Digit Ratios and Mutational Load

“Mutational load” is the idea that organisms contain some number of deleterious mutations. Some mutations will kill you outright, like the one for Tay-Sachs disease; some mutations greatly reduce your fitness but aren’t immediately lethal, like the inability to sweat; and some mutations are potentially problematic but mostly just kind of annoying, like colorblindness.

Random mutations happen all the time as a result of genetic transcription. The obviously bad ones tend to get weeded out of the population pretty quickly, but the ones with only a mild effect on fitness can stick around for a pretty long time. Under harshly Malthusian conditions where organisms compete for limited resources and danger and disease lurk at every turn, deleterious mutations will tend to get weeded out pretty quickly, but increase the food and decrease the danger/diseases, and a far larger % of your population will reproduce, including people who would previously have died.

One of the areas where mutational load seems to play a significant role is in IQ. I commented on a study n the subject back in “Is Genius Fragile?” While obviously a great variety of things go into determining one’s IQ, like whether you were in a good mood when you took the test and if your parents dropped you on your head as an infant, this particular study found that the major difference between extremely-high-IQ kids and normal-to-low-IQ people was that the normal-to-low people had a higher frequency of rare, slightly deleterious mutations. The lower the IQ, the more of these mutations.

Each mutation obviously has only a small effect–you could have several and still come out pretty smart. But to be one of the super smart kids, you had to basically be one of the lucky folks who escaped almost all of them.

IQ is interesting in another way: it is more variable in men than women. People make a big deal out of the greater preponderance of men than women at the very high end of the IQ distribution (especially math ability;) this is, we are frequently told, due to the pernicious evil effects of the patriarchy’s black-magic mind-control rays convincing women that they are bad at math. Strangely, however, we are never told that the opposite effect–the fact that the ranks of the intellectually retarded are also disproportionately male–is also due to the magical effects of the patriarchy.

BTW, if you think it is a problem that the evil patriarchy is preventing girls from getting math PhDs, but have no problem with boys being over-represented among the retarded, you are a horrible person.

No, it’s not the patriarchy. It’s the Y chromosome.

You see, because random unpleasant shit happens, like snake bites and random mutations, nature has built us with a fair amount of redundancy. If something happens to one of your eyes, you’ve still got the other. If something happens to one of your hands, you’ve got an extra. Etc. This is true on the genetic level, too, which is why you can survive even with small, fitness-reducing mutations.

But men have slightly less genetic redundancy than women, because they have an X and Y chromosome instead of two Xes. If a woman has a wonky mutation on one of her Xs, the other X may have a mutation that makes up for it. If a man has a wonky mutation on his X, his Y chromosome may have nothing to counteract it (and likewise, if there’s a wonky one on his Y, his X may have nothing to counteract it.)

Some mutations are good, some are bad, and some are neutral. Height is fairly neutral. The average man is taller than the average woman, but the spread from tallest men to shortest men is bigger than the spread from tallest women to shortest women. All women tend to cluster closer to the female average than men; there are both more “short men” and “tall men” than “short women” and “tall women.”

Likewise with IQ; there are both more male geniuses and retarded than female geniuses and retarded, most likely as a result of men having lower genetic redundancy to counteract the effects of mutational load.

On to digit ratios!

SlateStarCodex recently posted the results of the SSC/Less Wrong survey, which included digit ratios.

(To measure your digit ratios:

1. Place your right hand firmly on the plate of a photocopier or scanner with fingers straight. Close cover of place a sheet of paper over your hand to prevent glare from overhead lights. Ensure that the bottom crease and finger tip can be clearly seen in the photocopy.

2. Use a ruler or calipers to measure the distance from the middle of the bottom crease to the tip of the finger to the nearest hundredth of a centimeter.

3. Once you have the measures for both your ring and index finger, then divide the length of your index finger by the length of your ring finger. The result is 2D:4D (2nd digit divided by 4th digit).

If possible, please give three digits – for example, 0.915. Some people may have digit ratios slightly greater than 1, which is okay.)

Inspired, the husband and I decided to measure ours, too. Since we didn’t have a photocopier on hand, and were lazy, we just used a common tape measure. We measured both hands and checked each other’s work, but both of our hands came out identical.

I got a ratio of 0.971, he got 0.957.

(Note that the closer the ratio is to 1, the closer your fingers are to being the same length. The further the ratio is from one, the further apart your finger lengths are.)

Scott notes that the average male digit ratio in his survey was 0.972; the average female digit ratio was 0.975.

According to Wikipedia, a study of 136 males and 137 females at the University of Alberta found:[17]

  • Males: mean 0.947, standard deviation 0.029.
  • Females: mean 0.965, standard deviation 0.026.

People have taken to calling lower digit ratios (further from one) more “masculine,” and higher digit ratios (closer to one) more “feminine.” Which leads to the question of why all of these Rationalist math-nerds, whose community is definitely majority male and whose field is regarded as a stereotypically “Male” thing, should all have such overwhelmingly girly hands.

