Scientists attempting to discover why some human genes evolved very rapidly believe that biased gene conversion (a non-adaptive evolutionary process) may be a significant factor, above and beyond Darwinian natural selection.
Describing their results in the journal PLoS Biology, the Uppsala University researchers describe how they identified fast evolving human genes by comparing our genome with those of other primates.
Surprisingly, the patterns of molecular evolution in many of the genes they found did not contain “signals” of natural selection. Rather, their evidence suggests that biased gene conversion (BGC) has massively speeded up the rate of evolution in certain genes. This process increases the rate at which certain mutations spread through a population – regardless of whether they are beneficial or harmful.
BGC is thought to be strongest in regions of high recombination, and can cause harmful mutations that can then spread through populations. Interestingly, the results lead to the provocative hypothesis that, rather than being the result of Darwinian selection for new adaptations, many of the genetic changes leading to human-specific characteristics may be the result of the fixation of harmful mutations. This contrasts the traditional Darwinistic view that they are the result of natural selection in favor of adaptive mutations.