Shortly after The Boy was born last spring, many people commented that he looked a lot like me (very few said he looked like his mom). Aside from making me feel good -- and slightly ticking off my wife -- it got me thinking: Do babies generally look more like their dads than their moms? And, if so, why?

On the face of it, it's not that hard to come up with an evolutionary explanation for why a baby would look more like their father. A baby can pretty much count on its mother taking care of it: a woman knows the kid it gave birth to is hers. Men, on the other hand, can never be entirely sure if they're a child's true parent. So a kid that's the spitting image of his/her dad would seem to have an evolutionary edge: it can convince the dad to stick around and take care of it.

And, indeed, there is some research to back this theory up. A 1995 study published in Nature (...) found that strangers asked to match pictures of one-year-olds to either the child's mom or dad had much better luck matching the child to the dad. Interestingly, when participants were asked to match 20-year-olds to either mom or dad, they were unable to. Strong proof, it would appear, that babies do in fact look more like their father than their mother -- and that this wears off over time.

But not so fast. A few years later, a research team in Belgium was unable to replicate the 1995 study, finding strangers were in fact no better able to match a photo of an infant with its father than with its mother. And, in fact, it found that the ability of strangers to match a child with either parent was lower than 50%.

And, when you think about it, this actually makes evolutionary sense, too. Because while looking a lot like your dad is an advantage for most kids, it could have been disastrous in our more barbaric past for a child who in fact was not related to their mother's partner.

Which brings us to the latest, and perhaps most convincing theory: Babies don't, in fact, look more like their dad. But everyone, especially the child's mother, has a vested interested in convincing the dad the kid is his spitting image.

This excellent blog post does a good job of summarizing some of the most recent research in this area. The author points out that fathers have a strong vested interest in ensuring a child is theirs. In fact, studies using MRIs have found men even look at their children differently than women: presumably searching for evidence of a familial match.

And the existing research makes a convincing case that, from an evolutionary perspective, a child's best bet is to look generic -- like he/she could be anyone's kid. But that the mother, and other family members, do their best to convince the father the kid looks like him. Quoting from the blog post:

Do babies really not look much like their dads? And do mothers really assert that they do? The answer to both of these questions is yes. A study of 160 couples with newborns tried to answer this by asking 60 couples together and 100 mothers alone which parent the baby resembled. When asked which parent their infant resembled, mothers with the father present replied 87.5% of the time that the baby looked like the father–but when the father was not in the room the paternal resemblance frequency suddenly dropped to 60.0%! Fathers reported self-resemblance only slightly more than half the time (51.4%). More than 1/3 of the time they gave no response since the mother apparently stepped in to answer first (the mother did not answer in only four cases). Unrelated judges matched the babies with their parents with success greater than chance, but were much more likely to match infants with their mothers, even when the father was the supposed best match.

I should point out that I'm not saying mothers are consciously conspiring to fool their husbands -- rather I think this behaviour is just a remnant from our evolutionary past. And there are plenty of great dads out there raising children that are not genetically their own (I myself have a great stepdad).

But these issues probably played out a lot different thousands of years ago -- when we were scrounging desperately for food on the savannah -- and it's interesting to ponder how that evolutionary path may have influenced how we view our kids today.

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