Scientists have sequenced the genome of Neanderthals, the closest relatives of modern humans. The initial analysis, published in this week’s Science magazine, showed that up to 2 percent of the modern human’s DNA outside of Africa came from Neanderthals or in Neanderthals’ ancestor.
Neanderthals and modern human shared a common ancestor about 500,000 years ago. Neanderthals lived in parts of Europe and western Asia and became extinct 30,000 years ago. In addition, Neanderthals and the modern human shared the space possibly as early as 80,000 years ago. One of the interesting and controversial questions around for a while is that did the modern humans and the Neanderthals mate?
Neanderthal Genome Sequence Project
An international team of scientists led by Svaante Paabo, sequenced the genome of three Neanderthal females who lived 40,000 years ago. The scientists have produced the first draft of Neanderthal genome sequence containing more than 3 billion letters of DNA.
A major challenge in sequencing the Neanderthal genome is the risk of contamination from moder human as the genomes of Neanderthal and modern human are ~99.8% identical. Novel techniques and the development of high-throughput DNA sequencing technologies have made the sequencing of ancient DNA possible and Svaante paabo is a pioneer in sequencing DNA from extinct species.
Till recently we could only compare the fossilized specimens of Neanderthals with human in a qualitative manner. With the first draft of complete genome sequence of Neanderthal genome, we are in a much better position to understand “what makes us human?”.
Evidence of Inter-breeding of Modern Human and Neanderthals
To compare how Neanderthal genome sequence differ from the modern human, the team sequenced five human living in France, China, southern Africa, western Africa and Papua New Guinea. The comparison of Neanderthal genome with modern human genomes showed that the Neanderthal genome is more similar to people from outside Africa than the people from Africa. The comparative analyses showed a clear evidence of low level of interbreeding. The lead author Svante Pääbo said,
In a sense, the Neanderthals are then not altogether extinct. They live on in some of us.
In addition, the results show that there has been gene flow from Neanderthals into the people lived in Europe and Asia, but not the people who lived in Africa. This suggests that Neanderthals probably interbred with early modern humans before Homo sapiens split into different groups in Europe and Asia.
Scientists could achieve the major feat of sequencing the extinct Neanderthal genome in just about 10 years after the sequencing the first human genome. The sequencing of extinct human species has opened a number of new avenues of research and it has huge implications to understand the history modern humans.