EVER SINCE MY DAUGHTER was born four years ago, a popular activity in our household has been to sit around marveling at how much she resembles my husband. Which is fine. I have no problem with the fact that her eyes are his eyes and her eyebrows are his eyebrows and her chin dimple is his chin dimple. Even so, I have to admit that with my second pregnancy I occasionally indulged the thought that perhaps my turn had come, eyewise and chinwise. Yet ever since our son was born 18 months ago, a popular activity in our household has been to sit around marveling at how much he resembles . . . my husband.

"There's a reason for that," my uncle explained as we were sitting around one day, making the usual jokes about my being the putative mother, hahaha. He went on to explain that newborns are more likely to resemble their father. The reason -- researchers speculate -- is that the mother has just enjoyed nine months of intense physical bonding with her infant; the paternal attachment being more of an open question, the newborn resorts to shameless imitation as a way of winning over a potentially skeptical father. See, Dad! I really am yours! What a cheap trick, I said. Maybe so, my uncle replied. But it's also a good survival strategy.

Thus began my introduction to today's most fashionable child-rearing theory: Just as everything was once explicable as an Oedipal conflict, all childhood behavior is now seen as a survival strategy. That is, evolutionary psychology seems to have displaced Freudian theory as the hippest rationale for the way children behave -- evolutionary psychology being the idea that we do what we do (and even look the way we look) because it is in our genetic interests to do so. As a new parent, I have to say that I found the theory initially seductive. It did seem possible to believe that infantile cuteness (the big eyes, the little noses, the sweet sweet ears and fingers) is not a lucky happenstance or even a gift from God, but, rather, a carefully calculated means of attracting the requisite physical attention from father and mother both. Struck by how the infant's cry made me vibrate, instantly, like a tuning fork, I reasoned that this too must be part of a canny Darwinian plan. Over the years, though, I began to wonder: If crying is a survival strategy, what about whining?

What I mean is, I've now had occasion to ponder what seem to be evolutionary aberrations, puzzled by certain behavior patterns that can only be described as counterproductive. When I walk into the room, for example, and find that the 18-month-old has just seized a huge hunk of the 4-year-old's hair, what, exactly, is the survival strategy being played out here? Freud explained sibling rivalry as a contest for parental love; should I assume, now, that what I'm seeing is two closely related gene pools fighting for dominance? Is the younger child trying to ensure that in the unlikely circumstance that famine were to hit our household -- and all the Ovaltine, all the Cheerios, all the Trix yogurt, all the buttered noodle supplies were to be threatened -- he would get the lion's share? And if that's true, why do the two of them spend most of their time playing happily? What evolutionary purpose does sibling affection serve?

Or blanket-tossing? By that I mean the ability, which both kids developed independently, of dropping comfort objects out of the car seat while I am making my way through traffic. Not only dropping them but immediately howling for their retrieval, thereby requiring me -- the driver -- to reach back and grope awkwardly on the floor. In what sense is this a survival strategy for any of us? What about those occasions when my husband and I are about to go out, and my son clasps his arms around my legs? Standing there trying to disentangle myself, I explain to him that it's in his best interests if his parents are allowed, occasionally, to go out to a movie, thereby making it more likely that we will stay married and sustain a stable household that will push him toward a sound and healthy adulthood. Why does the gene pool not recognize this? Why, instead, does the child stand at the door hollering Mama?

What about climbing trees and subsequently falling out of them? Toddling into the road?

Turning on the hot water in the bath, then experimentally turning on the shower, to see if something interesting will result?

Aren't some behaviors, simply, mistakes?

In short, it seems to me that the evolutionary explanation is, like most theories, incomplete; that there seems something oddly religious about a scientific argument holding that everything, including a child's urge to pat strange dogs, has a higher purpose. Sometimes a tantrum is just a tantrum. On the other hand, I should point out that several months after their respective births -- a time when there was no danger, believe me, of the father not bonding with them -- both my children lost the dark hair that looked so much like his. When it came back in, it came back in lighter. More like -- well, more like mine. If that's not a good survival strategy, it's hard to know what is.

Liza Mundy's e-mail address is mundyl@washpost.com.