This secular decline in testosterone is pretty dramatic. Our best source is A Population-Level Decline In Serum Testosterone Levels In American Men, which finds that from 1987 to 2004, average testosterone declined from 501 ng/dl to 391 ng/dl, with an even more dramatic decline in bioavailable levels of the hormone. That’s about minus 1% per year.

No one knows exactly why this is happening. Some people blame increasing obesity and decreasing tobacco use (wait? Smoking increases testosterone levels? THOSE TV COWBOYS WERE RIGHT ALL ALONG!). Other people have tried to adjust for these and found they don’t explain the entire effect, leading to a host of other theories. Recent scrutiny has focused on the role of feminizing chemicals in the water supply, probably a combination of industrial pollutants and discarded medications; the worst-affected areas are marked by an epidemic of transsexual fish (really).

(A quick aside – since these chemicals are gender-bending fish, frogs, and various other animals, could they be responsible for transgender in humans? This theory seems to still be in crackpot territory, but I don’t know why. Research shows that male-assigned-at-birth children exposed to diethylstilbestrol in the womb are more likely to become transgender than the general population. Other than that, there just seems to be one unpublished paper on the subject. Get to work, scientists!)

Annnnnyway, testosterone has been found to correlate a bit with violent crime. In a study of 692 male criminals, Dabbs et al found that those in prison for more violent crimes had higher testosterone than those in prison for nonviolent offenses. It’s hard to say exactly how much higher because they report their testosterone in a different way that doesn’t correlate to anyone else’s – I think part of it is that it’s salivary rather than serum testosterone but it’s still confusing even after I adjust for that. If we use relative rather than absolute, they do mention that 66% of inmates in the upper third of testosterone levels committed violent crimes compared to 46% in the lower third. High-T inmates were twice as likely to be in for murder as low-T inmates. Interestingly, testosterone was the highest risk factor for sex crimes, such as child molestation and (especially) rape – high-T inmates were four times as likely to be in for rape as low-T inmates. On the other hand, low-T inmates were about twice as likely to be in prison for drug offenses.

This “which criminals are worse” study is obviously not as good as an “are high-T people more likely to be criminals at all” study, but I can’t fin any of those with a good sample size. You can read a review of the research here.

According to the population decline study, testosterone levels declined about 110 ng/dL in 15 years. They don’t give me a standard deviation, but from this site I get one a bit less than 200. So testosterone declines by one standard deviation about 25 years? That means that a person in the top third of testosterone levels today would have been in the bottom third fifty years ago. Which – and I realize I’m doing all sorts of horrible things here to cover up my lack of actually useful data – if we extrapolate wildly from the results of these studies, we could sort of justify murder halving in about fifty years by falling testosterone alone.

The first problem with this is that we can’t really use data on prison inmates as representative of the population.

The second problem is that murder has halved in way less than fifty years. It seems to have halved between 1994 and 2004.

The third problem is that crime didn’t start falling until the early 1990s, but testosterone was falling since at least 1987 and probably earlier. This site, which doesn’t cite sources, says testosterone was higher in the 1940s, though they might be confusing that with “in men born in the 1940s, as studied in the 1980s”, which is of uncertain significance. Sperm count has been declining since the 30s, according to an article called Sperm Quality & Quantity Declining, Mounting Evidence Suggests

(it looks like somebody was not quite as virtuous as this Twitter user).

The fourth problem is that there’s contradictory evidence about whether testosterone is even falling at all, according to a a study that looked at the faces of Major League Baseball players of the past 120 years. This sort of makes sense – face width-height ratio is affected by testosterone (one reason women’s faces look different than men’s) and baseball players had standardized photographs taken of them for that time period. They find that, at least based on the face ratios, testosterone was increasing during that period, which would be interesting if it didn’t contradict everybody else. As it is, I suspect it just means baseball players were differently representative of the general population. For example, if baseball requires high testosterone, and scouts became better at selecting the highest-testosterone people over that period, that’d do it. Or if the nature of baseball changed to more of a “power game” rather than a “finesse game” (I think some people have said this) that’d do it too. Or if all baseball players suddenly started taking powerful testosterone-analogue chemicals at some point…hmmmmmmmmm…On the other hand – literally on the hand – we have the digit ratios of Lithuanians over 120 years. Someone in 1880 measured the length of Lithuanians’ fingers – which can be a proxy for testosterone levels – and then the experiment was repeated recently and the results compared. It did find the expected increase in testosterone, though no word on whether that was throughout the entire period or just concentrated in the past couple of years. So this sort of turned out to be a non-problem.

The fifth problem is that crime is dropping in women at the same rate as in men – women never really committed that many crimes, but now they’re committing fewer. Women do have some testosterone, so it’s possible that declining testosterone could affect female violence as well, but it wouldn’t be the first thing I expected. Also, I’m not sure if there are any secular trends in female testosterone levels, though I’d be fascinated to see data.

