There's lots of things in human psychology for which an adaptationist explanation makes some sense. We desire food and sex because creatures that desired these things were more likely to live and reproduce back in the old times, and we carry these traits as the descendents of those creatures. The capacity for laughter and the appreciation of music, however, seem more difficult for adaptationists to explain. Would a creature that laughed or that enjoyed music really produce more viable offspring than a creature that didn't? Maybe there are some minor ways in which these things are adaptive (stress relief?) but it's hard for me to make a serious case for them. I can see how they might be adaptive if a large percentage of the population (and particularly your potential mates) already has a sense of humor or likes music. But I'm wondering how this stuff gets going in the first place so that a large percentage of the population has the traits in question.
My guess is that if you throw together a bunch of complicated, evolved modules in the brain -- language processing, emotions, auditory processing -- you get weird emergent capacities on top of those things that weren't specifically selected for. If there aren't any selection pressures on the emergent abilities, they just stick around. If I remember correctly, Gould talks about this kind of thing in "The Spandrels of San Marco."
Personally, I'm not as enamored of adaptationist explanations as some people are. Developmental factors, random genetic drift, and most importantly the number and severity of the mutation steps between a previous stage and a subsequent one are a huge part of the explanation. Sure, natural selection plays a role, but there's no reason to think it'll be the central factor in explaining why we are the way we are.
Sunday, January 09, 2005
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Laughing is connected to social relations, cooperation, dominance, etc. These affect who gets fed, who gets chosen for breeding, who doesn't get eaten.
Singing ability in birds and whales is about mating calls and territory marking. In humans it may be related to language using. Think of rock stars and groupies - good singers have higher social status than nonsingers. Voice is a cue for pair bonding. Isn't it that way among werewolves?
I can see how all those social and status things get going once a lot of people are already into music and laughter. But if you're the first guy who has a sense of humor or who appreciates music, you don't get any of the advantages connected to making people laugh or singing to others. So how do you account for the first laughers?
If you need to make the argument "once a lot of people are already into music" for music in humans, doesn't the same principle hold for birdsong?
For a Cognitive Science class I was TAing last semester, I read an article by Geoffrey Miller in which he argues (like gt does, above) that humor and music developed by sexual selection. One of the mechanisms he suggested was as fitness indicators by handicap: that is, if an individual has the time to sit around singing (even more so, the time and resources to create art) and still manages to, like, feed himself and remain healthy, that indicates that he's an exceptionally skilled hunter/gatherer: in effect, he's able to hunt/gather as much as he needs to support himself, and still have time left over to waste on singing and painting. (And then once he has offspring, if he lays off the art a bit he'll be able to support them, too.) So—initially—if you're attracted to individuals who create art, your offspring will likely be more successful; and then once that gets off the ground, even once art and music lose their correlation to survival ability it could sustain itself through sexual selection.
Miller's analysis of the original get-off-the-ground fitness-indicator value of a sense of humor was more confusing, I thought, but it had to do with the value of unexpected behavior: supposedly, if an individual exhibits eccentric or irrational-seeming behavior, it makes it harder for predators to predict what they're going to do and therefore track them down. And then a preference for individuals who are capable of unexpected behavior gets translated, so to speak, into a sense of humor.
Man, I had to grade so many essays about this.
—AJD
The birdsong point is a good one -- whatever people use to explain the evolution of communication will probably play a role here. But maybe some kind of drift / fortuitious emergence story is right for the evolution of communication.
This handicap stuff doesn't impress me that much. Why are some handicaps (singing a lot) attractive while others (being lame) are unattractive? If you can survive while being lame, you're probably of pretty good genetic stock.
So, I agree with your objections to the handicap analysis: why should some handicaps be selected for but not others? Beyond which, it's always seemed to me to be somewhat fishy that an individual with a handicap and extraordinary survival skills should, in the long run, have more reproductive success than someone with no handicap and slightly above-average survival skills, which is what this analysis seems to require; shouldn't the handicap and the extraordinary fitness cancel each other out? But be aware that it's not just art and music in humans whose evolution you're questioning by this; lots of sexually-selected traits are typically analyzed as fitness-indicating handicaps. I think peacock tails are in this category, for instance: they're heavy to carry around, and require a large investment of energy to maintain, so it seems like they should be fitness-reducing.
I guess an alternative explanation of peacock tails is as a secondary index of fitness. That is, if a well-nourished bird will have more lustrous feathers than a poorly-nourished bird, there's evolutionary motivation for a peahen to use feather shininess as a criterion in choosing a mate: feather luster isn't adaptive, but initially if you choose shiny-feathered mates you'll end up with mates with other adaptive qualities. But then sexual selection can get carried away with itself and amplify the selection pressure for feather luster (and other fanciness) to the point that even when it's no longer correlated with fitness, mate preferences are enough to keep it going. Perhaps art and music can be analyzed in an analogous way?
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