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The View from Above

Babies on the Beach

It occurs to me on rereading my post from the other day that about 3/4 of what I was thinking about infants and evolution and the beach stayed in my head and didn't make it to the page. Here's a bit more:

I've been watching all these Discovery Channel/BBC nature programs -- Walking With Cavemen, Walking With Prehistoric Beasts, etc. -- which all have a very strong evolutionary themes: lots of action focused on predators and prey, hunting, breeding behaviors, etc. Relatively little attention in these stories is given to how infants and juveniles survive long enough to have the opportunity to do these things. As nearly as one could tell from these series, young creatures survive by hiding and sticking close to their mothers, and occasionally by watching their mothers do something and imitating.

Being in charge of the well-being of an infant nearly 24 hours a day, I observe a lot of behaviors that don't fall into these limited categories. The one most relevant to our beach experience is how infants constantly put things in their mouths: shoes, rocks, paper clips, dust bunnies, twigs, cat hairballs, grass, leaves, and paper. From baby books, I'm given to understand that this is an oral exploratory stage and is (presumably) neurologically necessary. As parents, we are strictly instructed to keep anything out of the baby's mouth that might be a choking hazard or might have germs on it. This is because babies can very easily die by choking and also because one wants to keep them from getting diseases. The mouthing behavior comes with a very high evolutionary price tag. Even in our pampered, mostly post-evolutionary environment, it still carries a heavy cost and consumes a lot of my time and attention every day. What are we to make of this?

I do not buy the idea that this is simply a neurological side-effect of other aspects of human development. The baby is very clearly foraging in addition to exploring and teething.

I've been a lot less orthodox about keeping stuff out of Elizabeth's mouth than I was in this struggle with Peter. When we're in the grass, I let her pick grass and leaves and put them in her mouth and then I tell her don't eat that, because as her mother I am supposed to be teaching her what to eat and what not to and -- it seems to me -- she'll learn faster this way than if the grass never makes it to her mouth in the first place. Over the past two months, she has developed at least five distinct modes of mouthing: sucking (rocks on the beach which taste salty), exploring (a paper clip, a dried leaf), teething (putting something in her mouth for the purpose of exerting counterpressure in the area where she has teeth coming in), tasting (establishing whether prospective food is actually good to eat), and eating. Over time, the distinctions between these behaviors has become clearer (which I think decreases her chances of choking by a lot), and things she seems to be tasting or actually trying to eat are much more likely to be actually edible or close to edible -- dandelion leaves, a fallen crab apple, a clover blossom, and, of course, seaweed.

A baby let to go her own way on a suburban lawn will find some nutrition, but not much. By comparison, a baby on a sheltered beach with tide pools and tide flats rich with life will find a whole lot more nutrition: not only highly nutritious sea vegetables, but also snails and small crustaceans. (When Peter was just under 2, I took him to the beach. I caught a tiny crab and gave it to him to hold in his hand. Peter popped it right in his mouth and ate it.) Because of water pollution, overfishing, and other factors, our beaches today are much less rich in life than beaches were several hundred years ago. What might Elizabeth have found to eat on the beach in Maine in 1600?

At some point, babies mouthing behavior would have to have been strongly selected for for it to be this strong and indefatigable. Here is my thought -- the mouthing behavior of babies would have substantial evolutionary value in a tidal beach environment, perhaps more than enough to overcome it's evolutionary cost.

In general, I think, evolutionary pressure on the young is much stronger than evolutionary pressure on adults because it is a bottleneck: you cannot reproduce unless you reach maturity. Certainly, adults exert a lot of effort to keep their progeny from dying. But young creatures do a whole lot more than hiding, clinging to their mothers, and imitating. And what is missing from this picture may be more important than what adults do.


Mouthing books is really an important early literacy skill.

This literary skill is strongly discouraged in our household. Handling books, yes. Mouthing them, no.