Maternal competency and natural selection?

So, as a woman, am I wired to be a mother? Is there something on my X-chromosomes, or in my lack of a Y-chromosome, or in my female hormones that programs me to know how to care for an extremely helpless newborn baby? In those early days, I wanted that to be true, but I wished I felt more certain about it all.

When I seek evolution as a comfort in all this, my thoughts fall into a habit of thinking through natural selection. I try to check off the boxes, which are basically, that the trait is 1) variable in a population, 2) affects the evolutionary fitness of the individual (how many offspring survive and, in turn, reproduce), and 3) is heritable. If all these things are true, then 4) the trait should increase in the population if it is good or decrease in the population if it’s bad.

As far as maternal behavior being variable in a population, I think that is self evident. Isn’t it? Isn’t that why there are so many different books on the subject, so many philosophies, so much judging about it? In a paper called “Evolutionary roots of intuitive parenting: maternal competence in chimpanzees” (Bard, 1994) the author evaluates maternal competence in chimps. It’s done in captivity at the Yerkes Primate center, though if we’re interested in hard-wired, genetic behavior that shouldn’t matter. Key points were that mothers spent a lot of visible time cradling their infants (~70%). Competent mothers cradles and gazed at their infants more, and stimulated them, encouraging them to develop their motor skills. “Marginal” mothers showed a real difference in these skills, failing to respond as much to infant crying and not keeping them as close by.

Infants of the marginal mothers didn’t fare as well, some were injured. This brings us to #2, does maternal behavior affect evolutionary fitness of the individual? Does it matter if a mother is competent or marginal? This is a longer term question, and I don’t feel like I have sufficient research or knowledge to answer this one yet. On the one hand, there are plenty of studies out there to prove infants need a mother not just for nutrition, but for nurturing also. Here’s a brief look at the saddest set of experiments ever, by Harry Harlow:

I haven’t gone back to the source papers on these, but what I learned in Psych 101 in college was that monkeys reared without mothers are not properly socialized, which I assume affects their ability to find mates and mother offspring of their own. It’s hard to apply this to a more naturalized setting, but it seems fair to assume better mothers have better adjusted offspring. Does that translate to increased reproductive success? Because we should only expect to see behaviors selected for if they increase reproductive success. I could imagine a contrary scenario; what if cold, marginal mothers ignored their offspring and just continued to have lots of them? Maybe it doesn’t matter if the mother is marginal, in which case you shouldn’t see any selection on competent mothering.

But what you see in monkeys, apes, humans, is extremely helpless infants, that are carried by their mothers and form an important and long-lasting relationship, perhaps the most important, long-lasting relationship (depending on species). Competent mothering seems like a set of traits that must be selected for, since helpless infants (with their large, slowly developing brains) have clearly been selected for.

Then there’s that whole heritability part. Is “mothering” as a set of traits coded for by genes that we can locate? Is there evidence for this? Are there mothering genes, and do the forms you get predict whether you are a competent or marginal mother?

Because the alternate hypothesis would be that mothering is largely learned, culturally transmitted as we learn from our own mothers and mothers around us.

Next time: cultural transmission of mothering practices.


On taking home a newborn

Bringing home a newborn was very scary for me. I don’t think I’d actually ever held a newborn before I held my own. Some people may have much younger siblings, or cousins, or close friends to share babies with, but I had never had that experience. So when we headed home with our first baby, I felt completely unqualified, and my husband felt at least as much so.

[This is picture from Huffington Post. I tried an image search of “newborn baby” and all the pictures looked super fakey-fakey, the babies were all scrubbed and at least one month old. None of them looked like a baby that had actually just been squeezed through a birth canal and had a conehead. I searched “red newborn baby” to find this one. Even this one is not totally fresh from the womb.]

Maybe some mothers feel more prepared; maybe they’ve read more books than I had 🙂 or had experience with babies, but generally I know this fear is a common experience. The inability to sleep, the listening every five minutes to see if they’ve stopped breathing. I think, for most women, it’s the biggest responsibility by far that we’ve ever had. It was terrifying to think: this little human is dependent on me to eat, to be clean, to hold its head up for god’s sake. My husband felt the weight of this also, of course, but he soon returned to work. Those were long days, just me and the baby, whose needs were both so simple and so demanding.

I have three children now, and while taking home babies #2 and #3 was a little less unnerving, those first nights were still worry-prone and spooky. And I still would never call myself an “expert” on newborns. I got through it, my children survived, but there was always a great deal of mystery in it. My brothers gave birth this year year, and when I saw their wives, looking exhausted and holding a tiny red baby, I give a little shudder and thought, glad that’s not me. Because while having a newborn is incredibly special, and there is nothing at all like it, it is so, so hard. With each baby there were always moments when I looked into their expressive yet mysterious dark eyes and wonder, what are you thinking? What do you want? And I felt like I should have known more, should have been more of an expert.

