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New DNA Technique Helps Trace Evolution of Mammoths

December 24, 2005|Thomas H. Maugh II | Times Staff Writer

A new sequencing technique has enabled researchers to decipher 1% of the genetic blueprint of the long-extinct woolly mammoth, the largest fragment of DNA ever decoded from a fossilized species.

The results show that the creatures diverged from African elephants 6 million years ago and from Asian elephants a relatively short 440,000 years later.

The feat suggests it could be possible to decipher the entire mammoth genome and clone the creatures.

The mammoths, which were about the size of modern Indian elephants, roamed the grassy plains of the Northern Hemisphere until they died out almost entirely about 10,000 years ago because of hunting by humans, the changing climate and, perhaps, disease. A small pocket of the animals persisted on a Siberian island until about 3,500 years ago.

Explorers have found about 100 mammoth corpses frozen in Siberia, many in a remarkable state of preservation. Several are in the Mammoth Museum in Khatanga, Russia, where a team from McMaster University in Canada and Pennsylvania State University extracted DNA from the jawbone of a 28,000-year-old female.

The team, reporting in the current issue of the journal Science, was able to sequence about 13 million base pairs from the mammoth genome. They found the DNA segment was 98.5% identical to a similar segment from modern African elephants.

With sufficient funding, said Penn State geneticist Steven C. Schuster, the team could do another 1% of the genome each day.

In a second paper, published in the journal Nature, a team from the Max Planck Institute for Evolutionary Anthropology in Germany reported they had sequenced mitochondrial DNA from the same mammoth. Mitochondrial DNA, which is transmitted from mother to child in small organelles within cells, accounts for only about 0.0006% of the mammoth's total DNA but is much easier to work with.

Their results on mammoth evolution were the same as those reported by the first group.

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