I belong to this kind of biologists that takes natural selection quite seriously, though this is a conceptual bias I rather easily acknowledge. It doesn’t mean that I’m completely indifferent to other processes impacting biological evolution neither*. I’m perfectly aware that the omnipotence of selection to shape life is a long standing and recurring debate, and many aspects of life indeed clearly don’t fit the simplistic view of adaptive wonderland (a classic strawman by the way). That said, I don’t think blowing up everyone as soon as natural selection is invoked as a so interesting position. Sure, it is important to remind lay people that many other things impedes selection to achieve its powerful canalisation -drift, constraints (be they devo or of any other kind) and so… But please let’s be careful not to throw the baby out with the bathwater: there are still so many features which are best explained by natural selection (and for which the closest ‘best’ explanation would be intelligent design rather than things like randomly drifting developmental pathways).
So after digressing introductionarily, this is just an exercise in just-so-story (one more I know), that is, speculating about natural selection on a very curious fact, for the post today… A fact about babies. Well, pre-todds rather. If you read Seeds Aside since some time, you know why it doesn’t deliver daily substance (the carny deliver gets to somebody else, but somebody special).
There’s something about babies’ diet that I noticed in my belittles, and in other babies (and got confirmed by doctors as well). Grossly, something happens around one, and last a few months (hum, up to a year?), not that long after they are introduced to a more diverse food: they begin to refuse vegs even after weeks of acceptance. Mine is going as far as regurgitating anything that’s above a rather low level of fibers content. On the other hand, anything sweet like potatoes, carots or sugar beet is accepted.
Lately, I wondered if this actually is not simply the result of natural selection (go, go shoot me! I told the S word…). Fibers rich food has certainly a digestive cost, and indeed, it is recommanded as a way to lose weight without efforts (because you may spend more energy trying to digest it than what you get paid back in the process).
So it’s not that unthinkable if the price to pay for ingesting too much fiber as a baby is enough that regurgitating would be selected for. Especially if food supply was short of some sort, which is not the most unlikely historical hypothesis (compared to today). “Get the most rewarding food, don’t indulge in fake rewards“… Moreover, since parents are selected for taking good care (or at least -unfortunately- one of them), rejecting the food may also translate into more care (and more good carny/sweety food).
That’s just a speculation, I’m not aware of any published data that would confirm this view. But it’s interesting, and has some potential. Of course it is in need for confirmation, but hey, I’m a plant biologist. I was just trying to get my son have a minimal vegs in, not finding my next research project…
* Indeed, I also had the opportunity to demonstrate clearly and properly (and not just evoking passing by) the very existence of developmental constraints (no! just that!!). Not something you would expect from a basic stereotypical ultra-darwinist, would you huh?