Adults drinking milk

The other day, a friend announced (with a little more emphasis than necessary, but we are used to that from him) that adults drinking milk was "an aberration". We didn't really get into the details of why he believed this - the conversation went off on another tangent - but I imagine it is because milk was "designed" as food for infants, not adults. So in a sense, he was arguing that people should act their age. 

I responded by mentioning a theory that certain adults (and most notably the ones in northern Europe and North America, with less sunshine) drink milk because they need it as a vitamin D supplement. And that this was another case of natural selection, namely in the sense that migration to sun-impoverished areas is only a choice for people who are able to digest milk as an adult. (And, I would add now, that this in turn is a result of population pressure). 

But I do agree that it doesn't feel natural, if only because I know of no other species where the adults drink milk. (I have heard that certain snakes will drink goat's milk, but that does not count: that would be more like humans eating fruit, which is basically food for the infant plant/seed).  In fact, you could argue that we should have never left the subtropics, not only because of the lack of sun as a source of vitamin D, but also because of the temperature, which has forced us into wear clothes. 

Of course, I realize we do not really have a choice (there is no going back), and I also know that moving out of our climatic comfort zone has given rise to a lot of interesting developments, but - and now comes the twist - accepting the premise that we do not belong here immediately and completely validates a fallacy that I get more emphatic about than strictly necessary, namely the idea that we should only eat what grows in the area. Most diets nowadays seem a bit simplistic, but that one really takes the cake. We were not designed to live only on apples and lettuce, and there is not reason to restrict ourselves to them. 

It is currently 7 30 in the morning. Time for breakfast. I think I will have a bowl of cereal. With milk!