So overall while I like the approach of this hypothesis, I don’t think it gets the time window right. It would be a nice way to explain a gradual fifty-year decrease in violent crime starting in the 50s and continuing to the present day. Instead, we have a big spike in the 50s and a big drop in the 90s, which were not particularly abnormal in terms of testosterone decline.

This doesn’t really make sense to me. If testosterone is declining, it should cause a decrease in crime. One might argue that testosterone levels have been steadily operating behind the scenes causing very long term declines while other things account for the more visible short-term trends, but that seems like a cop-out.

I’d like to see studies comparing testosterone levels in violent criminals (both male and female) to those in the general population.

Also, we have cemeteries full of millions of dead people from every era of history, all carefully marked with what age they were when they died. Somebody needs to dig some of them up and measure their digit ratios – I assume you can still measure the digit ratio of bones, the overall length is still there. Then we can have a good answer for whether testosterone levels in men (and women) have been declining over time, when it started, and whether it’s been picking up recently. If it has been, the chance that it hasn’t had an important effect on our society worth exploring is pretty much nil.

I know, just once I want to get through an entire blog post without a call for disinterring the dead, but this is important.

That means if we want to use 23andMe irresponsibly, we’ve got to do it ourselves. Luckily I recently figured out how to do this and it is exactly as much fun as you would think.

If you’ve got a 23andMe account, log in, go to your name and picture on the bar on the top, and click on the little inverted triangle to get the drop-down menu. Go to the “Browse Raw Data” option, which will give you the option to go to a gene or an SNP. Now all you have to do is find an SNP you’re interested in (an SNP will look like the letters “rs” followed by a string of numbers) plug it in, and interpret the results.

Your best bet here is SNPedia, a wiki collection of different SNPs. If you want to know, for example, something interesting about your risk of heart disease, you can search “heart disease” and get a list of the most relevant SNPs (in this case, rs2383206, rs10757278, rs2383207, and rs10757274). If you click on the first, you can find on the top right in little colored boxes that someone with (A;A) at this site has normal risk of heart disease, someone with (A;G) 1.4x increased risk, and someone with (G;G) 1.7x increased risk.

In this case my 23andMe results are pretty straightforward – it tells me I am (G;G), which is common enough in white people (see the little colored bars on the left of SNPedia; the CEU bar is Caucasian Europeans). Other times the results require an extra step. For example, SNPedia’s page on rs1801133 offers three choices – (C;C), (C;T), and (T;T), but 23andMe tells me that I have (A;A), which didn’t appear to be an option. The problem here is that 23andMe is giving me the minus strand – if you click to expand your result, it will tell you that (“dbSNP Orientation: minus”). When it gives you the minus strand, you have to manually reverse it to get the plus strand. Remember, A is the reverse of T, and C is the reverse of G. So my (A;A) is their (T;T), and I have 1.5x risk of various cancers.

This doesn’t necessarily bear any relationship to reality, because genetics studies often fail to replicate, and even when they’re right they might only apply to certain populations, and even when they apply to people usually people misinterpret what they mean. That’s part of why the FDA banned 23andMe from doing this, and part of why the word “irresponsible” is right in the title. Even if these SNPs survive the tests of time and replication, they will explain at most a few percent of the variance in complex traits, and any claims otherwise are exaggeration at best and pure hype at worst.

But with that fair warning, here are some of the genes I think are most fun to look up. I cannot disclaimer enough that this is for your own amusement only and unlikely to resemble reality in more than the most tenuous way and if I imply otherwise it is a silly joke.

Rs909525 is linked to the so-called “warrior gene” which I blogged about in the last links roundup. People with the normal four or five repeat version of these gene are less violent than people with the three-repeat version, and people with the two-repeat version are massively overrepresented among violent criminals. See for example this article. Although this SNP isn’t the warrior gene itself, it’s linked to it closely enough to be a good predictor. This is on the X chromosome, so men will only have one copy (I wonder how much of the increased propensity to violence in men this explains). It’s also one of the minus strand ones, so it’ll be the reverse of what SNPedia is telling you. If you’ve got T, you’re normal. If you’ve got C, you’re a “warrior”. I’ve got C, which gives a pretty good upper limit on how much you should trust these SNPs, since I’m about the least violent person you’ll ever meet. But who knows? Maybe I’m just waiting to snap. Post something dumb about race or gender in the open thread one more time, I dare you…

Rs53576 in the OXTR gene is related to the oxytocin receptor, which frequently gets good press as “the cuddle hormone” and “the trust hormone”. Unsurprisingly, the polymorphism is related to emotional warmth, gregariousness versus loneliness, and (intriguingly) ability to pick out conversations in noisy areas. 23andMe reads this one off the plus strand, so your results should directly correspond to SNPedia’s – (G;G) means more empathy and sociability and is present in 50% of the population, anything else means less. I’m (A;G), which I guess explains my generally hateful and misanthropic outlook on life, plus why I can never hear anyone in crowded bars.

