We’re still evolving – very slowly. In the 20th century, people in the UK were less likely to smoke heavily, but the effect was small. So claims a study of 200,000 genomes.
A population can be described as evolving when the frequency of gene variants changes over time. Since most people in rich countries are now well past reproductive age, some argue that we have stopped moving because natural selection has been weakened. However, several recent studies claim that we are still evolving, albeit slowly.
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Now Joseph Pickrell of Columbia University in New York and his team have analyzed human genome sequences to identify gene variants that are becoming increasingly rare. A variant of a gene is called CHRNA3has been linked to heavier smoking among smokers, increasing the risk of smoke-related death.
Pickrell compares people over 80 to people over 60 and estimates that the variation has decreased by 1 percent between generations. However, his team couldn’t prove this because they didn’t have genomic data on anyone under the age of 40.
A variant of the ApoE4 Genes that are known to increase the risk of late-onset Alzheimer’s disease and cardiovascular disease may also become rarer.
These variants could become rarer as many people now have children in their forties and fifties, when people with such variants are at higher risk of death. Even a subtle impact on lifespan can have a relatively strong evolutionary effect over many generations, says Pickrell.
But the trend might not last. Animal studies have shown that evolution does not necessarily go in the same direction for long. For example, if smoking stops, choices will be turned against variants related to smoke-related deaths.
Journal reference: PLoS biology, DOI: 10.1371 / journal.pbio.2002458
Continue reading: Are people still developing? Growing evidence suggests it is us
This article appears in print under the heading “Our Genomes Reveal Modern Evolution”.
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