Last updated February 27, 2018 at 11:18 am
An international team of researchers has finally worked out the evolutionary relationships of elephants and their ancestors.
Large bull elephants gather to drink in Tsavo National Park, Kenya. Credit: iStock
The researchers analysed 14 complete elephant genomes, from the three modern species of elephants, and 11 extinct species including mastadons, woolly mammoths, Columbian mammoths and the largest elephant ever to walk the earth – Palaeoloxodon which lived about 120,000 years ago.
Ancient elephants interbred with each other
“Elephants and their ancient relatives like the woolly mammoths and mastodons have long fascinated people the world over. But until now there has been no comprehensive assessment of their evolutionary relationships,” says Professor David Adelson, Director of the University of Adelaide’s Bioinformatics Hub, which sequenced the genomes.
“The most surprising result was the degree of interbreeding between species. We didn’t really expect there would be gene flow between the mammoths and mastodons and the ancestors of modern elephants, but our results showed frequent interbreeding,” he says.
“It’s really unique to be able to take steps back in time,” says Hendrik Poinar, evolutionary geneticist and one of the lead authors of the paper.
“Despite millions of years of separation, there was intermingling going on at many different levels. Biology is way messier than many people like to think.”
This interbreeding allowed elephants to be much more adaptable than many other mammals. Over the last million years elephants from the Americas and Europe were interbreeding, and it allowed them to adapt to environments from the arctic to the savannah, which helps explain why elephants have been so successful, at least until modern times where the remaining species are threatened from human poaching and environmental degradation.
Close up of a slice of bone from permafrost preserved Woolly Mammoth.
Credit: JD Howell, McMaster University
Three modern elephant species
The research confirmed previous work showing that modern elephants fall into three species, Asian elephants, and forest and savannah African elephants.
Surprisingly, there is no genetic evidence of interbreeding between the remaining three elephant species. Forest African elephants had the most genetic diversity of the remaining elephants, despite having the smallest population. The forest and savannah elephants have been distinct species for about 500,000 years.
Does this mean we could we bring back woolly mammoths?
Could we use a modern elephant as a surrogate for bringing back a woolly mammoth? This paper shows that there has been a lot of successful hybridisation in the past, so there probably wouldn’t be as many limitations to that from a physiological and biochemical point of view. But the research team would rather see efforts made elsewhere.
“What we see critically is that both Asian and African elephants are at abysmally low levels of genetic diversity and numbers in the wild,” says Hendrik Poinar.
“If efforts are really to try and save this phenomenal family, those efforts should be entirely focused on saving the contemporary populations of elephants. Those are the ones that need us.”
The paper was published in Proceedings of the National Academy of Sciences.
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