Rs4680 is in the COMT gene, which codes for catechol-o-methyltransferase, an enzyme that degrades various chemicals including dopamine. Riffing on the more famous “warrior gene”, somebody with a terrible sense of humor named this one the “worrier gene”. One version seems to produce more anxiety but slightly better memory and attention; the other version seems to produce calm and resiliency but with a little bit worse memory and attention. (A;A) is smart and anxious, (G;G) is dumb and calm, (A;G) is in between. if you check the SNPedia page, you can also find ten zillion studies on which drugs you are slightly more likely to become addicted to. And here’s the 23andMe blog on this polymorphism.

Rs7632287, also in the oxytocin receptor, has been completely proportionally and without any hype declared by the media to be “the divorce gene”. To be fair, this is based on some pretty good Swedish studies finding that women with a certain allele were more often to have reported “marital crisis with the threat of divorce” in the past year (p = 0.003, but the absolute numbers were only 11% of women with one allele vs. 16% of women with the other). This actually sort of checks out, since oxytocin is related to pair bonding. If I’m reading the article right (G;G) is lower divorce risk, (A;A) and (A;G) are higher – but this may only apply to women.

Rs11174811 is in the AVPR1A gene, part of a receptor for a chemical called vasopressin which is very similar to oxytocin. In case you expected men to get away without a divorce gene, this site has been associated with spousal satisfaction in men. Although the paper is extremely cryptic, I think (A;A) or (A;C) means higher spousal satisfaction than (C;C). But if I’m wrong, no problem – another study got the opposite results.

Rs25531 is on the serotonin transporter. Its Overhyped Media Name is “the orchid gene”, on the basis of a theory that children with one allele have higher variance – that is, if they have nice, happy childhoods with plenty of care and support they will bloom to become beautiful orchids, but if they have bad childhoods they will be completely screwed up. The other allele will do moderately well regardless. (T;T) is orchid, (C;C) is moderately fine no matter what. There are rumors going around that 23andMe screwed this one up and nearly everybody is listed as (C;C).

Rs1800955 is in DRD4, a dopamine receptor gene. Its overhyped media name is The Adventure Gene, and supposedly one allele means you’re much more attracted to novelty and adventure. And by “novelty and adventure”, they mean lots and lots of recreational drugs. This one has survived a meta-analytic review. (T;T) is normal, (C;C) is slightly more novelty seeking and prone to drug addiction.

Rs2760118, in a gene producing an obscure enzyme called succinate semialdehyde dehydrogenase, is a nice polymorphism to have. According to this article, it makes you smarter and can be associated with up to fifteen years longer life (warning: impressive result means almost certain failure to replicate). (C;C) or (C;T) means you’re smarter and can expect to live longer; (T;T) better start looking at coffins sooner rather than later.

Rs6311 is not going to let me blame the media for its particular form of hype. The official published scientific paper on it is called “The Secret Ingredient for Social Success of Young Males: A Functional Polymorphism in the 5HT2A Serotonin Receptor Gene”. Boys with (A;A) are less popular than those with (G;G), with (A;G) in between – the effect seems to be partly mediated by rule-breaking behavior, aggression, and number of female friends. Now it kind of looks to me like they’re just taking proxies for popularity here, but maybe that’s just what an (A;A) nerd like me would say. Anyway, at least I have some compensation – the popular (G;G) guys are 3.6x more likely to experience sexual side effects when taking SSRI antidepressants.

Rs6265, known as Val66Met to its friends, is part of the important depression-linked BDNF system. It’s a bit depressing itself, in that it is linked to an ability not to become depressed when subjected to “persistent social defeat”. The majority of whites have (G;G) – the minority with (A;A) or (A;G) are harder to depress, but more introverted and worse at motor skills.

rs41310927 is so cutting-edge it’s not even in SNPedia yet. But these people noticed that a certain version was heavily selected for in certain ethnic groups, especially Chinese, and tried to figure out what those ethnic groups had in common. The answer they came up with was “tonal languages”, so they tested to see if the gene improved ability to detect tones, and sure enough they claimed that in experiments people with a certain allele were better able to distinguish and understand them. Usual caveats apply, but if you want to believe, (G;G) is highest ability to differentiate tones, (A;A) is lowest ability to differentiate tones. (A;G) is in between. Sure enough, I’m (A;A). All you people who tried to teach me Chinese tonology, I FRICKIN’ TOLD YOU ALL OF THE WORDS YOU WERE TELLING ME SOUNDED ALIKE.

All this leaves me a little surprised that there isn’t more scientific study of nerds.

