By Jennifer Green

A draft sequence of the Neanderthal genome has provided a new insight into evolution – including evidence of interbreeding with ‘modern day’ humans.
Scientists at the University of California in Santa Cruz sequenced the genome after extracting the necessary DNA from 40,000 year-old Neanderthal bones.

The results support the theory that early modern humans interbred with Neanderthals shortly after they migrated from Africa. Consequently sections of Neanderthal DNA will still be present in non-Africans living today.

Neanderthals coexisted with humans in Europe for thousands of years before they died out around 30,000 years ago.

Until recently, findings from fossils led some scientists to theorise that they interbred with Europeans, but the genome reveals a presence of a Neanderthal DNA signal in people from East Asia and Papua New Guinea – places Neanderthals never lived.

“The scenario is not what most people had envisioned,” said the paper’s first author, Richard Green. “We found the genetic signal of Neanderthals in all the non-African genomes, meaning that the admixture occurred early on, probably in the Middle East, and is shared with all descendants of the early humans who migrated out of Africa.”

Three billion nucleotides comprise the draft genome sequence, which was determined by analysing several Neanderthal bones, including three found in Vindiga Cave, Croatia.

The bones were so badly degraded that 95 per cent of the DNA extracted belonged to bacteria and other microorganisms. Consequently the scientists had to use special sequencing technology to extract the specific DNA.

Green admits the sequence is probably riddled with errors. Yet the team were able to compare it with human and chimpanzee genomes which enabled them to catalog genetic changes that are now present in a high frequency in modern humans.

“It sheds light on a critical time in human evolution since we diverged from Neanderthals,” Green said.

“What adaptive changes occurred in the past 300,000 years as we were becoming fully modern humans? That’s what I find most exciting. Right now we are still in the realm of identifying candidates for further study.”