A report appearing tomorrow in the journal Cell puts another nail in that theory’s coffin. Svante Paabo’s group at the Max Planck Institute for Anthropology in Germany has produced the first-ever complete sequence of a Neanderthal’s mitochondrial genome. Their analysis shows that the last common ancestor of humans and Neanderthals walked the Earth on the order of 660,000 years ago – hundreds of millennia earlier than the most recent common ancestor of all humans living today.
Mitochondrial DNA is passed down intact from mother to child. All people living today can use mitochondrial DNA to trace their maternal line back to the Mother of all Mothers (MoM), who probably lived about 175,000 years ago in eastern Africa.
When working with ancient DNA, researchers have to contend with several technical problems. Contamination by DNA from laboratory workers must be carefully avoided. And even if contamination is controlled, the inevitable chemical breakdown of DNA that has been buried for thousands of years can skew results. Lead author Richard Green and his colleagues avoided both of these pitfalls by sequencing the mitochondrial DNA nearly 35 times over.
“For the first time, we’ve built a sequence from ancient DNA that is essentially without error,” Green said in a statement.
The authors say that their success at sequencing the mitochondrial genome of a Neanderthal will help in their ultimate goal of sequencing the species’ much larger and more complicated nuclear genome, which could then be compared with a modern human genome to identify genes that were important in the emergence of Homo sapiens.