Fat enough for you?
Barry Popkin: Nutrition Action Healthletter, June 2006
I'm a great fan of evolutionary psychology, which (to oversimplify) says that most of our psychological traits were genetically advantageous (promoting survival to reproductive age followed by reproduction itself) way, way back when. Or to over-oversimplify, we're atomic-age bodies with stone-age brains.
So, for instance, dividing the world up into "us" and "them" (we're the good guys, they're suspect) might have made total sense when our ancestors lived in tribes and vied with neighboring tribes for limited resources. Cooperation with the rest of "us" and aggression towards "them" helped our genes on their long journey from then to now. Today we call it (destructive) nationalism; back then it was (constructive) tribalism.
Or, on another tack, it's long been suspected that our passion for sugar, starch and fat (think double-thick chocolate milkshake) is inherent--we crave that stuff because it wasn't so plentiful a million years ago, and what little our great-great...grand-mothers and -fathers got of it was good for survival, good for reproduction.
Another (mostly overlooked) way our genetic legacy leads to poor health is the way humans evolved to respond to liquid and solid intake, that is, separately. Until very recently, human liquid intake consisted soley of water (and breast milk as infants). If drinking a lot of water had alleviated hunger, our ancestors would have starved to death. So our brains evolved two separate systems, to ensure we both drink enough and eat enough. How much we drink doesn't affect how much we eat, because all our calories used to come from food.
So nowadays, when we chug, say, a couple of cokes, it has no effect on our hunger. Our brains are still on automatic, "telling us" to eat whatever we would have anyway, if we hadn't drunk the cokes. So now we end up toting an extra 300 calories that convert into extra pounds.
In 1977-78, Americans (age 2+) got about 3% of daily calories from soft drinks.
In 1999-2000, we got about 7%.
100 years ago, that percentage was zero. Go figure!