Better Humans

A new study published today in the journal PLOS Biology suggests that human beings are still evolving. Don't imagine, however, that it's the kind of evolution you see in X-Men — sorry, no mutant powers just yet. However, it's the type of evolution that could occur in one or two generations, and can prolong human life.

Researchers from Columbia University studied a large sample genome pool of 210,000 people from the United States and Britain. They found that certain genetic variants, particularly those found in people with Alzheimer's and those who are heavy smokers, as well as genetic mutations in those more prone to heart disease, high cholesterol, obesity, and asthma, appear less often in people who live longer. These are also the ones more likely to get passed down to successive generations, suggesting that the human genome is still weeding out what it deems to be unfavorable genetic strains.

Image credit: National Institutes of Health

"It's a subtle signal, but we find genetic evidence that natural selection is happening in modern human populations," study coauthor and evolutionary geneticist at Columbia and New York Genome Center Joseph Pickrell said in a press release. Pickrell and his colleagues studied 60,000 people of European ancestry and 150,000 people in Britain, genotyped by Kaiser Permanente in California and through the U.K Biobank, respectively.

Natural Selection in Action

When the expressions of certain genes are prevented, new traits that are more favorable evolve to offer a survival edge. These beneficial mutations get passed down to the survivors of each generation, as these mutations and their adaptive traits become more common in the general population.

In the new research, Columbia scientists found two so-called population-level mutations that stood out. One is the ApoE4 gene linked to Alzheimer's, which showed a drop in frequency in women over 70 years old. The other one that decreased in frequency is a mutation in the CHRNA3 gene, which is associated with men who are heavy smokers. The removal of both guarantee survival and longer lives, suggesting that natural selection has actively gotten rid of these mutations that usually act late in life.

"It may be that men who don't carry these harmful mutations can have more children, or that men and women who live longer can help with their grandchildren, improving their chance of survival," Columbia evolutionary biologist and study coauthor Molly Przeworski said in the press release.

To find other possible mutation combinations that affect human survival, most of which were difficult to spot, the researchers also examined 42 common traits — from height to body mass index (BMI). Predispositions for high cholesterol and LDL or "bad" cholesterol, high BMI, heart disease, as well as asthma, were linked to shorter life spans. Inversely, those predisposed to delayed puberty and child-bearing had lower death rates.

This study can help improve future longevity research, as it clearly shows that part of prolonging human life is found in the genes. Evolution takes care of it, so to speak. Of course, current advances in synthetic biology might be able to push this further. In any case, the human genome is doing its part.

"The environment is constantly changing," lead author Hakhamenesh Mostafavi said. "A trait associated with a longer lifespan in one population today may no longer be helpful several generations from now or even in other modern day populations."

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