Puberty and intelligence

There is clearly a link between intelligence and puberty/speed of maturity. (I have been thinking about this because of a post on One STDV’s blog.)

In no other animal species do the young take so long to mature as do human children.

Between human races, blacks mature faster than whites who mature faster than Asians and that happens to match the ranking of the races’ average IQs.

Girls mature faster than boys and they enter puberty before boys. I believe that this explains why adult men score about four points higher on IQ tests than adult women. I also believe this at least partially explains why men are better at math than women and why Asians are better at math than whites. Late puberty seems to be especially beneficial for development of mathematical ability.

But what of the fact that children have been maturing faster? There has been much written about the “problem” of girls entering puberty earlier than ever. The same thing has probably been happening for boys, but it’s just harder to measure in boys because there’s no clear demarcation as there is for girls (age of first menses). Based on what I wrote in the previous paragraphs, this trend would suggest that people are getting less intelligent, but the Flynn effect has found just the opposite. A reasonable hypothesis is that the Flynn effect and earlier puberty are both caused by the same environmental factor, which is higher calorie diets which cause both the brain and the body to grow bigger and faster. The two effects partially cancel each other out, but the benefits of the brain growing bigger and faster earlier outweighs the detriment of early puberty.

Now, if the above is true, then we ought to be able to significantly increase people’s IQ if we can delay the onset of puberty without depriving them of calories and nutrition. Is this the reason why some ancient societies used to castrate young males? Were eunuchs better at their intended positions because they were smarter?

Comments

[PD]

There are some hormonal treatments that delay puberty; they're mostly used for adolescents with gender identity disorders, to give them more time to deal with various issues without resorting to the permanence of surgery.

There's also intense athletic activity for girls. I wonder if female gymnasts ever have puberty-delaying treatment, or does the training suffice?

I wonder if you could make a short girl taller by delaying puberty?

[nooffensebut]

A few points. One, puberty is measured by Tanner stages, and both girls and boys leave the first stage by having some pubic hair, so it is not that subjective for boys. Two, there are physical differences between male and female brains, such as degree of symmetry, so I would be reluctant to chalk differences up to mere timing rather than the nature of the hormone milieu. Three, I would have to guess that African-American female average IQ would have greatly accelerated upward as of late due to their remarkable, uh, nutritional advancement. Their caloric intake has increased so much that a study a few years ago found they were getting shorter probably from premature bone-plate fusion.

[T]

Interesting connection with the eunuchs. I have been wondering about masculinity in nerds. In some ways they seem to be hyper-masculine but in other ways they seem to be more normal or even below average. My theory is that nerds get an extreme dose of masculinizing hormones (which may even include estrogen in the pre-natal environment) but that their hormone levels are lower after initial development. Thus they get the rational and analytical aspects of maleness that are common to men of all ages, but are a bit short on aspects associated with young adulthood.

[Johnson]

This entire post reminds me of the sci-fi series *Kyle XY* Kyle was grown in a vat and they prolonged his gestation in order to increase his intelligence.

At one point in the series it's explained that Albert Einstein was a late birth and that the extra time he spent in the womb may have sparked his high IQ. I've never checked to see if, in fact Einstein was a late birth or not.

Anyway, that's what your post made me think of.

[cannotwest]

Quite original and insightful comment by T. I rarely encounter such comments.

[J1]

"Were eunuchs better at their intended positions because they were smarter?"

I want to be smart, but not that bad.

[Linda]

"A reasonable hypothesis is that the Flynn effect and earlier puberty are both caused by the same environmental factor, which is higher calorie diets which cause both the brain and the body to grow bigger and faster."

I've been trying to tell you (and others here) that the Flynn Effect is real biological increase in intelligence and not some artificial rise in test scores caused by test sophistication since I first started posting here. Glad you've finally seen the light. :-)

Now how many more years until you agree with me that there is a correlation between IQ and income among college grads?

A word to the wise. If you want to know what Half Sigma will believe after a few more years of study, just read my posts. :-)

[Alex]

You're confusing correlation with causation. A correlation can point to a causal relationship, but it can also suggest a common cause. I think that there is a certain genotype that causes both mathematical development and late puberty. In that case, puberty has no impact on mathematical ability or vice versa.

Can we think of any way of testing what way the causality points?

[Peter]

"puberty is measured by Tanner stages, and both girls and boys leave the first stage by having some pubic hair"

You cannot begin to imagine how hard it is for me to avoid making a wholly inappropriate reply.

[Mack]

Recent evidence suggests that BMI is correlated to the onset of menarche - this is hypothesized to be a significant element of why black girls in the US reach menarche early. People in the developing world generally reach puberty later than westerners - regardless of race.

I think attributing onset of puberty to have something to do with IQ isn't aligned with the facts.

[Mild Speculation]

I agree with Alex. An evolutionary environment that requires speed and strength but not complex, abstract, or future-oriented thought will favor both earlier puberty and lower IQ (or at least higher IQ will not be as valued as in different, mire agricultural environments).

