Mammoth DNA explains extinction

2008-11-20 11:09
Washington - Researchers have sequenced the gene map of a long-extinct, mummified woolly mammoth, using DNA taken from its hair.

The sequence shows that mammoths were more closely related to modern, living elephants than previously thought, and they found some elements, such as evidence of inbreeding, that may shed light on why the giant creatures went extinct, the researchers reported on Wednesday.

And it shows that it is possible to reconstruct the genomes of extinct creatures, they reported in the journal Nature.

"By deciphering this genome we could, in theory, generate data that one day may help other researchers to bring the woolly mammoth back to life by inserting the uniquely mammoth DNA sequences into the genome of the modern-day elephant," Stephan Schuster of Pennsylvania State University, who helped lead the research, said in a statement.

"This would allow scientists to retrieve the genetic information that was believed to have been lost when the mammoth died out, as well as to bring back an extinct species that modern humans have missed meeting by only a few thousand years."

Evolved slowly

The sequence shows that mammoths, which died out around 10 000 years ago, evolved slowly.

"We discovered that individual woolly mammoths were so genetically similar to one another that they may have been especially susceptible to being wiped out by a disease, by a change in the climate, or by humans," said Schuster.

The researchers will have to analyze the DNA to pinpoint some of the precise sequences unique to mammoths, but have some hints.

"Our data suggest that mammoths and modern-day elephants separated around six million years ago, about the same time that humans and chimpanzees separated," added Penn State biologist Webb Miller, who directed the study.

But mammoths and elephants appear more closely related than humans and chimpanzees are. Miller said the findings can help scientists understand evolution.

The researchers have been pulling DNA out of mummified mammoths and their hair for more than a decade, but because it is so old, the DNA is broken down. It is also contaminated by bacteria and fungi.

Mammoths offer a better target than most extinct animals because many of their bodies have been frozen since death - some so thoroughly that the meat is still edible.

The Penn State researchers believe they have about 80% of its genome complete.

Two groups

The evidence suggests that woolly mammoths then separated into two groups around 2 million years ago, which eventually became genetically distinct. One went extinct 45 000 years ago, while another survived until 10 000 years ago.

Next in line - perhaps Neanderthals, said Michael Hofreiter of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

"The next draft nuclear genome of an extinct species likely to become available is that of our closest relative, the Neanderthal, following on from publication of a complete Neanderthal mitochondrial genome sequence," Hofreiter wrote in a commentary.

A fast sequencing machine made by 454 Life Sciences, a Roche company, made the work possible, the researchers said. So far, 28 mammals have had their genomes sequenced, including humans, dogs, cats, rats and pigs.



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