DARC matters

DARC (Duffy antigen receptor for chemokines) is a receptor expressed on red cells, key in the infection of those cells by vivax malaria. A version of the gene that eliminates expression of this receptor on red cells (and prevents vivax infection) has reached very high frequency (up to 99%) in sub-Saharan Africa. A new article in PLOS Genetics concludes that this was driven by some kind of strong selection, but a long time ago ( ~40,000 years). They estimate that the Duffy-negative mutation conferred a selective advantage of about 4.3%, leading to effective fixation in about 8,000 years. Not everywhere in Africa – didn’t happen in the Bushmen, Naturally they suspect that the selection was driven by vivax malaria , but they’re a bit mystified because today vivax is usually mild ( at last when compared with falciparum malaria). Vivax is often found in places where it can’t be transmitted year-round (because of winter) : it waits in the liver [hypnozooites] and reappears later, sometimes much later. I’ve heard of cases where it reemerged as much as 40 years later. Which means that it can’t afford to be too severe – it has to let the host survive.

However, in the tropics, it could get away with being more virulent, and perhaps it did, in the past.

An advantage of 4.3% is a lot, as selective advantages go, easily enough to drive a gene frequency from a tenth of a percent to 99% in a few thousand years. In much the same way, a behavioral tendency (heritable of course) that led men to have sexual intercourse with women other than their primary mate, when practical, could become very common even if it only resulted in a few percent extra surviving children per generation, say 2.2 instead of 2.1 . Compound interest. A behavior wouldn’t have to yield 100 extra children in order to become common (although producing an extra 100 would certainly have that effect!). In the same way, a heritable behavioral tendency that reduced the average number of offspring by a few percent would also become rare over a few thousand years.

What fraction of the practitioners in various human sciences understand this wee bit of population/quantitative genetics? Very few, I think.

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Ramble On

I’m raising money for another podcast with James Miller. I did one with him last year and had fun. Here’s the link. You can also send money via paypal, or bitcoins to 1Jv4cu1wETM5Xs9unjKbDbCrRF2mrjWXr5.

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Topics

I will probably be doing another podcast with James Miller soon. Suggestions are welcome. I’m considering reviewing more dreadful yet influential books and/or articles: readers have already suggested some, such as Jonathan Marks’ new book, and that article about twin studies in Slate. I would, I think, include books that are seriously wrong but not utter dreck. The candidates should include books that are not brand-new – I could diss The Republic, for example.
Name a book.

I will run gofundme or similar appeals for these efforts: I gotsta get paid.

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Old T-Rex

I’ve just finished Testosterone Rex, by Cordelia Fine. In this book, she argues against the existence of innate psychological differences between the sexes. She does not want her readers to believe that men and women have different natures – apparently because such differences, or belief in their existence, would prevent social equality of the sexes. Personally, I think the more important question is whether it’s true. But I would say that, wouldn’t I?

Rather than talk much about differences between the sexes, which would do her case no good at all, she talks about testosterone’s role in creating such differences. Testosterone is a strawman theory, here. Sex differences might be caused, in part or in whole, by biological factors other than testosterone: would disproving an incorrect testosterone-based theory make the differences go away? On the other hand, it might confuse people enough to reduce or eliminate belief in such differences. People are fairly easy to confuse.

Sex differences can be pretty big. Men are about 8% taller, but they have 90% greater upper body strength (about three standard deviations) and 65% greater lower body strength. They run faster, jump higher. Teenage boys routinely beat professional female athletes, as when the Newcastle Jets U-15 team recently defeated Australia’s national women’s soccer team 7-0.

There are psychological differences as well. Boys prefer rough-and-tumble play, girls prefer ‘intimate theatrical play’. Boys and girls have different toy preferences: boys like trucks, while girls prefer dolls. Interestingly, we see similar sex differences in play in other young primates, such as vervet and rhesus monkeys. Young chimpettes are known to carry a stick around, sticks that seem to be stand-ins for future babies – like dolls. Since other primates that are not exposed to anything resembling human socialization [they can’t talk] show similar play preference patterns, socialization is unlikely to be the driver of those patterns in humans, no matter how much Fine would like that to be the case.

Girls with congenital adrenal hyperplasia are exposed to high levels of androgens before birth: their play styles are more like those of boys, and they (like boys) are better at spatial rotation tests than other girls. Fine suggests that CAH girls are socialized differently [due to their medical condition] , and that this may account for their boy-like play preferences. The female offspring of rhesus monkeys treated with testosterone during pregnancy also show male-shifted play preferences, such as rough-and-tumble play. Similar effects are seen in rats. Socialization is powerful !

Men are far more violent than women, far more likely to commit murder [and suicide], in every society. Obviously, if we see it everywhere and everywhen, the cause must be … climate change.!