Certain biological things just happened, with respect to motherhood. The whole process of labor, especially the first time, seemed like a possession, something happening to me, not from within me. The contractions, both before and after delivery, happened whether I was ready or not. The milk came in, making me swell up and spurting out at unpredictable times, without any action on my part. So I felt it was only fair to assume that, like these physiological signs of motherhood that had to be part of my genetic programming as a woman, I had to have some mothering instincts programmed in too, right?

Maybe. The other possibility, which didn’t really occur to me later, is that motherhood practices are culturally transmitted. That I learned them, from my own mother, from other mothers in my life, and it was those that I could use as a guide. That was a hard one for me, because if this was the case, why did I feel so clueless? My sister and mother were my greatest sources of advice, but we were separated by plane flights and time zones. Maybe society has changed in a way that our learning of these mothering practices has been interrupted, or there isn’t as much modeling around us as there once was.

As with any question of nature and nurture, the answer is always that some of both of these are at play, and the real question is how, and how much of each, are at play.

On parenting books

I never really read parenting books. I’m neither proud nor ashamed of this. I did read Happiest Baby on the Block; I thought that was pretty good, pretty reasonable, it fit with my ideas of what you should do with a newborn. Comfort them when they cry, swaddle ‘em up. Hardly revolutionary, really, and you could probably get the gist pretty well from the introduction. I’m not knocking it; we used the swaddle, the Shh, the swinging, and whatever the fourth S was, and it actually is the only parenting book I actually finished and implemented ideas from.

[Thanks Dr. Karp!]

From there I got into some more hard-core sleep books. One, actually. I remember being a little scared about the introduction, which laid out a complicated, multi-step outline for sleep training, the details of which would be fleshed out in some two-hundred pages to follow.

I read a few chapters, but was gradually turned off. First, the idea of sleep “training” a baby was weird to me, and I didn’t like having to follow a really strict schedule of feeding and napping. I myself am not that scheduled, so it seemed strange to expect a newborn who had recently been enveloped in a warm, watery world of total darkness, to be. In addition, there was a lot in the book that made me feel bad. I wasn’t supposed to nurse the baby to sleep. Shit, I totally did that. I was supposed to put the baby down for a nap in her crib only with the same routine at the same time every day. Crap, not doing that either. And so on.

My justification (or rationalization) in returning to long periods of nursing the baby to sleep while reading novels was…should it be so hard to figure this out? I don’t think my mom read sleep training books, and my siblings and I all seemed to sleep fine. And not just my mother, but what about my mother’s mother, and my great grandmother, and back and back and back? And the biologist in me started thinking about the long chain of mothers, who have passed along not just maternal parenting genes but maternal practices, and I want to know more about that. Like, isn’t there some genetic and cultural inheritance that I can rely upon to keep this newborn fed, rested, alive? If there is one thing that you, me, and pretty much every other adult walking around on planet earth have in common is that someone, most likely our mother, succeeded in raising us from a red helpless floppy infant into someone who could survive.

I’m pretty sure proto-mom back in her cave, however long ago, was not reading parenting books. And that’s not to say mothers today could improve their practice by reading parenting books; I probably could be improved by reading a few good ones. Maybe it’s more of a rationalization for my not wanting to read parenting books, to try to rely on evolutionary history, to say, chimps and gorillas don’t read books, my great great grandma(s) were unlikely to read books, shouldn’t I come equipped with the know-how to figure this out?

But the reality is, it felt so damn hard. Feels so damn hard. How can something so fundamental, so essential to being human, feel so hard? No one checked to see if I was qualified when they let me take my newborn home. More on that to come.

Parenting like a primate

So…parenting like a primate. I am a parent. I am also a primate, as are you. A primate I mean, not necessarily a parent. Although I can be fairly certain in assuming that you have parents. You have, or had, a mother who birthed you, and probably raised you, with various degrees of help. You have a father who contributed 50% of your genetic share, and perhaps much of your parental care as well.

This may not sound special to you. You share it with every other human on the planet, and with other primates, and mammals in general. But it actually is kind of special when you look at life as a whole. And if you think about you, compared with every other creature that lives or has lived on earth, you can get to asking (and I certainly do) how much do we share with other primates, with other mammals, with birds, insects, fungi, bacteria? We’re used to thinking of humans as the dominant life form on earth, but that’s a fairly narrow view. Two of the three domains of life (Archea and Bacteria) are single-cellular, and reproduce through cloning, totally bypassing the idea of mother-and-father. And lots of animals (think insects) have parents, but not parents who hang around to offer a lot of support and nurturing.

I am not an expert in parenting. I have three children, and make it up as I go. I am not a scientific expert, although my degree is in biology. Most of my career has been as a high school  biology teacher, and so if I am “expert” in anything it is in understanding broad themes in biology and making them applicable to everyday life, to the things normal people care about. The purpose of this blog is to try to understand parenting, and mothering more specifically, from a biological perspective, mainly through the lens of evolution. How much do we have mothering “instincts,” and how much of our mothering skills are learned, transmitted from our own mothers, or mothers around us? Are you and me baby ain’t nothin’ but mammals (sorry), or are humans in their own distinct categories as parents? I’m relying on personal anecdotes, and using research where possible and applicable, and inevitably asking many more questions than I’m answering.


Picture from