Wednesday, 18 February 2009

Neanderthals Part 3: Reconstruction of the Neanderthal Genome

by Kathryn Hadley

Do modern human beings descend from the Neanderthals? The question is subject to fierce debate and the Neanderthal is either categorised as a subspecies of humans (Homo sapiens neanderthalensis) or as a separate species (Homo neanderthalensis). Because Homo sapiens and Neanderthals coexisted for thousands of years, there has been speculation that they possibly interbred and that modern humans consequently inherited Neanderthal DNA in their genome. Results of the latest scientific studies of the DNA of the Neanderthals (notably explained in an article published by BBC News) have revealed, however, that they never interbred with the ancestors of modern human beings.

The latest research is led by Professor Svante Paabo from Germany's Max Planck Institute for Evolutionary Anthropology, who has sought to reconstruct a complete Neanderthal genome. He announced the first draft of the genome at the annual meeting of the American Association for the Advancement of Science, held in Chicago from February 12th - 16th. The reconstructed genome was based on genetic information uncovered from fossils of the bones of a Neanderthal man who died approximately 38,000 years ago, discovered in Vindija Cave in Croatia. A second team led by Edward Rubin of the US Department of Energy Joint Genome Institute and Lawrence Berkeley National Laboratory has also been working on the same samples using different technological strategies in an attempt to define the genome.

Paabo’s team has sequenced three billion ‘letters’, which are believed to cover almost 63% of the Neanderthal genome. Recent research has focused on the FOXP2 gene, which is associated with speech and language in modern human beings. Studies of the Neanderthal genome have confirmed that Neanderthals had the FOXP2 gene. Chimpanzees also have the FOXP2 gene, which differs from the human version of the gene at two key points, and the preliminary results of Paabo’s research appear to reveal that the FOXP2 gene in Neanderthals had the same variations. There are, however, too many different genes to conclude from these similarities that Neanderthals could not speak at all.

Above all, the reconstruction of the Neanderthal genome will provide a basis upon which to carry out further comparative studies with the human genome. In Paabo’s words, it will provide clues about the genetic regions that make us ‘uniquely human’.

‘Now that we have the Neanderthal genome, we can look for areas in the human
genome where a change seems to have swept rapidly through us since we separated
from Neanderthals. There, something special may have happened in us. The cool
thing is, now that we have the whole genome, we can look for these changes
without bias.’

Paabo confessed that he did not expect, however, to find any clues in the genome to help solve the mystery of their extinction:
‘I don't think they became extinct due to something in their genome. It was
clearly something in their interaction with the environment or with modern
humans that caused them to be extinct. That will not be something you can see
from their DNA sequence.’

An article about Paabo’s address at the annual meeting of the American Association for the Advancement of Science is available on their website
A presentation of the Draft Version of the Neanderthal Genome as well as a video of the press conference in which Paabo first announced the results of his research, in Leipzig on February 12th, is available on the website of the Max Planck Institute for Evolutionary Anthropology
A comprehensive article about the project is available on the site Archaeology

The current topicality of the Neanderthals is particularly timely in the light of the 200th anniversary of the birth of Charles Darwin and the 150th anniversary of the publication of his book On the Origin of Species, this year. For more information on the conflict between supporters of Darwin’s theory of evolution and creationists, read our article latest America's Difficulty with Darwin.

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