Men take more risks, especially after puberty. Fine attempts to talk this away, as she often does. Her argumentative approach sometimes has a certain mad charm, as when she mentions her baby son rolling across the room to a power drill, juggling knives, and trying to plunge a running hair dryer into the cake mix. I guess that no truly educated person could believe in anything so obvious, so… She also steps up to ” No true Scotsman “. She defines what must be the only correct definition of a risk-prone personality – someone that tends to embrace every possible risk – and if those correlations aren’t perfect, how could there be such a thing as a risk-prone person? She reminds me of Donald Rumsfeld, trying to define away the insurgency in Iraq by explaining that real guerrillas must have a unified doctrine and central command, which would have been a surprise to the raggedy-assed Spaniards fighting Napoleon, the men that gave us the word.

But crypts don’t lie. Teenage boys are twice as likely to die in accidents: you don’t see girls climbing down into the bear pit on a dare. To be fair, you don’t see boys do it twice. Young men are more likely to get killed making nitrogen tri-iodide, climbing Half Dome, or stealing copper from power lines. They can do it in a car, they can do it in a bar.

Almost all men are sexually interested in women, and the overwhelming majority of women are sexually attracted to men. I’ve heard that there are parallels in the animal kingdom. When you think about it, it makes a twisted kind of sense. Isn’t that a psychological difference?

Moderate differences in the average value of a trait can drive big differences out in the tails of the distribution. Men are only four or five inches taller than women, but all the tallest human beings are male. Men have a moderate edge in spatiovisual processing, but are overwhelming dominant – 100-1 – in the uppermost reaches of mathematics and science. Not just due to visuospatial differences, but that’s part of it. This also shows up in pool, which is not very dependent upon strength, but where the top men are much better players than the top women. Men’s advantage in spatiovisual skills likely plays a part in this. Jeanette Lee, when she was the top women player, said that there were ‘dozens of male players who could wax me.’ And, probably, even more that would have liked to.

Sexual differences are driven by selection favoring changes in one sex that lead to increased reproduction. This must explain men’s strength advantage, a product of competition with other males. Selection is the ultimate cause of psychological differences between the sexes, as well.

Generally, sexual selection is strongest in the sex with the greater reproductive variance. Usually, that means males – some have many offspring while others have few or none. Female reproduction varies less. Fine discusses a series of experiments by Angus Bateman [published in 1948] that led to claims of higher reproductive variance in male fruit flies. There were problems in those experiments – mistakes, technical problems and limitations. Some of the mutations used to trace paternal identity interfered with fitness and thus buggered the statistics. We wouldn’t have to use such a sloppy procedure today, but hey, it was 1948 – they didn’t even have the human chromosome count right. Yet similar studies have been done more recently on many other species – without those problems – and Bateman’s principle, that females are the limiting factor of parental investment, is generally true. Male reproductive variance is generally higher. So how does criticism of errors in a pioneering study refute a now-proven idea? That would be like claiming that Otto Lilienthal’s glider crash, where he died saying “sacrifices must be paid for” [which makes no sense at all] proves that Man will never fly. Fine’s fruit fly chapter is completely pointless. This lawyerly rhetorical technique, criticizing an early experiment in order to snipe at a well-established contemporary theory, was also used by S.J. Gould in The Mismeasure of Man, when he argued that Samuel Morton had skewed his measurements of skulls to fit his preconceptions. Which was untrue – but it wouldn’t have mattered a rat’s ass if Morton had screwed up, because the art has advanced very far since Morton’s time. Today we use MRI and CAT scanners to image skulls to millimetric precision.

Fine takes a stab at showing that there’s isn’t much point [in terms of extra evolutionary fitness] in men getting extra mates. She comes up with an unphysical and absurd example – mentioning how unlikely it would be for 100 one-night stands to generate an extra 100 babies. That’s totally irrelevant: all it shows is that she’s innumerate. Here’s the practical example: suppose some dude has a wife and a girlfriend next door. Suppose he has intercourse 50 times with each of them over a year – both are probably going to have a kid, while with just the wife , he would have had one. 2 > 1. Am I getting too abstract here? By the way, if sexual selection doesn’t really happen, what could explain men’s huge strength advantage? Eating Wheaties?

Fine seems to think that only producing a horde of extra kids could have any evolutionary significance – but she is wrong. One more kid is a big deal, fitness-wise. On average, over most of the human past, people only managed to raise two children to adulthood. In real life there are always other factors to consider, of course. Does he have enough resources to feed one more child? Is his girlfriend married, and will her husband be duped into raising someone else’s kid? Or will her husband get wise and clobber our protagonist?

Fine is inspired here by some work by Dorothy Einon, who attempted to show that a famous case, where Sultan Moulay Ismail (“the Bloodthirsty”) is said to have fathered 888 children, couldn’t possibly have happened. Einon was wrong: careful simulations show that it was possible, although Ismail did show real dedication. Fine manages to misunderstand Einon’s mistakes.

