Stephan C. Schuster and Webb Miller of Penn State, working with Thomas Gilbert from Copenhagen and a large international consortium, discovered that hair shafts provide an ideal source of ancient DNA -- a better source than bones and muscle for studying the genome sequences of extinct animals. Their research achievement, described in a paper to be published in the journal Science on Sept. 28, includes the sequencing of entire mitochondrial genomes from 10 individual woolly mammoths.
Before this study, only seven mitochondrial genomes from extinct animals had been published: four from ancient birds, two from mammoths and one from a mastodon.
"DNA in bones and muscle usually degrades and becomes contaminated with genetic material from other sources such as bacteria, limiting its usefulness in scientific studies," Schuster explained. Because only a tiny proportion of ancient bones and muscle are preserved in such a way that uncontaminated DNA can be recovered, research with such materials has involved laborious efforts, sometimes spanning as long as six years for a single study. In contrast, Miller said, "Once I get the data from the genome sequencer, it takes only five minutes to assemble the entire mitochondrial genome."
"We realized that the keratin in hair could protect the DNA it contains from outside influences and hence from the sorts of degradation that affect DNA in other parts of the body, such as bone," Gilbert said. Hair also can more easily be cleaned of environmental contaminants, such as bacteria. The researchers discovered that, even if the hair is washed in a solution that kills and washes off external DNA, the genetic material within the hair is unaffected.
This technique opens up the possibility of recovering lots more information about the genetics of extinct species, such as their relationship to other species, as well as population dynamics within a given species, which could answer important questions about extinction and survival during times of shifting climate.
In a sad turn of events, publishing this genetic data led to three of the ten mammoths losing their health insurance after their carriers determined that they might be at risk of developing potentially expensive medical conditions later in life.
(Thanks to Coturnix for pointing this one out.)