How the sex habits of mammoths and mastodons could help save modern elephants

Mammoths and mastodons, new research says, were successful in diverse environments and over such a large period of time because they were interbreeding – something the modern elephant isn't doing.

"The one main point is that elephant's history is messy and biology is messy. Elephants were hooking up with each other over long periods of time," evolutionary geneticist Hendrik Poinar told CBC News. 

Poinar is one of the senior authors on the paper and Director of the McMaster Ancient DNA Centre and principal investigator at the Michael G. DeGroote Institute for Infectious Research The new data suggests that with interbreeding, elephants were equipped to adapt to their environment much better than other organisms. 

An international team of researchers say they have produced one of the most comprehensive evolutionary pictures to date. The study was published Monday in the Proceedings of the National Academy of Science. The team included researchers from McMaster University, the Broad Institute of MIT and Harvard, Harvard Medical School, Uppsala University, and the University of Potsdam.

"As glaciers grew and contracted across the northern expanse of our lands here in Canada, the woollies who were living happy as pigs in feces up on the open tundra were probably pushed south into what we think of as the Midwest United States and the Great Lakes regions," Poinar speculated. "And there they meet up with Columbians. 

"It looks like the hotbed for mammoth dating was right around the Great Lakes, right around here," he said. "So Toronto was date night 12,000 years ago."

Elephants were hooking up with each other over long periods of time.- Hendrik Poinar

The researchers sequenced 14 genomes from several species – both living and extinct species from Asia and Africa, two American mastodons, a 120,000-year-old straight-tusked elephant and a Columbian mammoth.

Mammoths lived during the Pleistocene epoch several million years ago in Africa, Europe, Asia and North America, going extinct about 11,000 years ago. Mastodons appeared on Earth about 20 million years ago and roamed North America. They predate mammoths by millions of years, but died out about the same time as their larger cousins, both likely due to a combination of climate change and human hunting.

The scientists call it a very complicated history, characterized by widespread interbreeding. They say however, the behaviour has virtually stopped among living elephants, adding to fears about the future of the remaining species.  

A cry out for conservation

Poinar says the research is most likely the most relevant to elephant conservationists who will find it the useful in aiding conservation efforts.

Researchers didn't find genetic evidence of interbreeding among two of the world's three remaining species, the forest and savanna elephants.

This suggests that despite the elephants living in neighbouring habitats, they've lived in near-complete isolation for the past 500,000 years.

"There's been a simmering debate in the conservation communities about whether African savannah and forest elephants are two different species," said David Reich, another co-senior author at the Broad Institute who is also a professor at the Department of Genetics at Harvard Medical School (HMS) and a Howard Hughes Medical Institute investigator, in a press release.

"Our data show that these two species have been isolated for long periods of time – making each worthy of independent conservation status."

Poinar, who has been working on this research for the last decade, said "part of the reason species are adaptable was the ability to mix with each other and that provides them with the toolkit for adaptation. Now think about what we're slowly doing to the earth in terms of destroying habitats and species that used to interact with each other or overlap, are now no longer able to because we've put up a parking lot or some duplex system." 

This is one of the oldest high-quality genomes that currently exists for any species.-  Michael Hofreiter

Poinar says, if anything, this is a cry out for conservation, once again.

"What this means is that the adaptability of various species to the changing climate, which is a reality giving what we're doing to the climate as humans that unfortunately it's going to lead to more extinctions," said Poinar.

Interbreeding among mammoths

Poinar says the combined analysis of genome-wide data from all these ancient elephants and mastodons has raised the curtain on elephant population history.

Researchers say a detailed DNA analysis of the ancient straight-tusked elephant, for example, showed that it was a hybrid with portions of its genetic makeup stemming from an ancient African elephant, the woolly mammoth and present-day forest elephants.  

"This is one of the oldest high-quality genomes that currently exists for any species," said Michael Hofreiter at the University of Potsdam in Germany, a co-senior author who led the work on the straight-tusked elephant, in a press release.

Researchers also found further evidence of interbreeding among the Columbian and woolly mammoths, which was first reported by Poinar and his team in 2011. 

Despite their vastly different habitats and sizes, researchers believe the woolly mammoths, encountered Columbians mammoths at the boundary of glacial and in the more temperate areas of North America.