Humans
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Distinct human populations living on separate continents have followed largely similar patterns of evolution since the onset of the Neolithic period, according to a new study. This suggests that, despite occupying different climatic zones, we’ve all been influenced by the same selection pressures – many of which appear linked to the adoption of agriculture.
The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.To understand how our genes have changed over the past 10,000 years, researchers examined DNA from 7,244 people from both ancient and modern populations in Europe, East Asia, South Asia, Africa, and the Americas. Their findings – which have yet to be peer reviewed – suggest that our genomes have undergone selection at 31 different locations, many of which are shared by people from all over the world.
According to the study authors, this finding is suggestive of “extensive parallel or shared adaptation.” In other words, we’ve all evolved to meet the same challenges, regardless of the environmental, social, or cultural backgrounds in which our ancestors developed.
Notably, the researchers point out that the strongest signals of selection “are all plausibly related to the consumption of agricultural products.” For instance, in the last 100 generations, there appears to have been intense pressure on the genetic variant underlying lactase persistence, which enabled people to drink milk beyond infancy.
This pattern was particularly noticeable among European populations, but other trends were shared globally. Among the most significant of these is a change in the FADS1 gene, which enhances our ability to metabolize plants, and may have proved hugely beneficial following the advent of farming.
Another concerns the gene ADH1B, which impacts the way we metabolize alcohol. Previous research has highlighted a variation of this gene among East Asians that limits their tolerance to booze, and the authors of the new study found evidence of a similar evolutionary trend in Europeans.
This suggests that we may be more lightweight – at least when it comes to drinking – than our Neolithic ancestors were, although the specific variant that causes East Asian boozers to turn red in the face was not found in European genomes. As such, the authors say it’s unclear if selection for this particular reaction to alcohol is shared worldwide.
Yet another key trait that shows signs of strong selection is the waist-to-hip ratio (WHR) in females. Given that an increase in WHR has been linked to enhanced fertility, one might expect humans to have evolved in this direction, yet the study authors found that this trait is actually under stabilizing selection – meaning our genes have adapted to keep WHR within tightly fixed parameters.
The researchers aren’t sure why this is the case, but suspect that limiting WHR must bring some beneficial trade-off. Moreover, the fact that this stabilizing pressure was noted across all continents suggests that whatever reason nature has for keeping waists in check, it’s probably a good one.
A preprint of the study is available on bioRxiv.
