02/14/2013 03:30 pm ET

If Men Are Scarce, Women Have Smaller Babies

It’s about evolution; if dads aren’t around, mothers-to-be make subconscious calculations to balance their needs against those of their children.

In a report published in the American Journal of Human Biology, researchers say that in U.S. counties where women outnumber men, more babies are born underweight.

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