Cell.
The study, conducted at the Centre for Palaeogenetics in Stockholm, has clarified DNA from 21 mammoths to investigate how the gene pool is affected by sudden population declines.
The last stock on Wrangel Island was close to extinction, but quickly recovered to around 300 reproducing individuals and maintained that number until they suddenly disappeared, says Love Dalén, professor of evolutionary genomics and one of the researchers behind the study.
Our analyses show that they were afflicted with genetic diseases for thousands of years due to this bottleneck.
No Competition
The study concludes that it did not lead to the mammoths' extinction. But it does not mean that today's threatened species will overcome mutations created by population declines in the same way, according to Dalén.
For the mammoths' part, there were, for example, no humans or competitors that could have had a negative impact. It was only mammoths and lemmings on this island.
Dalén believes that the results of the study are valuable even today.
If you take a step back, you can draw conclusions about what will happen to today's threatened species. At a genetic level, all mammals function in the same way.
He mentions the Swedish Arctic fox as an example.
They were about 20 individuals 25 years ago. Today, we have, through extensive measures, managed to increase the number to a few hundred, but we should probably count on them being affected by inbreeding depression for several generations to come, he says.
It's not certain that the Arctic fox will cope with this as well as the mammoth. It's bad news.
Move Individuals
To reduce the risk of extinction, other measures may be needed.
We can, for example, move individuals between different populations and thereby break inbreeding. If we take the Swedish Arctic fox as an example, we can try to get Arctic foxes from Siberia.
Will we continue to live with the joke that the mammoths died out because there were no papputars?
I would say that there is a 50 per cent chance that the answer is correct. Precisely at the end, there must have been either a male or a female left, says Dalén.