Also, people who excel in a certain area will focus on further specialization in that area at te expense of other things... For example smart kids who suck at sports will naturally spend more time in nerdy pursuits, and vice versa.

[Jack]

Delaying puberty in boys would probably improve their academic performance between 12-15. Delaying puberty in girls would give fathers more time to get used to them growing up.

Of course I have no idea how this would be done.

[Simon]

To add evidence to Halfsigma's brave hypothesis.

http://www.gnxp.com/blog/2007/04/intercourse-and-intelligence.php

Part of the reason for later intercourse among people with high iqs would be greater awareness of consequences (which is probably from higher anxiety as people generally get over it) and more adult supervision from more conscientious parents.

But it's quite possible that later intercourse among high iq adolescents is in part caused by later puberty.

[Steve Johnson]

"Were eunuchs better at their intended positions because they were smarter?"

Eunuchs were better at their intended positions because they didn't have offspring to favor (administrators) or the ability to cuckold the Sultan (harem guards). I've never read anything suggesting that the benefit to being without testicles is increased intelligence(!?).

[Genius]

Puberty has been starting at younger and younger ages, at least over the past few decades. Meanwhile, IQs have been getting higher and higher. Explain.

[Peter A]

"Were eunuchs better at their intended positions because they were smarter?"

The flippant answer would be that if they stopped thinking about sex as much as the average male they now had 90% more of their day to do productive things.

The non-flippant answer is to ask whether there is any evidence that eunuchs were better at their intended position. The list of accomplished eunuchs doesn't seem to be very long, even in Chinese history. Loss of testosterone pretty closely correlates with loss of ambition so eunuchs might be good at routine tasks and administration, but not much else.

[SM]

Within developmental psychology the extension of the prepubescent stage, the evolution of "childhood" as it were, is related to an increase in neocortical ratio and so greater intelligence and thus contributed to the homo sapiens dominance over other species.

I agree, it would be interesting to see if the timing of developmental stages correlated with IQ. But I would hypothesise a negative correlation, as malnutrition = lower IQ + delayed puberty.

[Tanizaki]

"At one point in the series it's explained that Albert Einstein was a late birth and that the extra time he spent in the womb may have sparked his high IQ. I've never checked to see if, in fact Einstein was a late birth or not."

This is one of those Einstein myths. It usually goes that he was a month past due. No biography of Einstein suggests that his gestation was anything but normal length.

[John]

"Can we think of any way of testing what way the causality points?"

Find a nice island somewhere. Get some volunteers, all IQ 120+. Let them have kids. Anyone whose IQ is less than 120 gets booted off the island. Raise the IQ limit by a point every 10 years. Come back in 500 years, and see when people start puberty.

Anyone want to fund me?

[ATC]

Whatever makes smart people smarter is already measurable and obvious well before puberty.

But if delaying puberty for the idiocracy would make them less impulsive and self-assured, I'd be all for it.

[RT]

“Between human races, blacks mature faster than whites who mature faster than Asians and that happens to match the ranking of the races’ average IQs.”

HS, it’s more complicated than “Rushton’s Rule of Three.” While I think he is basically correct, sometimes Rushton strikes me as a little bit sloppy and sometimes tries too hard to fit data into his scheme. Back in college (late 90s) I was doing some research in the field of auxology (human growth) to assess economic living standards in various historical periods. From what I found in the literature, including Evelyth and Tanner’s (the Tanner mentioned above by another commenter) “Worldwide Variation in Human Growth, 2nd Ed.,” it does appear that under comparable nutritional conditions (and sometimes even without them) Africans mature faster than Europeans dentally, skeletally, sexually, and in motor development. On the other hand, with East Asians and Europeans, it’s a little more complicated than that. Generally, East Asians lag Europeans up until about age 4, then draw even and remain on a similar developmental trajectory until around age 10, than develop faster, especially compared to Northern Europeans (who develop slower than S. Europeans, even when inhabiting the same country – e.g., Australia). East Asians actually finish their dental and skeletal development earlier than whites under similar first world living conditions, start their pubertal growth spurt earlier and East Asian girls have an earlier average age of menarche.

[Anony]

"There's also intense athletic activity for girls. I wonder if female gymnasts ever have puberty-delaying treatment, or does the training suffice?"

The training suffices. Growing up I was really involved with both swimming and distance running/track, and I didn't hit puberty until I was 15. Of course my athletic performance diminished a little once I did finally mature.

I've heard that female gymnasts often don't hit puberty until they are 18 or 19.

[tmmm]

Another little bit related question is how circumcision affects intelligence. Does it somehow repress sexuality so people will concentrate on other things ? Can this explain why so many scientists have been Jews?

I have understood that circumcision was norm in US past, but nowdays it is not so common anymore. On the other hand, in Europe it is really rare, except for Jews and Moslims.

