Thursday, January 18, 2007

Extracting DNA From Fossils

Freshly excavated fossil bones are best for amplification of ancient DNA. 2007. M. Pruvost et al. PNAS 104 : 739-744.
DNA preserved in bones undergoing fossilization deteriorates up to 50 times faster when stored in a museum than when the bones are buried in the ground.
This study shows that in order to improve the quality of paleogenetic analyses, archeological and paleontological remains should be treated like biological samples both during and after excavation.

An extensive study of around 250 fossil bones from 600 to 50 000 year old herbivores showed that mitochondrial DNA from freshly excavated, untreated fossil bones was amplified with a success rate of 46%. However, the rate is a mere 18% for fossil bones from collections which have been washed, dried and stored.

These findings were confirmed by a study on fossil bones from a single animal, an aurochs which became buried 3 200 years ago in the Sarthe region of France. The fossil bones were excavated during two excavation campaigns, the first carried out in 1947, and the second in 2004. None of the fossil bones excavated in 1947 and stored in the Musée Vert yielded any results from paleogenetic analysis. On the other hand, DNA amplification was obtained with all the 2004 fossil bones, thus yielding significant results from paleogenetic analysis.

Another finding revealed by this study was that the DNA had deteriorated as much in 57 years as during the previous two thousand years of burial. link