An intriguing new piece of research by US and European researchers describes how human evolution may be disconnected from our traditional view of Darwinian natural selection.
Life on Earth is subject to evolution due to mutation and natural selection. The latter process describes how individuals with more favourable adaptation to their environment will contribute more to the subsequent generation’s gene pool than those with less favourable traits, hence it is often referred to as “survival of the fittest”. This ‘fitness’ is manifest in nature where elaborate rituals to demonstrate strength and prowess are commonplace. In humans too, we have traditionally viewed our evolution as following a similar path – where we adapted to become bipedal and develop complex societies, essentially driven by ‘fitter’ individuals enjoying greater reproductive success.
The new study, however, suggests that rather than human evolution being driven by natural selection, it has long been the case that humans themselves shape evolution. A study of human male genetics via the Y chromosome (most studies to date have focused on female inheritance via mitochondrial genes) revealed an acute bottleneck in male genetic diversity some 4,000 – 8,000 years ago. This was at a time when female genetic diversity was increasing, and so what was the cause? The research suggests that the timing is crucial – since this period corresponds to the transition from Neolithic hunter-gatherer societies to agrarian societies, a consequence of which was the focus of wealth and power to relatively few individuals and an increase in the reproductive success of these few ‘socially fit’ males.
Given that wealth accumulation is such a strong societal driver today, it is plausible that this is still a strong driver of human evolution – time will tell!
The original research article appears in the journal Genome Research: http://genome.cshlp.org/content/early/2015/03/13/gr.186684.114