Did Neanderthals Interbreed With Homo-Sapiens?
Neanderthal Fossil Raises Questions about Human Origins
Sep 28, 2008
For the very first time anywhere, Richard Green and his team at the Max-Planck Institute for Evolutionary Anthropology in Germany have been able to sequence the complete mitochondrial genome of a Neanderthal.
This is also the first time a complete mitochondrial genome has ever been extracted from the fossil of an extinct hominid.
Mitochondria have their own DNA, including 13 protein-coding genes, and are inherited from the mother`s side. The Neanderthal genome was sequenced 35 times to ensure its accuracy.
What the researchers found by studying the genome, is that Neanderthal mitochondria falls outside of the range of variation found in modern humans, a discovery that suggests they did not contribute to our genetic make-up today.
Green and his team were still careful to point out that this does not mean that interbreeding between Neanderthals and humans would have been impossible.
Previous work done to establish the genetic distance between chimpanzees and humans established that they diverged evolutionarily six to eight million years ago.
This finding allowed researchers to measure the changes in mtDNA sequences since that time for both Neanderthals and humans, and to establish that the last time Neanderthals and humans shared a common ancestor was between 800,000 and 520,000 years ago, a creature something like Homo-Erectus, a hominid known for both its brains and its brawn.
Green’s team has gathered from studying the DNA that the Neanderthal population must have at one point shrunk to as low as just a few thousand individuals. They can glean this from how little purification acted upon the Neanderthal's DNA 40,000 years-ago.
Even more surprising is how much genetic change through certain amino acid substitutions has occurred in the human population since the human/Neanderthal split.
The team has already begun to sequence the entire Neanderthal nuclear genome, and expect to be finished by the end of the year.
Only then will we know conclusively if Neanderthals did contribute to the modern human gene-pool, or if they ultimately left this earth to their close human cousins.
Sources
Jennifer Viegas, “Neanderthal Bone Yields Complete Mitochondrial Genome”, Discovery News, Aug. 7, 2008
Ker Than, “Neanderthals Didn't Mate With Modern Humans, Study Says”, National Geographic News, August 12, 2008
Richard E. Green, Anna-Sapfo Malaspinas, Johannes Krause, Adrian W. Briggs, Philip L.F. Johnson, Caroline Uhler, Matthias Meyer, Jeffrey M. Good, Tomislav Maricic, Udo Stenzel, Kay Prüfer, Michael Siebauer, Hernán A. Burbano, Michael Ronan, Jonathan M. Rothberg, Michael Egholm, Pavao Rudan, Dejana Brajkovic, Ċ½eljko Kucan, Ivan Gušic, Mårten Wikström, Liisa Laakkonen, Janet Kelso, Montgomery Slatkin, and Svante Pääbo, “A Complete Neandertal Mitochondrial Genome Sequence Determined by High-Throughput Sequencing”, Cell, Aug. 22, 2008
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