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Mammoth discovery
Model mammoths in a Moscow museum (image courtesy of Ice Age Museum, Moscow/Fyodor Shidlovs)
In the 1993 film Jurassic Park, scientists recreated dinosaurs using DNA extracted from fossils. So far, this idea has remained science fiction. In actual fact, recovering ancient DNA is very difficult, even from animals that died thousands (rather than millions) of years ago. Genetic material in bones and muscle usually degrades and becomes contaminated by bacteria and other sources; the older the specimen, the less chance of recovering its DNA. Up to September 2007, only seven mitochondrial genomes from extinct animals have been published, four from ancient birds, two from mammoths and one from a mastodon (a distant relative of mammoths).
But now an international team of researchers led by Stephan C. Schuster and Webb Miller of The Pennsylvania State University have recovered and sequenced ancient DNA from an alternative source of genetic material: hair.
Schuster and Miller teamed up with Thomas Gilbert of the Center for Ancient Genetics at the University of Copenhagen and a large group of researchers and museum curators from the US, Russia, Belgium, Denmark, France, Italy, Sweden and the UK. The team obtained hair from ten woolly mammoths collected from a wide swathe of northern Siberia and with dates of death ranging from 12,000 to 50,000 years ago. One sample came from the so-called Adams mammoth. This mammoth died around 36,000 years ago; it was dug up in 1804-1806 and its hair has been stored in non-refrigerated museums for more than 200 years.
Despite the age of the specimens and the fact that some of them had been kept at room temperature for long periods, the team was able to isolate and sequence mitochondrial DNA from the shafts of the mammoth hairs. Hair shafts are rich in mitochondria, and the hair's keratin protects the mitochondrial DNA from degradation. As an added bonus, hair can be washed to remove external sources of contamination on the outside of the shaft.
Mitochondrial DNA is often used to examine the genetic diversity and evolutionary history of populations. Therefore, the new method will potentially enable these kinds of studies to be carried out on extinct species, including mammoths.
The researchers published their method and findings in the journal Science (September 28, 2007).
»Go to the abstract of the paper on the Science website
»Go to a press release about this research on the Eberly College of Science website