Science magazine reports:

Roughly one in five people are born with at least one copy of a gene variant called APOE4 that makes them more prone to heart disease and Alzheimer’s disease in old age. That the variant is so common poses an evolutionary mystery: If it decreases our fitness, why hasn’t APOE4 been purged from the human population over time?

Now, a study of nearly 800 women in a traditional society in the Amazon finds that those with the disease-promoting variant had slightly more children. Such a fertility benefit may have allowed the gene to persist during human evolution despite its harmful effects for older people today…

The Tsimané data also allowed the team to home in on how APOE4 may boost fertility: Women carrying it were slightly heavier that those without it, started bearing children about 1 year earlier, and had their next child a few months sooner. That fits with being more resistant to parasites, says siological anthropologist Benjamin Trumble . “Being in a better immune state means that you can then devote more calories towards growing faster, and then you’re able to reproduce faster.”

Thanks to Slashdot reader sciencehabit for sharing the article.

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