[anonymous]

eunuchs were "better" at their positions because you could be sure they were not going to use said position to let in millions of third world barbarians in order to benefit their own children

[Jack]

Most athletic girl in my high school probably hit puberty at 14 or 15 or so. She was always a cool tomboyish chick, til 11th grade started. Then it was like, wow, not bad...

[jeff]

Surely anyone who has worked in an office that is high in IQ and also worked in an average environment has noted that the men in the average office are far more masculine than those in the high IQ office. Also, the women in the average IQ office tend to put out like crazy. Intelligence is linked to sexuality. No doubt about it. My best students were, more often than not, less physically developed than the average students.

[nebbish]

"men in the average office are far more masculine than those in the high IQ office."

I'm not so sure this is true. Investment bankers are noted for aggressive, masculine behavior and typically possess high IQ's and elite credentials. Granted, they're not as smart on average as physics Ph.D.'s (other than the quants who are physics Ph.D.'s), but they are definitely higher IQ than workers in your typical office environment.

[namae nanka]

http://www.boysadrift.com/2007Giedd.pdf

http://www.msnbc.msn.com/id/35332881/ns/health-childrens_health/t/puberty-gap-obesity-splits-boys-girls/

I can't find the paper now, but testosterone's relation to IQ was: lower T boys(before puberty) were both above average and below average.

[The Undiscovered Jew]

Regarding recent changes in human development, has anyone notice white women are a hell of a lot better looking than they were even 70 years ago?

It's already been demonstrated (even after adjusting for the rise in obesity) that bust sizes have increased substantially over past decades.

And if you look at photos of white women, even actresses and models, you'll notice that white women were very bland looking decades ago.

It seems white women have gotten much hotter for some reason.

[HS: I always it assumed it was changing styles (who gets promoted as an actress and what hairstyle and clothes they wear). ]

[jeff]

"Investment bankers are noted for aggressive, masculine behavior and typically possess high IQ's and elite credentials."

A few points:
1. Investment bankers may be exceptional in that they hold both intelligence and strong masculinity
2. The IBs I know are very smart and not very masculine.
3. I am defining masculine as physically imposing and with a very large square jaw. I think this physical aspect of masculinity is separate from mental aggression and attitude to some degree. In business, Bill Gates an obvious low-normal T man, is very aggressive. I see aggressivity as a personality trait that may not always be hormonal in nature. There are tons of super aggressive women who have lower T than men.

All I know is that when I go to Texas, I am small and weak. When I go to the office in Chicago, I am a beast among weenies. My brother recently graduated law school (job within 60 days!) and he commented that nearly all of the men in the program were pussies. I had the same feeling in b-school.

[huge]

the eunuchs were certainly bigger, physically ... cause their HGH production was out of whack ... it's an interesting idea

[huge]

I think mostly eunuchs were attractive to important men cause (a) they won't screw your wife or (b) screw you to help their own children

[The Undiscovered Jew]

"It seems white women have gotten much hotter for some reason.

[HS: I always it assumed it was changing styles (who gets promoted as an actress and what hairstyle and clothes they wear). ]

Posted by: The Undiscovered Jew | August 21, 2011 at 11:14 PM"

The changes go beyond Hollywood fashion changes.

White women on average have obviously have become much hotter than they were prior to the 1970s. Just look at old photos of American women at the beach before 1960 and women today or old photo albums of family members and you'll notice that white women were pretty bland looking up until the 1970's-1980's.

I remember reading a copy of Joe Queenan's book Balsimic Dreams and recall how Queenan noted women were amazingly flatchested even in the 1970's. And Balsimic Dreams was written in the late 90's and bust sizes have only grown larger since then, even after adjusting for obesity.

But the changes (for the better) in white women aren't limited to breasts. They're just much hotter than ever for some reason.

Old swimsuit models didn't look nearly as perfect as this 2011 SI swimsuit model:

http://www.youtube.com/watch?v=Q1woPPSQSDI

Look at early Playboy era photo shoots and you can tell even early playmates wouldn't be considered to be in the top 10% by todays standards.

So something has changed.

Interestingly, guys still look the same as they always have except white men are now taller than ever.

[Felix]

while eunuchs didn't have children, they might have tried to push the careers of their brothers, nephews etc

or perhaps this was addressed by raising the eunuchs separately, so that they didn't develop family ties?

the above is pure speculation, and I'd appreciate any informed comment

[hbd chick]

looks like (european) boys have been hitting puberty at younger and younger ages over the last one or two hundred years or so as well:

A Secular Trend toward Earlier Male Sexual Maturity: Evidence from Shifting Ages of Male Young Adult Mortality

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0014826#pone-0014826-g002

[Anonlicious]

You know, I've noticed this trend among friends / family but could never find a study to back it up.

I personally went through precocious puberty (menarche before age 8) and my visuospatial intelligence is much lower than that of my female relatives who entered puberty in their mid-teens.

That's also why I'm the shortest person in my extended family. It's not an old wives' tale.

Perhaps the late puberty = high IQ correlation partially explains the "skinny nerd" stereotype, at least in women?