Sunday, June 29, 2008

The viking heritage

Given the fact that I live in a country that glorifies its viking past, I can't help be surprised that I had totally overlooked this paper published in PLoS One in May.

Evidence of Authentic DNA from Danish Viking Age Skeletons Untouched by Humans for 1,000 Years by Linea Melchior et al

I'm sure it has been reported somewhere in the Danish press, but I'm also sure that the focus of such coverage has been entirely wrong.

What's interesting about the PLoS One paper is not that it's viking DNA that they retrieved, that's just an artifact of the fact that the research happened in Denmark, but rather the fact that the DNA was retrieved from a 1000 year old skeleton.

Of course, to get the correct DNA, the sampling required quite a bit of care, to avoid contamination. As the abstract clearly describes.

Background

Given the relative abundance of modern human DNA and the inherent impossibility for incontestable proof of authenticity, results obtained on ancient human DNA have often been questioned. The widely accepted rules regarding ancient DNA work mainly affect laboratory procedures, however, pre-laboratory contamination occurring during excavation and archaeological-/anthropological handling of human remains as well as rapid degradation of authentic DNA after excavation are major obstacles.

Methodology/Principal Findings

We avoided some of these obstacles by analyzing DNA from ten Viking Age subjects that at the time of sampling were untouched by humans for 1,000 years. We removed teeth from the subjects prior to handling by archaeologists and anthropologists using protective equipment. An additional tooth was removed after standard archaeological and anthropological handling. All pre-PCR work was carried out in a “clean- laboratory” dedicated solely to ancient DNA work. Mitochondrial DNA was extracted and overlapping fragments spanning the HVR-1 region as well as diagnostic sites in the coding region were PCR amplified, cloned and sequenced. Consistent results were obtained with the “unhandled” teeth and there was no indication of contamination, while the latter was the case with half of the “handled” teeth. The results allowed the unequivocal assignment of a specific haplotype to each of the subjects, all haplotypes being compatible in their character states with a phylogenetic tree drawn from present day European populations. Several of the haplotypes are either infrequent or have not been observed in modern Scandinavians. The observation of haplogroup I in the present study (<2% in modern Scandinavians) supports our previous findings of a pronounced frequency of this haplogroup in Viking and Iron Age Danes.

Conclusion

The present work provides further evidence that retrieval of ancient human DNA is a possible task provided adequate precautions are taken and well-considered sampling is applied.


This is rather existing news, since it means it's possible to get decent DNA samples from even millennium old human remains, if they are just handled correctly before and during sampling. This will help us gain better insight of our ancestors, and recent human evolution.

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