Drunken monkeys

A recent New York Times article discussed alcohol consumption in animals. An amusing and important topic for all of us, I would highly suggest reading the comments to find out more about this delightful subject. Did you know that some pigs have been known to make alcohol by leaving some of their feed untouched, allowing it to ferment? Those clever bastards.

This leads me to something I’ve been meaning to talk about for a while: the drunken monkey hypothesis. Let’s say that you were a scientist who wanted to study why animals consumed alcohol. How would you go about this? Apparently, you would literally wander through a jungle, picking fruit up off the ground and throwing rocks at trees in order to knock it down. Then you would compare the amount of alcohol (ethanol) in the fruit.

What this group found was that the pulp of slightly overripe fruit, such as that drunkenmonkeyfound fallen from branches, had a high level of ethanol (an average of 4.5%). They suggest that this helps ward off bacterial invasion, allowing the fruit to stay fit for consumption longer and thus promoting seed dispersal by foragers. They also think that consumption of ethanol has an appetitive effect, so the animal would feel hungrier. Evidence from fruit-eating animals show that they can clear the alcohol from their systems much faster (with much more active alcohol dehydrogenase) than their non-fruit-eating brethren.

I guess the evolutionary idea is that we now associate alcohol consumption with nutritional reward. Alcoholism would then be akin to obesity: a problem of nutritional overconsumption. I’m not sure how much I agree with it; it would seem that the side-effects of alcohol would be a stronger determinant of enjoyment than the taste. But then, maybe that was the coevolutionary strategy? ie, you get drunk but you have to eat healthy first! Probably not, but entertaining nonetheless.