And yet there is not. Typing “nerd” into Google Scholar brings up only a series of papers on desert plants by one Dr. A. Nerd, who must have had a very unpleasant childhood. The field remains strangely unexplored.

“Nerds” seem to share a bunch of seemingly uncorrelated characteristics. They’re generally smart. They’re interested in things like math and science, especially the hard sciences like physics. They’re shy and awkward. They’re some combination of bad at getting social status and not interested in getting social status. They’re especially bad at getting other people to show romantic interest in them. They’re physically unimposing and bad at sports. They don’t get in physical fights and are very unlikely to solve problems with violence. They’re straightedge and less likely to drink or smoke to excess (according to legend, “nerd” derives from “knurd”, ie “drunk” spelled backwards). Sometimes even very specific physical characteristics make the list, like a silly-sounding high-pitched voice.

A scientific study of nerds might begin by asking: why do all of these things go together in the popular imagination, form a single category?

Of these nine classic characteristics, we can imagine people scoring either “nerdy” or “anti-nerdy” on each. If that were true, there’s only a 1/2^9 = 1/512 chance that any given person has all of these characteristics. Our null hypothesis might be that “nerd” is just a made-up category used to describe this totally coincidental group of 1/512th of the population, or those people who are sufficiently close (maybe 6 or 7 out of 9?). Could be.

The other possibility is that in fact these traits are all correlated for some reason, and people who are bad at sports really are more likely to enjoy math, less likely to drink or use violence, et cetera. “Nerd” would then be a natural category, in the same way that, for example, “bird” is a natural category pointing out that animals with feathers are more likely to have wings, beaks, et cetera rather than a totally random distribution of traits. Why would that be?

Have there been nerds across different times and cultures? The term was only coined in the mid-20th century. But Isaac Newton seems to have been a nerd. Whatever else he was, Henry Cavendish was at the very least a nerd. On the other hand, some of the Europeans I’ve talked to say that the experience of nerdiness on their side of the Atlantic is very different from the American experience, so much that it’s hard to interpret them as having a “nerd” concept at all. From my time in Japan, the experience there is different as well.

One can sort of imagine how certain of the correlated characteristics might cause others. Young people who are small and weak and bad at sports might lose social status as a result. People who are good at math might be so transfixed by the mysteries of the universe that things like sports and socializing and dating pale in comparison. People who are very smart might, for the usual neurological reasons, also have high impulse control, explaining the lack of drug use and aggression. People who are bad at social skills might not get invited to sports games and so have no opportunity to improve; they might take up unpopular but solitary pursuits like math as a result.

Or we could take the fun route and go full biodeterminist. The connection to autism and Asperger syndrome is so commonly cited (despite a lack of any real scholarly investigation) as to be cliched. Anyone familiar with the full-fledged syndrome understands it’s something very different from everyday nerdiness, but the possibility that nerdiness is some very mild form or related condition probably shouldn’t be ruled out.

Or we could go a different route. Consider:

In men (but not women) low testosterone is related to increased mathematical intelligence and increased likelihood of being gifted.

Testosterone is associated with extraversion, alone of Big Five characteristics.

Higher testosterone men have higher social status, and the cognitive role of testosterone has been described as “best understood in terms of the search for and maintenance of social status”

As anyone who has watched the controversy over steroid use in professional sports knows, testosterone improves muscle mass and athletic performance.

Men with lower testosterone have lower mating success.

High testosterone is correlated with increased drinking behavior with p < .001. Especially in prison populations, high testosterone is closely linked to violence and aggressive behavior

Men with lower testosterone have higher-pitched voices (the media bills this as Deep Voiced Men Make Bad Mates: Study)

So at least in men, low testosterone seems to cause most of the characteristics associated with nerdhood.

But I’m being unfair. There’s a lot of counterevidence as well.

There are so many conflicting studies on testosterone and intelligence that I despair of getting anything coherent. Many studies show increased testosterone increases intelligence, especially in tasks where men generally outperform women, like spatial rotation (which tends to correlate with math) – for example, see here. I respect this research, but I would naively expect, let’s say, brilliant mathematicians to have lower testosterone than the general population, just based on my stereotypes that testosterone is associated with aggressiveness, popularity, athleticism, etc. I’m not sure how this squares with the data.

Testosterone doesn’t actually make male faces more attractive, according to Testosterone increases perceived dominance but not attractiveness in human males.

Nerds are traditionally viewed as having high libido – think watching pornography. But of course high testosterone is associated with higher libido. I don’t know if there’s a cultural thing going on where nerds have normal-to-low libido but are stereotyped as having high libido to make fun of their lack of romantic success – or even whether the pornography connection is just that nerds are better with computers. I also note with interest that testosterone is said to affect sexual libido but not desire for “sensual touch”, and a lot of people have mentioned how anomalously some of the nerd communities I’m in tend to value cuddling compared to sex relative to the general population.

