Were Neanderthals direct ancestors of contemporary humans or an evolutionary side branch that eventually died out?
This is one of the enduring questions in human evolution as scientists explore the relationship of fossil groups, such as Neanderthals, with people alive today.
The simultaneous publication of two studies with Neanderthal nuclear DNA sequences [1,2] was a technological breakthrough that held promise for answering a longstanding question in human evolution: Did “archaic” groups of humans, such as Neanderthals, make any substantial contribution to the extant human gene pool? The conclusions of the two studies, however, were puzzling and possibly contradictory.
Noonan and colleagues  estimated an older divergence time (i.e., time to the most recent common ancestor) between human and Neanderthal sequences (∼706,000 y ago), and a 0% contribution of Neanderthal DNA (95% confidence interval [CI]: 0%–20 %) to the modern European gene pool. In contrast, the Green et al.  study found a much more recent divergence time and made two striking observations that were highly suggestive of a substantial amount of admixture between Neanderthals and modern humans.
Jeffrey D. Wall and Sung K. Kim from University of California San Francisco write in PLoS Genetics what they found when they reanalyzed the data from the two original studies.
Wall and Kim’s reanalysis reveals inconsistencies between them and they believe that possible contamination with modern human DNA and/or a high rate of sequencing errors compromised the findings of one of the original Neanderthal DNA studies. The authors therefore recommend that we carefully evaluate published and future data before arriving at any firm conclusions about human evolution.
1. Noonan JP, Coop G, Kudaravalli S, Smith D, Krause J, et al. (2006) Sequencing and analysis of Neanderthal genomic DNA. Science 314: 1113-1118.
2. Green RE, Krause J, Ptak SE, Briggs AW, Ronan MT, et al. (2006) Analysis of one million base pairs of Neanderthal DNA. Nature 16: 330-336.
Article: Wall JD, Kim SK (2007) Inconsistencies in Neanderthal genomic DNA sequences, PLoS Genet 3(10): e175. doi:10.1371/journal.pgen.0030175