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We are still evolving – very slowly. In the 20th century, people in the UK evolved to be less likely to smoke heavily, but the effect was tiny. So claims a study of 200,000 genomes.
A population can be described as evolving when the frequency of gene variants changes over time. Because most people in rich countries now live well beyond reproductive age, some argue that we have stopped evolving because natural selection has been weakened. But several recent studies claim we are still evolving, albeit slowly.
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Now Joseph Pickrell at Columbia University in New York and his team have analysed human genome sequences to spot gene variants that are becoming rarer. One variant, of a gene called CHRNA3, is associated with heavier smoking in those that smoke, raising their risk of a smoking-related death.
Slight decline
Comparing people over the age of 80 with people over the age of 60, Pickrell estimates that the variant has declined by 1 per cent between generations. However, his team was not able to prove this, as they did not have any genomic data from people under the age of 40.
A variant of the ApoE4 gene that is known to increase the risk of late-onset Alzheimer’s disease, as well as cardiovascular disease, may also be getting rarer.
These variants might be becoming rarer because many people now have children in their 40s and 50s, when people with such variants are at greater risk of dying. 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 doesn’t necessarily go in the same direction for long. If smoking dies out, for instance, selection against variants linked to smoking-related deaths will stop.
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Journal reference: PLoS Biology, DOI: 10.1371/journal.pbio.2002458
Read more: Are humans still evolving? Growing evidence suggests we are
This article appears in print under the headline “Our genomes reveal modern-day evolution”
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