Mennesker fra ulike kontinenter har utviklet genetiske forskjeller de siste 5.000 år. Og forskjellene økte de siste 1.000-2.000 år, viser studier. Men i moderne tid har trenden snudd: genblandingen er så stor at forskjellene minsker.
Races have evolved away from each other over the past 10,000 years, according to new research that challenges standard ideas about the biological significance of ethnicity.
A genetic analysis of human evolution has shown that rather than slowing to a standstill it has speeded up, with different pressures on different populations pushing racial groups further apart. Scientists behind the findings suggest that European, African and Asian populations grew genetically more distinct from each other over several thousand years, as their environments took them down different evolutionary paths.
This would call into question the popular scientific view that race has little or no biological meaning, as the genetic similarities between ethnic groups greatly outweigh differences.
While this remains true – all humans share more than 99 per cent of their DNA – the new work indicates that variations tend to differ between races, and that these became more, not less, pronounced.
The research identified evolutionary currents only in past times. In the modern era, greater movement and gene flow between the continents has probably slowed or even reversed patterns of increasing genetic difference, making the evolution of separate human species virtually impossible.
Armand Leroi, Reader in Evolutionary Biology at Imperial College, London, said: «In principle, this could have led to speciation if it had continued. In practice, it has got to be the case that that cannot happen now. The reason is that this study has looked at largely separated populations in the past, but everything about human history since the Industrial Revolution weighs overwhelmingly against separation and thus against speciation too. Huge increases in gene flow are going to wipe this trend out.»