This was inspired by a response in the “what’s wrong with polygamy?” thread. It was postulated that evolving human intelligence made competition for mates more deadly between males, favoring monogamy. I’m not sure I buy this, but it raises a related question.
Is intelligence favored by sexual selection among humans? That is, do females have a greater tendency to choose more intelligent mates? (Or, conversely, do males have such a tendency when choosing women?)
My observations tend to suggest the following:
Women of average intelligence generally avoid men who are of less than average intelligence.
Men of average intelligence avoid women only of very low intelligence.
Women of average intelligence are indifferent to men of above average intelligence. (Though there may be an indirect effect in that intelligent men can obtain material and social success that is attractive to women. But when less intelligent men and more intelligent men both have these successes they seem to be roughly equally attractive to women, implying that it is not the intelligence per se that is attractive)
Men of average intelligence avoid women of very high intelligence. (Probably because they feel threatened. This could be an effect of more modern societies and may or may not apply to our prehistorical ancestors)
The above statements are not absolute, obviously, and assume the multitude of other factors people look at in each other are equal.
Is this borne out by others’ impressions? It would imply that sexual selection in humans tends on average to favor the status quo more than a maximizing of intelligence - or at least that the pressure to increase intelligence is fairly small; we would have to look to environmental pressures or indirect mechanisms of sexual selection for the origin of intelligence.
I agree that intelligence is favored, at leasst early on. In another thread, I repeated the observation that human intelligence is a runaway sexual characteristic like enormous Irish Elk horns or the very long tails on some birds. Once a creature can put an edge on a rock and make fire, he is the Crown of Creation. There is no reason to evolve farther. This is evidenced by the 700,000 year technological plateau that Homo erectus experienced.
But for some reason, the more dynamic intelligence shown by the very early humans as they Homo sapiensed themselves out of Homo erectus stock must have had some sexual attraction to the opposite sex and was favored. The extra smarts weren’t necessary, as evidienced by the successful Homo erectus, but it must have attracted the cavebabes and caveguys. That is what counted.
(Jois once described a likely scenario of a bunch of cave women showering affection on a Lower Pleistocene Bill Gates look-a-like.)
I always thought manogamy was kind of unnatural, as most mammals have several mates throughout their lifetime. I think the idea has been incredibally ingrained in society (mostly by organized religion, I suspect) to prevent the spread of VD.
I know the first thing about Genetics, but I don’t know the second or third, so please forgive my naivete. But I’m just wondering, how well established is it that intelligence is a genetic trait?
How well established is it that intelligence has evolved at all? I mean in maybe the last 5000 years or so. Or even longer.
I’m serious. And definately not a creationist.
Plato was pretty smart, right?
Peace,
mangeorge
A former workmate of mine summed this thread up well:
“Long after you’ve fucked her, you have to talk to her.”
This clearly proves that we do indeed select for intelligence that is compatible with our own. What’s the point of marrying someone on the basis of physical attraction if you cringe every time they open their mouth?
Any type of meaningful evolution would not be observed in 5000 years. Any effects in that time are due to better diet, better environment (I would say better teaching but that’s a whole other country), and “shoulders of giants” effect.
Intelligence has at least some genetic component. Some animal mutants (Drosophila CREB for one, another mouse mutant with an increased level of the NMDA receptor) learn better. Many, many, many single gene mutations cause a decrease in learning (Fragile X = 10% of male mental retardation, Rett syndrome, mitochondrial disorders, many metabolic disorders, etc.) 'Course phenotype = genotype + environment.
The question to ask is “What is the selective pressure for greater intelligence?” I mean something is pushing us towards bigger head sizes such that childbirth is often a life risking ordeal. Why didn’t we go the way of cockroaches or bacteria? – they have better survival skills in general than we do. It is maybe the whole elk-horn thing, but many animals have enormous capacity for understanding and memory (elephants, parrots, chimps, gorillas all have large memories).
I like the theory that conciousness is tied to verbal language. This can be sexually selected for easily – look at songbirds’ complicated mating calls as a precursor perhaps. I mean really how many steps is it from a grunt to “How ya doing?”
Intelligent people tend to make more money. Money is one hell of an aphrodisiac. They draw more than their fair share of choices for mates.
The few of us that are in professions that dont pay well, but are considered intelligent also get more possible mate choices that we should. e.g. Professors, artists, etc.
As a professor myself, I have been suprised at the number of students who have come on to me sexually. I have been REALLY suprised by the fact that none of them were in any of my classes. (They were in my dept. but not in my class.) So that they were not doing it for the grade. Since I am not an adonis, I have to asume that they were turned on by my intelligence. (It sure wasn’t my bankroll!)
Sure, sexual selection in humans operates on intelligence (at least as far as I can tell). But it also operates on many other factors too. Also, measuring intelligence isn’t all that easy: one person may think I’m a hideously intelligent guy :), but another may think I’m a complete idiot :(.
Don’t forget that intelligence has an impact on fitness beyond attractiveness to potential mates, it also influences survival (although not as much in modern times: I’m thinking prehistorically here).
In The Third Chimpanzee Jared Diamond lists correlation coefficients for a variety of characteristics: e.g. religion, ethnic background, race, age, and political views have coefficients of around +0.9, while personality traits such as introversion/extroversion and measures of IQ tend to have coefficients of around +0.4.
I disagree completely; I think monogamy is best explained as a trait that aids in raising young. It is much more difficult to raise young with just the mother working at it than it is to raise young with both members of the mating pair providing care. Most monogamous species (mostly birds, but also some mammals) have young that require long-term parental care, which tends to be better provided by a cooperating pair than by just the mother. Humans have young that require exceptionally long term and very intense parental care.
Sexual selection is selectivity in mate choice, it can be considered a subset of natural selection.