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[ Text by Darren Platt of the Joint Genome Institute ]
After 50,000 years the DNA fragments are understandably much shorter we are lucky to get a 70 base pair fragment. Using the method described in our paper we actually cloned these fragments and were therefore able to sequence them multiple times. You can see on the screen shot the reads actually stack up on top of one another and you can see forward and reverse reads on the same fragment, all starting in very similar positions. This is one of several ways we can be sure it's ancient DNA. If it was modern human DNA the fragments would be much longer