I could probably find other traditionally nerdy characteristics that correlated negatively with testosterone. For example, acne is associated with higher testosterone levels.

So I don’t think this is the whole picture.

But I still feel like it should be some of the picture. Sex hormones are really complicated – for example, there seem to be different effects from in utero sex hormone exposure compared to pre-pubertal sex hormone exposure compared to pubertal sex hormone exposure, and these aren’t necessarily correlated with each other in the same people. Estrogens can have effects ranging from very similar to testosterone to exactly the opposite. Testosterone is hard to get a good measurement from, especially with the no-fuss salivary measurements I bet most of these studies used, and its effects or lack thereof would depend on lots of stuff like how much of it gets converted to dihydrotestosterone. Also, some hormones have totally different effects if they come in short spikes versus constant gradual release. So there’s a lot of room to improve our understanding of sex hormones and start distinguishing between unlike constructs.

I am reminded of an observation common among transsexuals – and brought up in Ozy’s last post – that there is a distinct cluster of transwomen who have certain very traditionally-considered-male-gendered characteristics and are very nerdy. This seems like another example of some strongly male and strongly female characteristics anomalously going hand in hand.

And what about female nerds? If we’re trying to make this about testosterone, it sounds like they need a separate explanation. Is female nerd a distinct cluster in the same way male nerd is? I don’t know. I don’t, for example, have strong feelings about whether female nerds are more or less attractive/athletic/whatever compared to non-nerdy females.

Mostly I just feel like this field is strangely under-explored. Especially when you consider what the sorts of people who explore fields are like.

There’s this stereotype that the Left believes that human characteristics are socially determined, and therefore mutable. And social problems are easy to fix, through things like education and social services and public awareness campaigns and “calling people out”, and so we have a responsiblity to fix them, thus radically improving society and making life better for everyone.

But the Right (by now I guess the far right) believes human characteristics are biologically determined, and biology is fixed. Therefore we shouldn’t bother trying to improve things, and any attempt is just utopianism or “immanentizing the eschaton” or a shady justification for tyranny and busybodyness.

And I think I reject this whole premise.

See, my terrible lecture on ADHD suggested several reasons for the increasing prevalence of the disease. Of these I remember two: the spiritual desert of modern adolescence, and insufficient iron in the diet. And I remember thinking “Man, I hope it’s the iron one, because that seems a lot easier to fix.”

Society is really hard to change. We figured drug use was “just” a social problem, and it’s obvious how to solve social problems, so we gave kids nice little lessons in school about how you should Just Say No. There were advertisements in sports and video games about how Winners Don’t Do Drugs. And just in case that didn’t work, the cherry on the social engineering sundae was putting all the drug users in jail, where they would have a lot of time to think about what they’d done and be so moved by the prospect of further punishment that they would come clean.

And that is why, even to this day, nobody uses drugs.

On the other hand, biology is gratifyingly easy to change. Sometimes it’s just giving people more iron supplements. But the best example is lead. Banning lead was probably kind of controversial at the time, but in the end some refineries probably had to change their refining process and some gas stations had to put up “UNLEADED” signs and then we were done. And crime dropped like fifty percent in a couple of decades – including many forms of drug abuse.

Saying “Tendency toward drug abuse is primarily determined by fixed brain structure” sounds callous, like you’re abandoning drug abusers to die. But maybe it means you can fight the problem head-on instead of forcing kids to attend more and more useless classes where cartoon animals sing about how happy they are not using cocaine.

What about obesity? We put a lot of social effort into fighting obesity: labeling foods, banning soda machines from school, banning large sodas from New York, programs in schools to promote healthy eating, doctors chewing people out when they gain weight, the profusion of gyms and Weight Watchers programs, and let’s not forget a level of stigma against obese people so strong that I am constantly having to deal with their weight-related suicide attempts. As a result, everyone…keeps gaining weight at exactly the same rate they have been for the past couple decades. Wouldn’t it be nice if increasing obesity was driven at least in part by changes in the intestinal microbiota that we could reverse through careful antibiotic use? Or by trans-fats?

What about poor school performance? From the social angle, we try No Child Left Behind, Common Core Curriculum, stronger teachers’ unions, weaker teachers’ unions, more pay for teachers, less pay for teachers, more prayer in school, banning prayer in school, condemning racism, condemning racism even more, et cetera. But the poorest fifth or so of kids show spectacular cognitive gains from multivitamin supplementation, and doctors continue to tell everyone schools should start later so children can get enough sleep and continue to be totally ignored despite strong evidence in favor.

