News from Gorilla Genetics
After the sequencing of the gorilla genome, the authors report unexpected results. The standard view of the evolutionary relationship between the African apes and humans is that chimpanzees and humans have a more recent common ancestor than either of them has with gorillas. A new genetic study that was now published in Nature found that it is more complicated. For 70% of the genes, the standard view is correct, but for the rest it is not. In 30% of the western lowland gorilla genome, the DNA sequences are more similar to the corresponding sequences from the human or chimpanzee genomes than the sequences of these two species are to each other. There are two possible explanations: either a mechanism called incomplete lineage sorting – when an evolutionary lineage splits, the gene variants may be sorted randomly and the resulting groups have different genes; the other possible mechanism is continued gene flow after the split of a lineage (occasionally individuals travel between the populations). Regarding the point of the splits of the human/chimpanzee/gorilla line and the human/chimpanzee line the authors give new estimates: 10 and 6 million years ago (so far, the estimates were 6 and 3.7 million years). The split between western and eastern gorillas is now estimated as 1.75 million years ago, although the split was not complete at that time and gene flow may have continued for about half a million years.
Summary of the article by A. Scally et al. in Nature 483, 169-175 (2012)