Friday, May 7, 2010

What Makes Us Human? Decoding the Neandertal

It's no secret that the Homo sapiens species is unique amongst the animal kingdom. Our brains are highly complex, we've designed and used tools to do more than hunt and build shelter, we've created the iPad and Levi's... It can be easy to see our species as so unlike any other that we forget that there had to have been a time when maybe we weren't quite so special.

In today's issue of Science, Green et al. discuss how they have created a draft sequence of the Neandertal genome (3 different individuals) and compared it to modern humans from different parts of the world. The initial purpose was to try to identify what genome features, specifically, set modern humans apart from other hominids, like apes and Neandertals. But the result of the research turned out to be much more significant.

According to the study, humans and Neandertals coexisted in the Middle East approximately 80,000 years ago (after humans left Africa, but before they spread into Europe and Asia). It's been widely accepted for many years that the two species were distinct enough that interbreeding would not produce viable offspring. Apparently, we were wrong! The study results show that both Europeans and Asians share 1% to 4% of their genes with with Neandertals, but Africans share none -- suggesting that there was likely interbreeding between the two groups during this time.

The team's initial purpose of finding out what makes humans unique was fruitful, as well: "Even though the genomes of humans and Neandertals are 99.84% identical, the researchers identified regions that have changed or evolved since our ancestors and Neandertals diverged sometime between 270,000 and 440,000 years ago -- their new, slightly younger estimate of the split. So far, the team has detected tantalizing differences in genes involved in metabolism, skin, the skeleton, and the development of cognition, although no one knows yet how these genetic changes affect physiology."

This research has opened new doors to our understanding of the genealogy of human beings, and may very well provide us with clues as to why humans survived to modern day, while Neandertals did not. Visit the Science website to see supplementary materials, including podcasts, on this exciting new research.

For more information on heredity and genetics, see our modules on DNA and genetics in the Visionlearning Biology library.

Images used in this posting come from Tomislav Maricic, Chris Stringer AND Ofer Bar-Yosef, as used in Science.

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