Is Intelligence In Humans Still Being Selected For?

My understanding is that the reason we went from being a bunch of dumb ape-like creatures in the past to the intelligent creatures we are today is because intelligence was somehow selected for in our past- either by natural selection or by sexual selection. Is intelligence still being selected for today?

Is there any evidence that people who have above average intelligence have more children or have sex more frequently than those who are just average or below average??


Unless you wish to claim that one sex is more intelligent than the other, you can forget about sexual selection being involved. And you can also forget about the “having more sex” bit, since simply having sex is irrelevant in an evolutionary context.

It is unlikely that higher intelligence (however you choose to define it) correlates to more children. There is a reverse correlation between education and family size - that is, the more education one has, the fewer children one is likely to have (see this graph [.pdf document] titled Women’s education and family size in selected countries). If one wishes to then correlate intelligence to education, then it would certainly appear that intelligence is not being selected for in an evolutionary sense. Being a brainiac is not necessary for survival, and never has been. Being “smart enough” is quite sufficient, so I doubt there is any significant evolutionary pressure to become more intelligent. There are, perhaps, societal pressures to that end, however.

Most of the studies I’ve seen indicate that the average intelligence level of the human race has been dropping in the past century or so. A lot of these studies were presented by people trying to do school reforms, so I wouldn’t exactly call them unbiased, but they may be right.

There was a fairly interesting show on the discovery channel a while back (don’t remember the title, sorry) that basically claimed that before the modern era, earth was a “planet of the apes” for a while. There were a large number of ape-like species, among which were our ancestors. Then, something happened to the environment, causing a bunch of evolutionary branches to fork out, and many species died off. Out of that mess came what we now consider to be our human ancestors. From the looks of things, intelligence was not the major deciding factor, as it developed later. These theories were very controversial, since until then everyone assumed (such as your post does) that the thing that seperated us from the apes was our intelligence. The current theories apparently place the development of intelligence much later in our evolution.

I was tempted to respond with something like, “You wouldn’t want to breed with a stupid person, would you?” as an argument that intelligence is still being selected for, i.e., the real jerks have fewer successful matings, thus slowly raising the bar. But then I realized that while intelligence is admired, people tend to choose mates who are on a similar level of intelligence to their own, be that high or low. So I guess I’d have to agree with Darwin’s Finch, that:

This isn’t great debates and I am not in expert in this area so I should stay out of this thread…

However… :smiley:

I would think that mate selection is primarily driven by physical attributes for both sexes.

Intelligence has some value in that if you take identical people but one is more intelligent he will have more mating opportunities.


If you take these same people and put the intelligent one in a less attractive body and the not-as-intelligent one in a more attractive body (in equal ‘proportional’ increases for attractiveness/IQ) then the more attractive person will get much more mating opportunities than the smarter one.

This matches my experience I have seen among family/friends/acquaintances I’ve known.

So, IMO, intelligence is selected for but it is not the primary or probably not even the secondary factor.

Honestly…how many people do you know that when they are being set up will ask “How smart is he/she?” as their first question? 99% of the time he/she will ask about physical attributes first. Intelligence is just a bonus.

Evolution doesn’t say that one seeks out a partner one finds attractive because of intelligence, or big bright feathers, or whatever.

That happens, but all evolution says is that you mate with someone who managed to stay alive to get to mating age.

If dumb people are more likely to die before they’re old enough to have kids, then natural selection is selecting for intelligence.

There is a difference between being “dumb” and being of “average” intelligence, of course. Intelligence can only be said to be selected for if those of higher intelligence have a greater likelihood of producing offspring than the rest of the population.

Just about the only thing being selected* for these days is poverty. And that’s more of a social condition than a physical (genetic) one.

It’s interesting that our species is the only one “smart” enough to know how to REDUCE the number of offspring we have. And our affluent society makes more children often a burden rather than an asset. One could argue, perhaps, that intellegent people are more likely to use birth control and to use it effectively.

When a population is as successful as we have been, and is expanding w/o any real natural forces constraining that growth, the polualtion tends to be fairly static in terms of evolution.

*“selected for” meaning having more offspring than the average.

I forgot. The LDSers and similar religions have the whole evolution thing figured out, obviously.:slight_smile:

The impression I get–and it’s just an impression–is that these days less intelligent people are having more children than more intelligent people.

If this is the case, it could be due to these factors:

  1. Less intelligent people have beliefs which compel them to have larger families and/or to avoid using birth control and/or tp forgo abortion.
  2. More intelligent people are more competent in using birth control.

