Sept. 4, 2008 -- DNA shows the world's last surviving woolly mammoths were born in the United States and the Arctic. Woolly mammoths from those regions displaced Siberian mammoths, causing the latter group to mysteriously disappear off the face of the Earth.
The findings, published in the latest Current Biology, are based on the largest study ever conducted on DNA extracted from woolly mammoths, which grew tusks up to 16 feet long and had enormous, elephantine bodies.
The paper, which focused on mitochondrial DNA (mtDNA) -- genetic material inherited from mothers -- is also the second largest study to date for any ancient DNA.
Although North American and Siberian woolly mammoths shared a common ancestor around 900,000 years ago, the two groups went their separate ways for thousands of years, until the first group started to move back into Siberia between 100,000 to 50,000 years ago.
"Whether the (North American) mammoths were better suited to the environment or the (local) population simply dwindled due to other reasons is unknown, but I would not be surprised if the North American mammoth immigrants were partly to blame," coauthor Hendrik Poinar told Discovery News.
Poinar, a McMaster University anthropologist, and his international team analyzed mtDNA from 160 mammoth samples from Holarctica, the term for the region that now includes Asia, Europe and North America. The scientists made three other key discoveries about mammoths.
The first is that two different species of mammoths might have both lived in Siberia at one point. The second species could have been a more primitive form, such as Trongotherii or Meriodonalis.
The scientists also determined that the Bering Land Bridge, which joined Alaska to eastern Siberia, was more of a barrier than a gateway.
"I think it is increasingly clear that the bridge was indeed a filter more than a bridge," Poinar said. "It certainly was not a freeway, and it makes us think about what ecological function it clearly played over the last several millennia."
He explained that only four or five mammoth migration events took place over the bridge during a period of tens of thousands of years.
The scientists also ruled out the popular theory that climate change played a direct role in the mammoth's extinction, since the mammoths "sailed through The Last Glacial Maximum (the time of maximum extent of the ice sheets) with little effect on their overall diversity."
The woolly mammoth populations on mainland North America and Siberia did not die out until 9,800 to 11,000 years ago. Much smaller populations, on Wrangel Island off the coast of Siberia and the Pribilof Islands off Alaska lived on until 3,500 to 5,000 years ago.
Poinar admits that climate probably played some role in the mammoth's demise but, he adds, "I cannot buy that humans did not have a hand in (the extinction) as well."
Jim Mead, professor and chair of East Tennessee State University's Department of Geosciences, told Discovery News that the new study "is very interesting."
"It certainly indicates that we all must look to other models about the various megafaunal populations in the Holarctice," Mead said, adding that, "it is intriguing that the mammoth mirrors that of bison and other megamammals."
Bison, mammoths, early relatives of bears, horses and other large mammals all experiencd population expansions and reductions at similar times. This suggests that climate change was affecting these groups, humans were hunting them more, or perhaps both climate and a human fondness for meat together affected these ancient animals.
Related Links:
Discovery News blog: Born Animal
our sites
video
mobile
shop
stay connected
corporate
