Washington, Nov 20 : Scientists at Penn State have for the first time sequenced the genome of the woolly mammoth, an extinct species of elephant that was adapted to living in the cold environment of the northern hemisphere. ccording to Webb Miller, professor of biology and of computer science and engineering and one of the project's two leaders, the scientists are the first to report the genome-wide sequence of an extinct animal.
They sequenced four billion DNA bases using next-generation DNA-sequencing instruments and a novel approach that reads ancient DNA highly efficiently.
Although their dataset consists of more than four-billion DNA bases, only 3.3 billion of them can currently be assigned to the mammoth genome.
Some of the remaining DNA bases may belong to the mammoth, but others could belong to other organisms, like bacteria and fungi, from the surrounding environment that had contaminated the sample.
The team used a draft version of the African elephant's genome, which currently is being generated by scientists at the Broad Institute of MIT and Harvard, to distinguish those sequences that truly belong to the mammoth from possible contaminants.
The team sequenced the mammoth's nuclear genome using DNA extracted from the hairs of a mammoth mummy that had been buried in the Siberian permafrost for 20,000 years and a second mammoth mummy that is at least 60,000-years-old.
The research yielded information about the evolution of the three known elephant species: the modern-day African and Indian elephants and the woolly mammoth.
The team found that woolly mammoths separated into two groups around two million years ago, and that these groups eventually became genetically distinct sub-populations.
They also found that one of these sub-populations went extinct approximately 45,000 years ago, while another lived until after the last ice age, about 10,000 years ago.
In addition, the team showed that woolly mammoths are more closely related to modern-day elephants than previously was believed.
"Our data suggest that mammoths and modern-day elephants separated around six-million years ago, about the same time that humans and chimpanzees separated," said Miller.
"However, unlike humans and chimpanzees, which relatively rapidly evolved into two distinct species, mammoths and elephants evolved at a more gradual pace," said Stephan C. Schuster, Penn State professor of biochemistry and molecular biology and the project's other leader.
According to Schuster, the data will help to shed light on the rate at which mammalian genomes, in general, can evolve.
"This really is the first time that we have been able to study an extinct animal in the same detail as the ones living in our own time," said Schuster.