Washington, September 5 : A DNA-based study has revealed that the last of the woolly mammoths, which lived between 40,000 and 4,000 years ago, had roots that were exclusively North American.
"Scientists have always thought that because mammoths roamed such a huge territory-from Western Europe to Central North America-that North American woolly mammoths were a sideshow of no particular significance to the evolution of the species," said Hendrik Poinar, associate professor in the departments of Anthropology, and Pathology and Molecular Medicine at McMaster University.
Poinar and Regis Debruyne, a postdoctoral research fellow in Poinar's lab, spent the last three years collecting and sampling mammoths over much of their former range in Siberia and North America, extracting DNA and meticulously piecing together, comparing and overlapping hundreds of mammoth specimen using the second largest ancient DNA dataset available.
"Migrations over Beringia (the land bridge that once spanned the Bering Strait) were rare; it served as a filter to keep eastern and western groups or populations of woollies apart," said Poinar.
"However, it now appears that mammoths established themselves in North America much earlier than presumed, then migrated back to Siberia, and eventually replaced all pre-existing haplotypes of mammoths," he added.
According to Ross MacPhee, curator of mammalogy at the American Museum of Natural History, and one of the researchers on the study, "Small-scale population replacements, as we call them, are not a rare phenomenon within species, but ones occurring on a continental scale certainly are."
"We never expected that there might have been a complete overturn in woolly mammoths, but this is the sort of discoveries that are being made using ancient DNA. Bones and teeth are not always sensitive guides," she added.
Like paleontologists, molecular biologists have long been operating under a geographic bias.
"For more than a century, any discussion on the woolly mammoth has primarily focused on the well-studied Eurasian mammoths," said Debruyne.
"Little attention was dedicated to the North American samples, and it was generally assumed their contribution to the evolutionary history of the species was negligible. This study certainly proves otherwise," he added.
"The study of evolution is an evolution in itself. This latest research shows we're drilling down and getting a closer and better understanding of the origins of life on our planet," said Poinar.