I was recently caught a bit on my heels, by news of the Neanderthal Genome Project, in part as Paleo is not my forte. With all the problems involved I had no idea anyone would even attempt this type of project. For those unfamiliar with this topic I’ve provided some background information as posted on Wikipedia, with very minor edits. This tread questions the fact and fiction surrounding the results and science of this project.
Introduction:
In July 2006, the Max Planck Institute for Evolutionary Anthropology and 454 Life Sciences announced that they would be sequencing the Neanderthal genome over the next two years. At three billion base pairs, the Neanderthal genome is roughly the size of the modern human genome; according to preliminary sequences, modern human and Neanderthal DNA appear to be 99.5% percent identical. (To put this into context, note that chimpanzee DNA is 98.77% identical to human DNA.)
The researchers recovered Neanderthal DNA by extracting all the DNA from the femur bone of a 38,000-year-old male Neanderthal specimen from Vindija Cave, Croatia. Two different research teams working on the same Neanderthal sample have published their results, Nature and Science. The results have been received with a fiery polemic, mainly surrounding the issue of a possible Neanderthal admixture to the modern human genome.
Project Results:
One group used a new sequencing technique that amplifies single molecules for characterization and obtained over a quarter-million unique sequences. Co-author Svante Pääbo directly sequenced the Neanderthal nuclear DNA genome. Since direct sequencing is random, one must wait for specific sequences for genes that might be different between modern humans and Neanderthals to show in the process. Direct sequencing destroys the original sample, so in principle the metagenomic library approach will forever retain a clone of the Neanderthal DNA for future targeted research.
The second group used a different technique, one in which the Neanderthal DNA is inserted into bacteria, which make multiple copies of a single fragment. It's a slower technique and only 65,000 bases were sequenced, but the same DNA can be obtained from the bacteria as needed and thus allows for a higher degree of error correction. They demonstrated that Neanderthal genomic sequences can be recovered using a metagenomic library-based approach. All of the DNA in the sample is "immortalized" into metagenomic libraries. A DNA fragment is selected, then propagated in microbes. The Neanderthal DNA can be sequenced or specific sequences can be studied.
Overall, their results were remarkably similar. One group suggested there was a hint of mixing between human and Neanderthal genomes, while the other found none, but both recognize that the data set is just not large enough to give a definitive answer. The publication revealed Neanderthal DNA sequences matching chimpanzee DNA but not modern human DNA at multiple locations, thus enabling the first accurate calculation of the date of the most recent common ancestor of H. sapiens and H. neanderthalensis. The research team estimates the most recent common ancestor of their H. neanderthalensis samples and their H. sapiens reference sequence lived 706,000 (divergence time), estimating the separation of the human and Neanderthal ancestral populations to 370,000 years ago (split time).
Earlier mitochondrial DNA research led by Svante Pääbo in 1997 had indicated archaic Homo sapiens and Neanderthals broke into separate lineages approximately 500,000 years ago (split time). One of the current teams calculated a divergence time of 516,000 years ago and don't indicate a split, while they claim the average divergence time between alleles within humans is thus 459,000 years with a 95% confidence interval between 419,000 and 498,000 years: "Neanderthal genetic differences to humans must therefore be interpreted within the context of human diversity." On the other hand, the other team found no evidence of Neanderthal admixture to the modern human genome, but they cannot preclude admixture of up to 20% with a certainty better than 95%, and hence do not claim to present a definite answer to the question.
The location of sites where the physical remains
of Neanderthals have been recovered.
Cheers
CmacQ
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Source: Wikipedia (Neanderthal genome project 07-22-08)
Important note: Both teams that conducted the current research project and the 1997 study used materials from the same individual sample.
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