A few days ago, I met with friends and our conversation moved around, back and forth, and at one point touched upon genetics. It started with some thoughts about why my little daughter (and many other toddlers) refuse to eat vegetables. They are healthy and “good for you”, so why do children seem universally opposed to eat them? My answer: The environment where humankind evolved was full of green stuff, much of which was absolutely not “good for you”, and possibly deadly poisonous. In such a place, the genes most likely to make it into another generation that would survive long enough to be passed on yet again, would be those instructing the host to be better safe than sorry when it comes to new food (so here’s a perfect excise to all picky eaters that subscribe to the idea of evolution).
Now, given that my supermarket doesn’t sell poisonous broccoli (?), how come that we still don’t want vegetables when we are so young? One reason could be that evolution takes time, especially if there is no strong selection pressure on a given trait. It seems that most parents will work hard to make their offspring eat greens (there is a gene for that too, whose chance of propagating depends on the hosts insistence on making their descendants eat vegetables). In addition, the gene for picky eating might be coupled to a completely unrelated trait that is essential to survival (for an example of this, read about Dmitri Belyaev’s domesticated silver foxes, e.g. in Wikipedia).
Conversation moved on, and at one point, I wondered would happen if the was no selection pressure. Will our convenient life style make us slower, weaker and less intelligent; but more likely to eat vegetables? Perhaps, in the long term, if our genome is left entirely to its own.
Who knows, but I am sure the time isn’t yet. Instead, the selection pressure has changed. Instead of being our ability to withstand dessert sun, chew grains or outwit mammoths; basic fertility may be the new big thing. Fertility may never had been a thing to take for granted (and sadly surviving the birth of healthy children still isn’t in many parts the world), but our current environment isn’t helping: Male fertility is threatened by hormone disrupting chemicals in clothing, plant hormones in grain and who knows what else. And women accumulate environmental poisons in their bodies, especially breasts, from where it is passed on too missed children (read Florence Williams “Breasts: A Natural and Unnatural History” for further info). Also, we are having children layer and later, sometimes at an age that is past the life expectancy in the more primitive societies of humankind’s past. So maybe that is where evolution is taking us now: less vulnerability to the chemicals that are all around us and a later menopause.
(lots of) Time will tell…