Even the most politically radioactive biological explanation – genetics – doesn’t seem that scary to me. The more things turn out to be genetic, the more I support universal funding for implantable contraception that allow people to choose when they do or don’t want children – thus breaking the cycle where people too impulsive or confused to use contraception have more children and increase frequency of those undesirable genes. I think I’d have a heck of a lot easier a time changing gene frequency in the population than you would changing people’s locus of control or self-efficacy or whatever, even if I wasn’t allowed to do anything immoral (except by very silly religious standards of “immoral”).

I’m not saying that all problems are purely biological and none are social. But I do worry there’s a consensus that biological things are unfixable but social things are easy – or that social solutions are morally unambiguous but biological solutions necessarily monstrous – and so for any given biological/social breakdown of a problem, we figure we might as well put all our resources into attacking the more tractable social side and dismiss the biological side. I think there’s a sense in which that’s backwards, and in which it’s possible to marry scientific rigor with human compassion for the evils of the world.

This is a forum where people discuss supplements and nootropics. I started looking at it when I was conducting the nootropics forum, assumed it was similar to every other forum that fits that description, and didn’t pay it more attention until today.

Today I looked at it in more depth and discovered their group buys.

The way this works is: people on the forum hear about some exciting new chemical that was found to have promising effects in an experiment, after which researchers say something like “this might be ready for human trials in a couple of years”.

Then everyone pools their money together, pays thousands of dollars to get a research laboratory somewhere to synthesize them a big batch of the chemical, distributes it to everyone in the forum, and they all ingest it and see if they grow wings or a third arm or whatever.

Needless to say this is a terrible idea and they will all probably die of some horrendous disease unknown to medical science. That’s not even in dispute.

But I was raised on science-fiction stories, and one of the most common tropes was some wonder drug being developed and then suppressed by the government. When I was like seven, I read a story about a kid in a science fair who invented a chemical that let people photosynthesize, and the government made him stop because it would destroy the food industry (my childrens’ books were better than yours). The basic structure of the mad scientist genre is small-minded fools delaying a genius in supremely great work. And in a world where the government is trying to put the brakes on the personal genomics revolution and drugs succeed or get ignored for confusing reasons, it’s easy to worry that real life might borrow from some of those tropes.

For example, a research team recently did something that looked like they might sort have reversed aging in rats. The lead researcher says he wants to start human trials soon, but he “is reluctant to forecast how long it will be before the compound might be readily available for use”, the chemical seems to be really expensive to manufacture in sufficient quantities, and the bioethicists will want to have their say about what if rich people can afford it more easily than poor people, and so on and so forth. Overall this doesn’t seem likely to be an exception to the rule that nothing ever makes it to market in less than five or ten years.

Meanwhile, the people on Longecity have already gotten a price tag from a chemical supplier and a couple dozen people willing to be human guinea pigs.

This particular case I am not optimistic about – they seem to be looking not at the precise chemical used in the rat studies but at a cheaper substitute; although as far as I can tell their biochemistry checks out, I feel like if the cheaper substitute worked the original researchers would have used it themselves. And this substitute also seems to be commercially available in some places and no one is aging in reverse. So this will probably be a no-go.

But they’re also working on group buys for a kappa opioid antagonist that someone says might help social motivation and a TrkB agonist that acts as a BDNF-mimetic and appears to treat Alzheimers in a mouse model.

I cannot even come close to endorsing this. The responsible part of me says that it is a terrible terrible idea and they will all come down with exotic cancers and die. It probably is a sweeping condemnation of our government that they haven’t burnt the whole website to the ground and then scattered red tape over the ruins so nothing can grow there again.

But another part of me is full of glee that a random Internet site has just made an entire class of dystopias impossible. If there is a miracle drug out there that makes you super-smart or reverses aging or something, and for some reason like an evil conspiracy or just bad luck it never “made it”, someone on Longecity will have taken it within a week of it first being mentioned online. And if they report that they think it worked, a couple hundred people will figure out hare-brained and probably illegal ways to get some.

I think a good motto for western civilization would be “Our institutions are stupid and our population is insane, but occasionally these two flaws perfectly balance each other out and it’s sort of neat”

I previously asserted crime was stable during that period, pointing out similar murder rates between 1850 New York and London and 1980 New York and London, which I trusted more than (say) burglary rates. But Michael replied with a 2002 study showing that improved medical technology has saved a lot of murder victims and bumped their attackers’ crimes down to attempted murder, meaning the apparent murder rate is artificially low. Correct that, and murder could have increased by 5-10x or more from 1850 to 1980, which would not be too different from the rates in lesser crimes like burglary.

I am still not entirely certain about this. We have good records on attempted murders for the past 30 years or so, and they have been going down along with the murder rate. And it is surprising that the improvement in medical technology so perfectly balances out the increase in violence. But it’s a strong study, and so I will provisionally accept that crime including murder could have risen by 5-10x or more from 1850 to 1980.

But we don’t have to accept that the reason is too much democracy or some sort of wacky political point like that.