If you make a math model whose results that completely contradict common knowledge – if it predicts that the Saudi royal family does not exist, or that Miles Park Romney didn’t father 30 children – you would be well advised to recheck it. Just sayin’.

Fine goes on to criticize the ‘man-the-promiscuous-horny-hunter/woman-the-choosy-chaste-gatherer. It can’t be the case that men want sex more than women – why, if that were true, prostitution would exist. Ba-dum-bump. Among foragers, are men really the hunters, almost always? Of course they are: men have much greater upper body strength. Spears and arrows don’t launch themselves.

it is possible to argue against a too-simple version of that narrative. For example, in populations of European descent – the ones we’ve looked at – the rate of false paternity is low, around 1-2%, and has been for centuries. It is not the case that many women have children by alphas and trick betas into paying the bills.

Another approach would be looking at brains, trying to identify sex differences (or the lack of them) in brain structure. If men’s and women’s brains were indistinguishable, surely men and women be couldn’t be psychologically different. But that notion is a bit treacherous, since it assumes that we can detect all functionally relevant differences in the brain. We can’t – certainly not in living subjects, but not even in studies after death. How do you detect memories? Can we see the differences in the brains of border collies that make them want to herd sheep? Not yet. Fine discusses some work by Daphna Joel, a behavioral neuroscientist at Tel Aviv University. Joel thinks that there really aren’t differences between male and female brains. Oddly enough, other people, like Larry Cahill, can reliably identify a brain’s sex: no single currently measured feature is definitive (other than presence of a Y-chromosome) , but statistical approaches exist that can make that distinction almost perfectly. Women’s brains are smaller (even after adjusting for body weight), connectivity patterns are different, white/grey matter percentages differ, gene expression patterns in the brain are different, etc., etc. Daphna Joel is a bad source: she sees what she wants to see, and disregards the rest. Psychology seems to have a bad case of that, which is why we’re hearing about the “replication crisis”. Michael Inzslicht, a dealer in stereotype threat and ego depletion [and unicorns] , said ā€ As I said, Iā€™m in a dark place. I feel like the ground is moving from underneath me and I no longer know what is real and what is not.ā€

The incidence of mental illness is not the same in the two sexes: dyslexia and autism are much more common in males, depression more common in females. Sex differences in brain structure ( could be differences in gross anatomy or down at the molecular level) must be responsible for these differences in disease incidence.

In talking about the effects of testosterone, Fine mention a kind of cichlid fish where dominance influences gonadal events – causation ( in part) goes from behavior to hormones, instead of hormones to behavior. Interesting. But is there evidence of a similar pattern in humans? No. Are humans so evolutionarily close to fish – in particular, cichlid fish – that any pattern we see in cichlids is an immediate heads-up, something that might be happening in humans? Christ no. Then what’s the God-damn point? If we’re talking logic and inference, there is none: Fine seems to think that random unconnected facts are just fine for confusing her audience, and of course she’s right about that. Or, more charitably and probably more accurately, they’re good at confusing her. Makes me miss ye olde-fashioned steel-making, pistol-packing, Cheka-loving Commies: one of them could write an entire book explaining how humans are really vernalized naked mole rats while still sounding intelligent.

If, in this book, Fine had at some point conducted a sharp analysis and found the hidden causal pattern in a web of data, or had a sound mathematical model that answered the key question, or even casually tossed off a few accurate thoughts about the central limit theorem or Simpson’s paradox, I’d have to think that she was a bad person – dishonest. I see no sign of that.

At the end of her book, Fine says that we’re all for sex equality. I can think of at least a billion exceptions to that statement – but let me say this: I’m for what works. Listening to Cordelia Fine is not going to make things work better.

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Situational Joke

An anthropologist was telling me about a legend – that once upon a time, there was a successful chimp-human hybrid. Back in the 1920s, at the Yerkes National Primate Center at Emory University. This might sound impossible, since the chromosomes don’t match, while the two species have been diverging for six million years or more. But then horses and donkeys don’t have the same number of chromosomes, yet mules exist. And some crazy Saudis have managed (after many tries) to produce a couple of hybrids between llamas and camels, which split about 11 million years ago.

So I’m telling you there’s a chance.

More important, I found out that the anthropologist in question had never heard a particularly relevant joke, the one about the Irishman and the gorilla. Seems that a zoo in Chicago had a rare albino gorilla, the last of is subspecies. A lady gorilla. So they decided to breed it with a human: they put an add in the Trib:”Man to breed with rare gorilla, ten thousand dollars.” Thee next day Paddy shows up and talks to them. “I’ll do it, but with three conditions. I don’t have to kiss the gorilla on the lips, the children will be raised in the Church, and you give me a week to come up with the ten thousand dollars.”

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I will read and review Cordelia Fine’s Testosterone Rex

But only if somebody pays me enough money.

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Never Mind

A bit ago I talked about a paper making the case for male-heavy gene flow when the Yamnaya founded the Battle Axe [Corded Ware] culture. Looks as if it was mistaken.

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