Sep 28, 2007
An international research team says the process should work on other extinct animals, allowing their genetics to be studied in detail for the first time.
The mammoth DNA was taken from the hair shaft which was long thought to be a poor source for the "life molecule".
But the group tells Science magazine that the shaft's keratin material slows degradation and limits contamination.
"The idea has been that all the DNA is in the root and that the shaft is DNA-void, or of much lower quality," explained co-worker Dr Tom Gilbert from the University of Copenhagen, Denmark.
"This is why when we screened a whole load of mammoths, we thought we might be lucky if we took enough hair from one of them. Basically, for every mammoth we tried, it worked. That blew us away," he told the BBC.
The traditional route to DNA in ancient samples is through bones and preserved muscle, but any genetic material usually falls apart very soon after death and is prone to contamination from bacteria.
Having a new route to large quantities of well-preserved DNA should be a real boon to scientific research, Gilbert and colleagues say.
The team read the DNA using an established technology known as "sequencing-by-synthesis" - but its application to hair in the context of ancient samples is novel.
"The reason we think hair is so great comes down to the fact that as a structure, hair is made out of this material called keratin," explained Dr Gilbert, who works out of Copenhagen's Center for Ancient Genetics.
"It's a kind of protein that in a very simplistic sense can be viewed as a plastic that the DNA gets embedded in and surrounded by and protected by."
The scientists think the approach will also work for other items built from the durable protein, such as horns, nails, antlers, hooves and even feathers.
They say museum collections must hold countless specimens of recently extinct creatures from which researchers would love to get genetic information but had never bothered because they believed their DNA to be corrupted and beyond analysis.
Gilbert and colleagues targeted the mammoths' mitochondrial DNA, a special type of DNA frequently used to measure the genetic diversity of populations - how closely different groups of organisms are related to each other.
Where previously only two mammoth mitochondrial genomes had been published, the Science paper reports the production of 10 new ones, including one from the very first mammoth that was studied - the so-called Adams mammoth, which was found in 1799 and has been stored at room temperature for the last 200 years.
"From our experience working with old samples, the colder a sample has been preserved the better the quality of DNA. So, we're looking at permafrost animals -woolly rhino, for example.
"There are also a lot of old bison and horse mummies turning up in the permafrost. It's not just animals, there are humans [too]; there are a lot of mummies around the world with hair, ranging from Egypt, South America to the more cold, better-preserved ones in Greenland."
Asked the classic question about whether it would be possible to clone any extinct creatures back into existence, Dr Gilbert said that even if the full genetic sequence of a mammoth could be retrieved, the technology did not currently exist to turn that biochemical information into a live animal.