I have previously come out as a biodeterminist. I suspect most social influences matter less than anyone thinks and most biological influences matter more than anyone thinks. When I say that, everyone always assumes I’m talking about genes, which is too bad because genes are almost the least interesting aspect of biodeterminism.

Anyone reading this blog probably already knows that lead is very strongly suspected of causing crime. A generation after gasoline was leaded, crime increased by a factor of four; a generation after lead was banned from gasoline, crime decreased by a factor of four. Levels of automobile lead emissions were found to explain 90% of the variability in violent crime in America. States that banned lead more quickly saw crime drop more quickly. Neighborhoods with higher lead levels consistently had higher crime rates. Blood lead levels show a marked inverse correlation with IQ, and a marked direct correlation with criminal history, even when plausible confounders are taken into account. And neuroscientists have known for decades that lead damages parts of the brain normally involved in good decision-making and in impulse control.

Lead levels started rising with the Industrial Revolution and, although in decline, are still far higher than in pre-industrial societies. They are highest in cities and especially in the inner city. They have shown correlation with crime, teenage pregnancy, and many mental disorders.

But like I said, everyone reading this blog probably already knows that. So let me talk about something I just learned last week.

Omega-6 fatty acids.

These are some of those “polyunsaturated fatty acid” things you always hear nutrition geeks talking about. They were pretty rare in human diets until the advent of industrial food processing. Here is a mysterious graph for which I have no source:

Here’s another that comes from Stephan Guyenet:

So suffice it to say that our consumption of these fatty acids has increased a lot. This is not surprising – they are most common in things like the vegetable oil that a bunch of preserved foods have.

The other main kind of polyunsaturated fatty acid, omega-3, is mostly found in seafood and is the main component of the infamous “fish oil”. It hasn’t increased very much at all and so most people have an abnormally high omega-6:omega-3 ratio compared to the past and to the environment of evolutionary adaptedness.

Omega-3 and omega-6 fatty acids are important for cell membrane fluidity, especially in the brain where they affect neurotransmitter receptors and other neural functions. If there are the wrong amounts of them, this would very plausibly derange various cognitive functions.

So let’s look at Joseph Hibbeln’s paper Seafood Consumption and Homicide Mortality.

The Guardian describes it like so: “Hibbeln and his colleagues have mapped the growth in consumption of omega-6 fatty acids from seed oils in 38 countries since the 1960s against the rise in murder rates over the same period. In all cases there is an unnerving match. As omega-6 goes up, so do homicides in a linear progression. Industrial societies where omega-3 consumption has remained high and omega-6 low because people eat fish, such as Japan, have low rates of murder and depression.”

From Stephen Guyenet’s excellent post Vegetable Oil and Homicide:

I know, I know, it’s a nice pretty line, but where are the randomized controlled trials?

To which one answers: “in dozens of different countries around the world”. One of the most famous is Gesch et al 2002, which gave dietary supplements including fish oil or placebo to 231 prisoners and found a 25% drop in prison violence (p = 0.03) using intention to treat and 35% (p = .001) using completers. A replication study on 231 Dutch prisoners found almost exactly the same results. Another study of 468 schoolchildren also showed exactly the same results. And…actually, I’m just going to quote from Anatomy of Violence: The Biological Roots of Crime, a book I just found on Google and have suddenly conceived a burning desire to own:

In Australia, six weeks of omega-3 supplementaion reduced externalizing behavior problems in juveniles with bipolar disorder. In Italy, normal adults taking omega-3 for five weeks showed a significant reduction in aggression compared to controls. In Japan, a randomized controlled trial found that ADHD children with oppositional definat disorder showed a 36% reduction in their oppositional behavior after fifteen weeks of omega-3. In Thailand, a randomized double-blind trial of the omega-3 fatty acid DHA resulted in a significant reduction in aggression in adult university workers. In the United States, women with borderline personality disorder randomized into supplementation of the fatty acid EPA for two months showed a significant reduction in aggression. Another American study, this time a four-month randomized double-blind placebo-controlled trial of fatty acid supplementation in fifty children, showed a significant 42.7% reduction in conduct-disorder problems.

We have been burned by omega-3 before. Every couple of weeks someone makes an exciting claim about it, and a few weeks later it is shown to be false or overblown. A big government review of the research on mental health basically dismisses everything done thus far as insufficient to draw meaningful conclusions. But I am hopeful.

I will add one more chemical, one of my favorites. Lithium. Many studies (1, 2, 3 find strong (that last one is p = .00003) links between lithium levels in the water supply and an endpoint crime or suicide. Lithium is a known neuroprotective agent, is probably at least calming, and may be otherwise good for the brain.

I am not certain of this, but I have heard from a few sources that modern water treatment/purification removes most minerals, which would suggest we are getting much less lithium than people in the old days who got their water from a well or whatever.

