How minimal is our intelligence?

by on December 19, 2012 at 12:07 pm in History, Science | Permalink

From a longer post by Douglas Reay, this is all worth a good ponder:

Q is polygenetic, meaning that many different genes are relevant to a person’s potential maximum IQ.  (Note: there are many non-genetic factors that may prevent an individual reaching their potential).   Algernon’s Law suggests that genes affecting IQ that have multiple alleles still common in the human population are likely to have a cost associated with the alleles tending to increase IQ, otherwise they’d have displaced the competing alleles.   In the same way that an animal species that develops the capability to grow a fur coat in response to cold weather is more advanced than one whose genes strictly determine that it will have a thick fur coat at all times, whether the weather is cold or hot; the polygenetic nature of human IQ gives human populations the ability to adapt and react on the time scale of just a few generations, increasing or decreasing the average IQ of the population as the environment changes to reduce or increase the penalties of particular trade-offs for particular alleles contributing to IQ.   In particular, if the trade-off for some of those alleles is increased energy consumption and we look at a population of humans moving from an environment where calories are the bottleneck on how many offspring can be produced and survive, to an environment where calories are more easily available, then we might expect to see something similar to the Flynn effect.

For the pointer I thank Michelle Dawson.  Here are some not totally unrelated remarks from James Flynn.

ad*m December 19, 2012 at 1:31 pm

So different human populations have different adaptation rates for IQ. In other words some populations can change their IQ, others cannot.

KevinH December 19, 2012 at 3:00 pm

I’d point out that this also has a totally rational and fairly simple mechanism by accounting for pre-natal diets of the mother. Nutritional supplements to pregant women have been shown by the development literature to have an affect on child behavior and IQ later in life.

Bryan Willman December 19, 2012 at 3:02 pm

In other words, if the “cost” of energy becomes very low (food is easy to get/cheap) then intelligence will be “cheaper” and should be expected to increase over time, assuming it confers competitive/reproductive advantage.

Over a period of generations, IQ would improve more slowly or not at all in whole populations that are badly foodly constrained. This could be tested, though of course it’s hard to sort out the population effects from the simple brutality effect that starving children interferes with their development.

One wonders too about opportunity – in the 1st world today there is a generally large supply of opportunities to make good competitive use of intelligence. But one could imagine a world where it didn’t much matter.

JWatts December 19, 2012 at 3:41 pm

“the human body could use to create Docosahexaenoic acid, which is a fatty acid required for human brain development. Originally humans got this from fish living in the lakes and rivers of central Africa. However, about 80,000 years ago, we developed a gene that let us synthesise the same acid from other sources”

This is a fascinating fact that I was unaware. Without that particular mutation, humans probably couldn’t have become widespread or populous. Civilization might not have developed at all depending on how much fish was required.

Nathan W December 20, 2012 at 8:15 am

Agreed, fascinating. I often wondered how eating fish was supposed to be a key step, but then non-fish eaters don’g seem to have a problem with neural development, etc.

Matt December 19, 2012 at 5:06 pm

If energy availability has a major effect, then obesity via energetic disregulation rather than excess intake is relevant.

In the same way that an animal species that develops the capability to grow a fur coat in response to cold weather is more advanced than one whose genes strictly determine that it will have a thick fur coat at all times, whether the weather is cold or hot; the polygenetic nature of human IQ gives human populations the ability to adapt and react on the time scale of just a few generations, increasing or decreasing the average IQ of the population as the environment changes to reduce or increase the penalties of particular trade-offs for particular alleles contributing to IQ.

Those kind of animals with the potential to vary strongly from thick fur to hairless are rare, actually absent. Competitive disadvantage (or null advantage while being more complex to evolve)

Be interesting to see if any animals models, e.g. domestic dogs, pigs, mice, validate any of this. I think mice even would not validate this.

My general opinion is, to quote John Hawks blog

http://johnhawks.net/weblog/reviews/brain/size/brain_size_molecular_review_plos_2007.html

“It’s total nonsense. By the same logic, if hunters leave piles of sugar beets out for the deer for a couple thousand years, then deer should evolve bigger brains.
The fallacy here is a confusion about fitness versus selection. It is certainly true that natural selection increases a population’s mean fitness. But like any other phenotype, fitness may be increased by changes in the environment. A constantly replenished pile of sugar beets increases the fitness of the local deer. They leave more offspring, and their population grows.
But that is just what fitness is: an increase in the rate of intrinsic population growth. Under the sugar beet diet, large, expensive-brained deer survive better. But so do small-brained, stupid deer. No correlation between brains and sugar beets means no selection. Hence, a never-ending supply of sugar beets will certainly get you more deer (which is the hunters’ goal) but not smarter deer.”

Selective forces, unlike human forces (e.g. Tyler), do not push in the direction of “oh more energy, so let’s spend it on these nice, wonderful, hedonic, liberating, empowering, world knowing things” they push to the direction of “There is more energy so let’s spend it on reproduction”. That is the basis of natural selection, period.

An organism may be selected to respond to sudden increases in available energy by spending more energy on brainpower, but only if that actually has selective advantage over just spending the energy on doing the same thing but reproducing more, and I do not think that has ever been the case in the history of the human lineage.

Dick King December 19, 2012 at 7:50 pm

Some people have hypothesized that intelligence is a peacock’s tail. It’s not an insane hypothesis.

http://www.amazon.com/The-Mating-Mind-Sexual-Evolution/dp/038549517X/

-dk

dan1111 December 20, 2012 at 7:20 am

Only the male peafowl has the tail. Insert your joke here, but wouldn’t this hypothesis imply that men should be far more intelligent than women? I don’t see it.

Urso December 20, 2012 at 9:41 am

“Not insane” is hardly a ringing endorsement.

gcochran December 19, 2012 at 8:26 pm

You can easily estimate the rate of change of intelligence: multiply the selection differential by the narrow-sense heritability. The selection differential is the average difference between the population as a whole and those who are the parents of the next generation. What kind of change should we expect over a couple of generations, within a given population? IQ might drop 1 point, with current fertility patterns.

Nathan W December 20, 2012 at 8:23 am

Cockroaches don’t have a very high IQ and they’ll survive for a long time yet.

While the role of intelligence is clearly important in our evolutionary history, I have two problems with the assumption that this will continue to be true: a) in a changing environment, we make surpass a threshold where greater intelligence will make either individuals or societies less fit (I could dream up a dozen potential situations here) and b) what the hell is intelligence anyways? I find the notion of the IQ to be nearly useless because it does a very poor job of accounting for people’s ability to learn and adapt. The type of intelligence that we will need in the future may bear little relationship to any of the sorts of thing showing up on these tests, and the random changing nature of our environment means that we would be silly to think that we will know what constitutes “fitness” in the future, if our collective genius doesn’t kill us all off first.

Dredd December 20, 2012 at 12:40 pm

Ninety Eight percent of the homo sapien genome is microbial, two percent is “human.”

One can readily see why, then, there are a lot of genetic myths floating around the brainosphere.

“Don’t purchase genetic textbooks in used book stores” might be useful advice.

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