Plainly speaking from personal experience - I’ve reached middle age and have no children, largely because I was never selected by women. Seriously. I wouldn’t say I’m Isaac Newton re-incarnate, but I am better educated, though not necessarily sharper, than the average bird.

The real problem was that I was (am) skinny, and I spent most of my “peak selection” years broke (i.e. in school). On the few occasions I could actually engage a female in conversation (with a skinny poor guy), they said they felt “intimidated”, even though I always deflected the conversation away from myself, never “showed off”, and never ridiculed. Or else they said I was “like a brother”. Instead, they’d go for dumb hot guys with money and I ended up home alone.

I finally managed to talk someone into marrying me, but of course it was after she’d been disillusioned by her rich hottie. And a little late for reproducing … believe me - I’d love to have about 6 kids.

This is a fairly odd thread, but here I go…

To answer the original OP, Darwin believed there was “natural selection” (ie, fitting into the environment and beating horns together for access to mates) and “female selection” (“my, you have a pretty tail”). It is hard to see how intelligence would be selected for, since, all things being equal, people of similar intelligence (formed by background…see below) would be “forced” to largely select only each other due to class/caste structures, etc.

Regarding the idea that people are getting “dumber”, some of the school reformers base this aptitude testing but those drops are due to more people taking those tests now for college entrance than in the past. For IQ scores, there is something called the Flynn Effect (you can goggle for the term ) which is that IQ scores have been rising between the generations much faster than hereditary theory can explain.

Overall, much of the “oh mi god, the dumb and poor are breeding too fast!” thinking in the country is closely related to the Charles Murray, et al, wacko theories about race and IQ, or fears of immigrants ruining our precious anglo culture.

This is a topic that has been debated since Darwin’s time. It seems to me that within the next 100 or 200 years that our genome will be subject to so much technological tinkering (assuming that modern civilization continues) that natural or sexual selection will no longer determine the limits of human genetic change.

I’d just like to point out that the people most frequently beaten in high school, college, and other situations where people beat people are, quite frequently, the most intelligent. Nerds, to put it bluntly.
Just an obeservation, I’m sure it has no bearing on THIS situation at all.

In today’s highly technological society, what with people having to drive cars, talk on cell phones, and chew gum at the same time, stupid people tend to die before they have a chance to breed excessively.

I believe Larry Niven called this phenomenon “evolution in action.”


To underscore Darwin’s Finch’s comment about being sufficiently smart, we might as well salute those fine individuals who didn’t make the cut.

I’d drop this generalization. Having beliefs (I’m assuming you mean religious beliefs) that lead one to reject birth control and abortion are not at all good indicators of relative intelligence. Smart people get more abortions? I doubt it.:dubious:

Quoth Darwin’s Finch:

Care to elaborate on this? It seems to me quite plausible to consider a population where the males are preferentially attracted to intelligent females, and the females are preferentially attracted to intelligent males. You might then end up with many smart people breeding with other smart people, some dumb people breeding with smart people, and very few dumb people breeding with other dumb people, such that smart people (of either gender) breed more on average than dumb people. Presto, sexual selection.

Now, I’m not going to claim that this is, in fact, the situation with humans, but it doesn’t require a difference in intelligence of the sexes.

Son of a…

I had a response typed out, tried to preview it…and the Board ate it.

So, let me summarize: sexual selection is not a simple matter of mating based on personal preference. It specifically refers to selection by one sex of traits possessed by the other. Typically, it is the females that do the choosing, and the males who get the adornments to either compete with one another, or to directly woo the females. In situations where the males choose, the females are similarly adorned (as in pipefish). The net effect is that those traits which are selected by the opposite sex tend to be accentuated.

For intelligence to be the product of (or at least be heavily influenced by) sexual selection, males and females would essentially have to “show off” their intelligence to one another before mating occurs. While it may be hypothetically possible for such to occur, in practice it doesn’t. At least not in statistically significant numbers.

Even among humans, females are likely to get the final say in terms of mate selection, since they bear the bulk of the cost of reproduction. Thus, females are still likely to be more selective than males, which would tend to incur, if not accentuate, differences between the sexes.

Ultimately, though, since intelligence has many more uses than simply attracting mates, it would be difficult (if not impossible) to make a case for it falling under the limited purview of sexual selection.

Geoffrey Miller makes the case the human intelligence developed as a result of runaway sexual selection in his book ‘The Mating Mind’-