800 000 year old mammoth DNA modern elephant DNA or PCR artefact?

摘要

Poulakakis and colleagues (Poulakakis et al. 2006: Biol. Lett. >2, 451–454), report the recovery of ‘authentic’ mammoth DNA from an 800 000-year-old fragment of bone excavated on the island of Crete. In light of results from other ancient DNA studies that indicate how DNA survival is unlikely in samples, which are recovered from warm environments and are relatively old (e.g. more than 100 000 years), these findings come as a great surprise. Here, we show that problems exist with the methodological approaches used in the study. First, the nested PCR technique as reported is nonsensical—one of the second round ‘nested’ primers falls outside the amplicon of the first round PCR. More worryingly, the binding region of one of the first round primers (Elcytb320R) falls within the short 43 base pair reported mammoth sequence, specifically covering two of the three reportedly diagnostic Elephas polymorphisms. Finally, we demonstrate using a simple Blast search in GenBank that the claimed ‘uniquely derived character state’ for mammoths is in fact also found within modern elephants.