Reconstruction of genomic DNA sequence of extinct species is a daunting task. Scientists who were trying to achieve this goal had faced various difficulties. U.S. Department of Energy (DOE) Joint Genome Institute (JGI) researchers overcame a number of of the difficulties normally associated with recovery of DNA from old samples. Samples of DNA would start degrading at death of the animals and is flooded by various microorganisms. These microbes attack the decaying carcass to utilize the nutrients present in the dead organism as an energy source. What remains and confounds the efforts to sequence and characterize these artifacts is an overabundance of microbial contaminants along with the occasional DNA fingerprints contributed unwittingly by the modern fossil hunters or lab workers.

The genomic DNA sequencing of an extinct Pleistocene cave bear species has been logged into scientific literature thanks to researchers from the U.S. Department of Energy (DOE) Joint Genome Institute (JGI). This study, reported in the latest issue of online edition of the journal Science, has set the research community's sights on traveling back in time through the vehicle of DNA sequencing to reveal the story of other extinct species, including our nearest relatives, the Neanderthals.

"Among the limitations of prior ancient DNA studies was that they were restricted to mitochondrial DNA sequences," said Eddy Rubin, who is the DOE JGI director. "While mitochondria are great for learning about evolutionary relationships between species, to understand the functional differences between extinct and modern species we really need genomic DNA, and nobody has been able to purify and sequence large quantities of DNA from these old samples." The work was done in Rubin's laboratory.