Sunday, August 29, 2010

Survivors and Foragers: speculation on group selection and obesity

Speculation is cheap.

What if one of the variables in human weight control was activity response to caloric restriction?

Ok, so that's not too speculative. We know obese humans decrease activity when they diet. This is one reason that, in a nation of very cheap calories, so many Americans are obese. When these people diet, they are put into an involuntary lethargic state.

It's a behavior that makes lots of evolutionary sense. Throughout most of human history these people would have been survivors of famine. We can call them The Survivors.

But what if there's a distribution across the population? What if there are people who respond to caloric restriction with increased activity? That makes a sort of Darwinian sense too, particularly if you think of humans as group selected Big Brain Bees (BBBs). Think of these people as Foragers, they roam from the Hive looking for new options. In todays world, some of them are anorexics, but mostly they're just slender.

I am positive that if I knew the scientific literature on obesity, and I knew the right search terms, I would find articles exploring this model. It feels plausible that there's a range of responses to calorie restriction -- from Survivors to Foragers and everything in between.

Of course feelings are the fount of grant proposals, not of science. This is, however, a testable hypothesis. So it could turn into science.

There are implications for drug discovery. If this model were correct, the magic obesity pill would convert Survivors into Foragers. So pharmas should be looking for Foragers to study ...


Anonymous said...

I'm half-convinced that seasonal affective depressive disorder--maybe depression in general--is an evolutionary response by farming cultures that have winter.

If you're in Northern Europe or Asia, and you're part of a farming culture, it makes sense to stay in bed 20 hours a day when it's dark! There's not much work to do on the farm during the winter, and when you are lethargic and sleep, you use many fewer calories. Especially when it's 10 degrees outside and you have to keep your body at 98 degrees. Smartest thing to do to survive winter is huddle under a blanket and just eat the bare minimum to survive.

Seasonal depression is a VERY good way to get you to do this. For all we know, bears are terribly, terribly depressed when they hibernate.

I'm honestly half-convinced that depression is just a survival mechanism run amok, poorly adjusted to a world where we no longer starve to death in the winter.

Anonymous said...

Interesting theory. Another related data point is that Icelanders seem to have acquired a total genetic immunity to S.A.D. in the past 900 years, but they had to husband animals through the terrible, dark, winters there.