My first thought was that math nerds are effeminate. Which they are, for certain definitions of effeminate. But mathy women tend to be kind of masculine, which isn’t what this data shows. My second thought was that femininity/masculinity may be additive rather than subtractive–that is, having an extra unit of “masculinity” doesn’t necessarily mean someone must therefore lack a unit of “femininity” in a directly linear fashion. Some people could be very low in both femininity and masculinity, or high in both.

My third thought was that maybe measuring digit ratios is too complicated by measurement error and bias and random noise due to things like “how do your fingers crease?” and “did you actually use a copy machine?” A LOT of social science research doesn’t replicate at all.

My fourth thought was that a large difference between one’s finger lengths sounds a lot like physical asymmetry–which is caused (among other things) by mutational load.

Symmetry has long been recognized as one of the things people look for in a mate. Asymmetric faces (and bodies) are deemed less attractive than symmetric ones. Symmetry is a sign of good health, good lifetime nutrition, few parasites, and low mutational load. Asymmetry is a sign of things gone wrong.

Men display more of the effects of mutational load due to their Y chromosomes, so we’d expect to see a wider range of male digit ratios than female ones–which is indeed what the Alberta study found. Really dumb men probably have very different digit lengths, while really smart men trend toward even fingers. Women, because of their two X chromosomes, are probably just less likely to have really uneven fingers (just as they are less likely to be really dumb.)

The Slate Star Codex and Less Wrong cohorts, on the other end of the spectrum, are very smart people in whom we would expect to see lower mutational load.

The latest study I read on autism found that sufferers have a higher mutational load than the background population; while such an explanation is less fun than “autistics are secret math geniuses,” it is sensible. At any rate, if so, we should find a correlation between autism and divergent digit ratios, which the SSC/LW survey did. (Why autistics tend to be male should be immediately obvious.)

Likewise, if homosexuality is caused by some kind of genetic or parasitic agent, we would expect it to correlate with digit divergence. According to the Wikipedia, lesbians have more divergent digits than heterosexual women, but the jury is still out on gay men.

Interestingly, Wikipedia reports that the Han Chinese (who score very well on IQ tests,) have very even fingers, and that the Jamaicans (who do not do so well on IQ tests,) have very divergent ratios. (However, like much of this digit ratio research, I regard this as speculative.)

Of course, like height, there my also be an androgenic effect, such that men are supposed to (for whatever reasons) have slightly different digit ratios than women. After all, even the SSC/LW sample had more divergent ratios for the men than the women, even though the whole SSC/LW population probably has about equal mutational loads (having been pre-selected for high IQ, which = low mutational load.)

 

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update on the cathedral

YLS Clinical Students Represent Immigrant Women and Children Detained in Texas

Yale students debate renaming Calhoun College:

“Even if we could rename every single residential college after radical people of color, racism would still manifest itself on our campus every day.

“Because institutions such as Yale and the federal and state governments are inextricably implicated in the maintenance of racism in this country in ways that will take more to undo than hollow symbolic gestures.

“Don’t get me wrong, symbolism is important. But to fixate on a futile debate about whether or not to change the name of Calhoun College is to miss the more fundamental question of how to shift power relationships on our campus so that they are more racially just.”

The counter-article:

“Yale should do a better job of commemorating. I propose a yearly vigil on Dec. 20, the anniversary of Calhoun’s home state of South Carolina’s secession. We can read aloud the testimonies of the slaves Calhoun thought subhuman, and of the Union soldiers who fought to destroy his evil dream incarnate. In doing so, we will emphasize what Dean Holloway worries is too often ignored: “that African Americans have a humanity that ought to be respected.” It could be, I think, a solemn institutional repentance. Perhaps Calhoun’s victims would appreciate our piety on their behalf.”

I’m not sure what they’re disagreeing over.

From the Harvard Crimson: Delving Deep Inside Amy Schumer The significance of society’s inability to find women funny

That’s… significant?

“As Christopher Hitchens once said, and as Amy Schumer video commenters often echo, maybe women aren’t funny because they’ve never needed to be funny. I mean, it’s just evolution. Throughout the years, as dinosaurs evolved into chickens and as carrier pigeons evolved into iPhones, human males evolved a sense of humor because it got them laid more often. One knock-knock joke, and before he knows it, the lucky man is a father to a litter of funny boys and unfunny girls. Or something like that. Science!”

Wow, I think I have missed the ev psych theories on humor. But I don’t really have much of a sense of humor, so maybe I just haven’t been reading the correct things.

“Sorry to burst your bubble, but while humor is a lot of things, it’s a lot more than just a flirting device used by men to woo women. …

“No, humor is far more powerful than that. Humor—particularly satire—is a tool of social commentary and criticism. It’s a way for people to hold up a mirror in front of society’s face and point out all the pockmarks.

