Interspecies Breeding Influenced Evolution Of Mammoths, DNA Study Reveals
It appears that mammoths had plenty of interspecies sex, according to a new study.
It had been fairly established that different mammoth species roamed the North American continent, such as the massive Columbian mammoth and the pony-sized pygmy mammoth. But this new research suggested that these creatures were likely to be interbreeding, which then influenced their evolution.
Scientists traditionally divided these animals into species based on tooth and bone differences. The boundaries among species, however, remain quite tricky, according to lead study author Hendrik Poinar, professor at Canada’s McMaster University.
“[O]ther features may not correspond to those boundaries, suggesting that what we formerly regarded as separate species are in fact not at all," said Poinar, whose team then turned to and found clues in mammoth DNA.
Extracting DNA from samples of fossilized bone, teeth and feces of 67 specimens, the researchers discovered that while Columbian, woolly and pygmy mammoths looked different, entered North America at varying periods and lived in separate environments, they had surprisingly similar DNA.
These findings support the notion that all North American mammoths could have hailed from a single primitive species – the steppe mammoth – through an openness to interbreed.
Most striking was the case of the Columbian and woolly mammoths, which seemed distinct based on their molar teeth but weren’t really genetically separate. The former, a largely hairless one, is thought to arrive in the continent 750,000 to 1 million years before the latter.
Many species showed some Columbian and woolly traits while others, such as the Jefferson’s mammoth, exhibited qualities that are halfway in between. The pygmy mammoth was least closely related to the other species, a suggestion that it most resembled the steppe ones.
"[W]e suspect that subgroups of mammoths evolved to deal with local conditions, but maintained genetic continuity by encountering and potentially interbreeding with each other where their two different habitats met, such as at the edge of glaciers and ice sheets,” explained Poinar.
So despite differences that evolved in their physical appearance in order to survive in different settings, mammoths still interbred and produced healthy offspring when they met back up. At any rate, they maintained unique adaptive characteristics based on where they survived.
"You throw a Columbian up in the far north in the middle of winter at -80 and he's not surviving. You take a woolly and throw him down into the Everglades and he's sweating to death,” Poinar said.
The team is counting on advances in extracting and studying ancient DNA to break down walls in understanding evolutionary history. The case of mammoths, for instance, is considered similar to what paleontologists found with human species and Neanderthals – different skeletally yet linked through swapped genetic material.
And the idea of them being a single creature showing evolutionary responses to various landscapes, according to paleontologist Chris Widga of the Illinois State Museum, expands the sample size for analyzing how animal populations “become tuned” to separate ecological systems. This lends insight not only where mammoths came from, but also how such flexible species became extinct 10,000 years ago.
The findings were published in the journal Frontiers in Ecology and Evolution.
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