Ancient DNA preserved in permafrost

I just read a post on the blog Laelaps on the extinction of mammoths and horses in the Alaskan interior. The discussion refers to this paper, which I haven't read yet but will hopefully get around to it soon. Instead of looking for fossilized hard tissues (bones, teeth), the researchers instead recovered mitochondrial DNA (mtDNA) from the permafrost (in this form, it's known as sedimentary ancient DNA, or sedaDNA). Conditions for fossilization of bones are rare, and thus once a species becomes rare the likelihood of an individual becoming fossilized is low. However, these animals still bleed, urinate, defecate, shed hair, etc, and these activities are not rare (indeed, they occur daily). Thus, it may be easier to pinpoint a more exact timeline for extinction using these methods.

I'm not going to reiterate what's in the blog, so if you're interested in the subject just click on the link above. I will, however, add that global climate change poses a great threat to this type of research in the future. Permafrost is by far the best environment to find sedaDNA, but once it melts and the meltwater leaches through the soil that DNA will be lost forever. It's tragic, as this is an incredibly fascinating (not to mention informative) technique, and I hope that emphasis is placed on funding additional expeditions sooner rather than later. Information on different species and from different sites would be an extremely useful tool in piecing together the natural prehistory of the Pleistocene megafauna (possibly even shedding light on the cause of the extinction event).


References:

Haile, J., Froese, D., MacPhee, R., Roberts, R., Arnold, L., Reyes, A., Rasmussen, M., Nielsen, R., Brook, B., Robinson, S., Demuro, M., Gilbert, M., Munch, K., Austin, J., Cooper, A., Barnes, I., Moller, P., & Willerslev, E. (2009). Ancient DNA reveals late survival of mammoth and horse in interior Alaska Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0912510106