So we are likely getting more lead, more omega-6 (and relatively less omega-3), and less lithium than people in 1850. If there has been an increase in crime and other undesirable/impulsive behaviors, I think these biological insults are at least as worthy of examination as political changes that have occurred during that time.

But while we’re figuring that out, can someone explain to me how polygenic inheritance works?

We have really strong evidence that intelligence is highly heritable – maybe 50% to 80%. But genome-wide association studies show very low contributions from any particular SNP:

The study found that the genetic markers with the strongest effects on educational attainment could each only explain two one-hundredths of a percentage point (0.02 percent). To put that figure into perspective, it is known from earlier research that the SNP with the largest effect on human height accounts for about 0.40 percent of the variation.

Combining the two million examined SNPs, the SSGAC researchers were able to explain about 2 percent of the variation in educational attainment across individuals, and anticipate that this figure will rise as larger samples become available.

Here’s my question. Things determined by a larger number of independent randomly varying processes should tend to vary less. Suppose at Casino A, you flip a coin and if it comes up heads they give you $5000 and if it comes up tails they give you nothing. But at Casino B, you flip 5000 coins, and get $1 for each coin that comes up heads and nothing for each coin that comes up tails.

Both games have the same minimum and maximum winnings ($0 and $5000), and both have the same average ($2500). But the variance will be very different. The winnings at Casino A will vary a lot; half the people will walk out with $5000 and the other half will walk out broke. The winnings at Casino B will vary surprisingly little: if I understand binomial distributions correctly, well under 1% of gamblers will walk out with less than $2400 or greater than $2600. Pretty much everyone goes home with something like $2500.

The more independent loci determine human intelligence, the less variation in human intelligence we expect to see relative to the total amount it is possible to vary. If the most important SNP explains 0.02%, then there are at least 5000 genes involved, which means, as in the example above, that less than 1% of people should differ more than 2% of total possible variability from the average.

But actually, people differ in intelligence a lot, and a lot of that difference seems to have a genetic component. This implies either that the total possible genetic variability in intelligence is huge – that the right genes could give you an IQ of 2500 or so, or that variability in intelligence isn’t simple and additive and random the way I’m modeling it here – or that I’m doing the math wrong, always a distinct possibility.

The easiest way to get out of this, other than accepting I am terrible at math and should be kept away from it, is to assume that lots of different genes for good intelligence are correlated. Maybe one population had reason to evolve high intelligence with lots of smart SNPs, and a second population didn’t. Then it would make complete sense that all the genes involved would co-vary. Unfortunately, there seems to be significant IQ variation within the same family, let alone within the same population group, so that fails pretty hard as an explanation.

Another possibility is to accept the whole mutational load idea – which allows for high correlations in goodness or badness of the entire genome. Unfortunately, this is the other idea in genetics which has been confusing me terribly over the past few months.

This has no trouble explaining correlations, but it does have trouble explaining why things aren’t more correlated. We should find the same people being very smart and very tall and very athletic and very healthy. I don’t doubt there are some correlations between these traits, but they don’t seem nearly as high as one might expect.

And the paternal age effect keeps being brought in to explain this, but I don’t get that one either. Suppose I have a kid at 60. My sperm and my DNA have had 60 years to accumulate deleterious mutations, so there’s more chance my kid will have low IQ or psychiatric disease or whatever. Fine. But suppose while I’m having a kid at 60, my twin brother has had a kid at age 20, and his kid had a kid at age 20, and his kid had a kid at age 20, so that his first great-grandchild is being born exactly the same time my first child is. Both my kid and his great-grandkid have had 60 years worth of cell dividings to accumulate mutations. Why should their risks of autism be any different just because his kid had those 60 years divided among three different people?

(does less frequent division of spermatogonia before puberty cause them to accumulate fewer mutations during that time? If so, shouldn’t three generations of people who have kids at 33 still accumulate 80% as many mutations as two generations of people who have kids at 50?)

I’ve heard evolution’s ability to eliminate people with bad genes used as an explanation here, but I don’t quite get it. For one thing, it seems unlikely that evolution can produce beneficial mutations at the same rate people accumulate deleterious mutations (10 per generation or so). And if we imagine two lineages of gradually deteriorating intelligence going on for 1000 years, the Lions That Selectively Eat Low-IQ People will have just as much opportunity to cull the members of the one that reproduces quickly as the one that reproduces slowly. And, if that were the explanation we should fail to see a paternal age effect in the absence of such lions (or be dysgenic as hell), but the effect has been demonstrated in our own society, which is relatively free of lions and of almost everything else that kills people before they can reproduce.

I know other people have blogs where they explain things and readers bask in their wisdom, but having a blog where I say how confused I am about stuff and readers explain it to me has always worked for me before and I have faith it will continue to do so.