“Women, of all people, know that society is deeply flawed. When we routinely get paid less than our male colleagues, and when the length of our skirts determines whether or not we deserve to live—well, how could we not turn to humor to shine a light on society’s failings?”

Criticizing society is more powerful than evolution?

Sorry, hon. But evolution wins. Every match. Every time.

Also–skirt length determines whether or not we deserve to live? What the hell has happened to Harvard? Did it get taken over by the Taliban sometime last year and no one told me?

Harvard Law would like to note that it practically started the gay marriage bandwagon: The Road to Marriage Equality

“In an essay titled “Recognition, Rights, Regulation, Normalisation: Rhetorics of Justification in the Same-Sex Marriage Debate,” Halley expressed concerns that although limiting marriage to heterosexual couples indeed deprecated the relationships of gay couples who wished to marry, the fight for equality had too readily adopted language emphasizing the normative value of traditional coupling. Instead, Halley argued, the movement should question widespread assumptions about marriage and monogamy, leaving the door open for a broader range of non-traditional relationships.”

Luce Foundation Awards $400k to Harvard Law for the development of SHARIAsource

“SHARIAsource is a new initiative of Harvard Law School’s Islamic Legal Studies Program and Harvard’s Berkman Center for Internet & Society that will provide an online portal of resources and analysis on Islamic law, in cooperation with scholars of Islamic law and policy in the United States and around the world.

“SHARIAsource aims to be the go-to site for researchers, journalists, and policymakers, as well as generally interested readers seeking to grasp the basics and the complexities of Islamic law—a frequently recurring topic in news and policy circles. The portal will accomplish this goal by collecting primary sources (court cases, legislation, and fatwas) about Islamic law, and offering scholarly analysis and policy papers about them. The analysis will come from recognized experts in Islamic law and related fields in the United States and abroad.”

Actually, that sounds kind of useful. I once tried to do a project on Gypsy law, but got bogged down when I realized that law is really boring. Also, I couldn’t figure out how to find any Gypsies to talk to in real life in order to figure out if “Gypsy law” actually has any relevance to their lives.

Oh, and from Penn, which I guess is technically still in the IVY League, but really shouldn’t be with shit like this: I Sometimes Don’t Want to Be White Either

Hey, there should be a comma before “either.”

“There was a time in my 20s when everything I learned about the history of racism made me hate myself, my Whiteness, my ancestors… and my descendants. I remember deciding that I couldn’t have biological children because I didn’t want to propagate my privilege biologically. …

“Maybe it felt good to distance [Dolezal] from the overwhelming oppressiveness of Whiteness — her own and that of her country and of her ancestors. But the lesson for me is remembering how deep the pain is, the pain of realizing I’m White, and that I and my ancestors are responsible for the incredible racialized mess we find ourselves in today. The pain of facing that honestly is blinding. It’s not worse than being on the receiving end of that oppression.

“Ali Michael, Ph.D., is the Director of P-12 Consulting and Professional Development at the Center for the Study of Race Equity in Education at the University of Pennsylvania. She is also the author of Raising Race Questions: Whiteness and Inquiry in Education and co-editor of Everyday White People Confront Racial and Social Injustice. For readers interested in how White people can work towards racial justice — and still be White — or how a White person could have a positive racial identity without being a White supremacist, please pick up one of these books!”

Penn wins the WTF of the month award, despite that article about about Ruth Bader Ginsburg being a “Pop culture icon.” WTF.

In other news, Bruce Charleston reflects on, The destruction of the ‘basic instincts’, common sense and human nature – reflections on the mutational meltdown of Man

“We currently believe that general intelligence has declined by approximately two standard deviations (which is approximately 30 IQ points) since 1800 – that is, over about 8 generations. …

“Michael and I immediately recognized that the rate of change in intelligence that we were observing was too fast to be accounted for my natural selection favouring lower intelligence; although this does have a significant role.

“We soon began to recognize that the primary mechanism was likely to be mutation accumulation due to the decline in child mortality rates from more than half to about one percent – child mortality having, through human history, served as the main (but not only) selective ‘sieve’ to remove the spontaneous fitness-reducing mutations which occur with every generation.”

It’s a great post, IMO. I’ve been talking about the effects of the end of high infant mortality for a while (in conversation, not so much here, since this is a new blog and all.) I think the potential for unforseen effects is pretty high.

“In a sense, the reduction of intelligence may be one of the lesser concerns about this world of what looks increasingly like a mutational meltdown. Because mutations will also damage what might be termed the ‘basic instincts’ of the population or species.

“In particular, mutation accumulation will be expected to affect social and sexual instincts of the kind we used to call ‘common sense’ and ‘human nature’.”

To be fair, I am not so keen on endless population growth, myself. I think curbing growth is a sensible reaction to overpopulation, rather than something to be concerned about it. (Though obviously one does not want to get overwhelmed by people who don’t curb their growth.)