Thu, 06 May 2010 17:15 CDT
How closely are Neanderthals related to us?
© Javier Trueba/MSF/Science Photo Library
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They are so closely related that some researchers group them and us as a single species. "I would see them as a form of humans that are bit more different than humans are today, but not much," says Svante Pääbo, a palaeogeneticist at the Max Planck Institute in Leipzig, Germany, whose team sequenced the Neanderthal genome.
The common ancestor of humans and Neanderthals lived in Africa around half a million years ago. After that, the ancestors of Neanderthals moved north and eventually made it to Europe and Asia. Our ancestors, meanwhile, stuck around Africa until about 100,000 years ago before eventually conquering the globe. Neanderthals died out around 28,000 years ago.
How did they sequence the Neanderthal genome?
Bone contains DNA that survives long after an animal dies. Over time, though, strands of DNA break up, and microbes with their own DNA invade the bone. Pääbo's team found ways around both problems with 38,000 and 44,000-year-old bones recovered in Croatia: they used a DNA sequencing machine that rapidly decodes short strands and came up with ways to get rid of the microbial contamination.
They ended up with short stretches of DNA code that computers stitched into a more complete sequence. This process isn't perfect: Pääbo's team decoded about 5.3 billion letters of Neanderthal DNA, but much of this is duplicates, because - assuming it's the same size as the human genome - the actual Neanderthal genome is only about 3 billion letters long. More than a third of the genome remains unsequenced. "It's pretty darn good for something that's 38,000 years old," says Edward Green, a team member now at the University of California, Santa Cruz.