Happy families: heartwarming domestic scene or symphony of self interest?
Evolution may make men ignorant and gullible.
Gentlemen: ignorance is bliss and gullibility is the best policy. A new mathematical analysis suggests that evolution favours babies who don’t much resemble their fathers, and males who believe their partner when she says a child looks just like him.
Anonymous-looking newborns make for uncertain fathers. But they also allow men to father children through undetected adultery, Paola Bressan of the University of Padova calculates1. The assertion - common across many cultures - that babies are the spit of their dad, is a way to get men to care for their offspring despite their uncertainty, she adds.
So everybody’s happy? Not quite: if all babies are anonymous and fathers are uncertain, males would invest less in kids whether they sired them or not.
A mother’s strategy to counteract this, says Bressan, could be to remark on the baby’s likeness to his father. Her mathematical model shows it can benefit a father to believe these assertions and increase his care for the child, as long as the chance that he is being deceived is slim enough.
Denson McLain, a behavioural ecologist at Georgia Southern University likes this idea. "The harm to a father of being sceptical towards is own children is greater than the cost of rearing someone else’s child," he says.
McLain has found that mothers remark more on their baby’s resemblance to their partner if he or his relatives are there to hear her than if he is absent.
Pagel, however, doubts that evolution would favour trusting males. The warm glow that dads get from hearing that junior has their nose might simply be "good old-fashioned vanity", he suggests.
JOHN WHITFIELD | © Nature News Service
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