29 December 2014

Deconstructing “race science”

After I posted a quote from Ta Nehesi-Coates about The Bell Curve, a poster asked (paraphrased): OK, so that study is flawed, but how do we know that the various races are intellectually equal?

My answer is basically that “race” doesn’t correspond to any systematic genetic difference that might mean anything when compared to measured intelligence, assuming we could even define and measure intelligence. But I feel like that answer needs more unpacking and detail around it, so here goes.

Let me first say that I’m going to use the term “race science” to refer to all the purportedly scientific studies showing that white people are smarter than black people, Asian people are smarter than white people, and so on. The most popular recent example of “race science” is The Bell Curve, which still gets trotted out by people who ought to know better, but the theories go back centuries and I’m going to aim to explain why they’re all garbage.

So: The idea behind “race science” is that if we look at people of different races, we can measure differences in average intelligence for the different races — that some races tend to be smarter than others. Furthermore, “race science” holds that these apparent intelligence differences, measured using IQ tests or some similar tool, are because of racial genetics.

First of all, the scientific consensus is that this view is bullshit. As a specially convened task force of the American Psychological Association politely put it in response to the controversy over The Bell Curve:

It is sometimes suggested that the Black/White differential in psychometric intelligence is partly due to genetic differences (Jensen, 1972). There is not much direct evidence on this point, but what little there is fails to support the genetic hypothesis.

They then give a couple of examples of controlled studies prior to 1996 which showed no genetic link between skin color and intelligence.

That term “controlled studies” is key. It’s very hard to come up with a good controlled study on whether skin color and intelligence are linked — that is, a study where all the other possible factors are controlled for, and the populations whose IQ is measured only differ by race. And as the APA document notes, when people have managed to come up with such a study, the results haven’t supported “race science”.

But hey, let’s flog this dead horse some more, as people seem determined to try to revive it.

It’s common for people to further criticize “race science” based on the fact that IQ tests don’t really measure intelligence. There are many reasons why identifying IQ test scores with actual intelligence is problematic. I’d certainly recommend reading about those, and the Wikipedia article on The Bell Curve has a good summary. But I think that focusing on the weaknesses of IQ as a purported measure of intelligence is missing the point, as there are much bigger reasons why “race science” is bullshit.

Let’s start with the biggest single reason why “race science” is bullshit:

“Race” is bullshit.

Curiously, Penn and Teller never recorded that episode, but PBS has a nice list of 10 things everyone should know about race. The second one is that race has no genetic basis. That is, you can’t take the genome of a person and use that to assign them to a particular race. Race simply isn’t defined that way. Rather, the thing we call “race” is an arbitrary social construction. Not only does it not reflect the underlying genetics, it also varies depending where you are in the world. Your race is basically what the people around you decide it is by looking at your appearance and behavior, influenced somewhat by what you decide you want to identify as.

A person of Mexican descent who lives in England might be perceived as white. In Texas, they definitely won’t. When I moved to Texas I had to get used to the fact that a whole class of people I considered white, suddenly weren’t considered white by everyone else.

Ta Nehesi-Coates has talked to Professor Neil Risch about his paper Characterizing the admixed African ancestry of African Americans, which looked at the genetics of black African-Americans:

From cluster analysis, we found that all the African Americans are admixed in their African components of ancestry, with the majority contributions being from West and West-Central Africa, and only modest variation in these African-ancestry proportions among individuals. Furthermore, by principal components analysis, we found little evidence of genetic structure within the African component of ancestry in African Americans.

Quoting the background info from the paper:

For example, the largest study of African Americans to date, based on autosomal short tandem repeat (STR) markers, found an average of 14% European ancestry with a standard deviation of approximately 10%, and a range of near 0 to 65%

So just looking at African-Americans, i.e. those who live in America and have black skin and believe that their recent ancestors are from Africa, you still see a range of anywhere from 0% to 65% European genetic markers. So you can’t map race onto genetic markers in any straightforward way. Stand me next to a white American and a black American, and I might be genetically closer to the black American, even though my skin color is closer to the white American.

This isn’t some new revelation. UNESCO issued a position statement back in 1950 pointing out that race was not a biological fact, but an artificial social construct.

But hey, for the sake of argument, let’s pretend that race is just a matter of skin color, as coded for by genes. Let’s continue to pretend that IQ test scores measured intelligence. Is it true that skin color has some correlation with IQ test score?

Well, no. Again, as the APA document points out, when people have managed to find unusual populations that have differences in skin color alone, they’ve not found IQ test differences. And if you pause to think about it, why on earth would you expect them to?

Black skin is exactly the same as white skin, except that because of variation in a selection of genes, the amount of particular types of melanin in the skin is different. Eye color and hair color work the same way.

There are about 100 genes which code for some part of the melanin cycle. There’s one key mutation of one key gene which accounts for the largest part of the skin color difference between Africans and Europeans, but even that only accounts for around a third of the color variation. We’ve known for decades that there are actually many different ways skin can end up “black”:

The Negritos of the islands of Luzon and Mindanao in the Philippines, for instance, superficially resemble other dark-skinned groups in Africa and Australia. Yet their overall genetic affinities turn out to be far stronger to the lighter-skinned Asian peoples who surround them.

So if you measure IQ of “black” and “white” populations, you’re not even measuring populations that have anything genetically in common. The “black” group will include people who are genetically more “white” than many people in the “white” group. So “race science” is literally garbage data in, garbage answer out.

Squirrels_2287
Creative Commons License Robert Taylor via Compfight

But let’s ignore even that problem, and imagine we are studying genetically similar people of European descent, and genetically similar people of African descent — so we’re looking at just that one key gene mutation mentioned earlier. Let’s imagine our subjects all grew up in the same cultural environment, so we can ignore all the problems with the cultural biases of the IQ test. What about then — might we expect to measure a meaningful IQ difference?

Well, skin color is a matter of small variations in genes. However, the melanin in the brain which we know to be important is a different kind to the melanin in the skin, eyes and hair. While there is eumelanin (the skin color type) in the brain, we don’t have any evidence that it serves any purpose. (As an aside, this means that the theory that black people are innately superior because of their increased melanin levels — a kind of reverse “race science” — doesn’t hold up either.)

So asking whether black skin leads to a genetic predisposition to lower intelligence is really just like asking whether blonde women are naturally more stupid, or whether gingers are naturally weak and overweight. It’s like calling for scientific research on whether green eyes mean you’re better at math.

But in fact, the genetics of human hair color have been teased out quite precisely:

Further study showed that the region of human DNA that contained the single nucleotide change associated with blondness specifically affected the expression of KITLG only in hair follicles. […]

(Emphasis mine.)

“It’s clear that this hair color change is occurring through a regulatory mechanism that operates only in the hair. This isn’t something that also affects other traits, like intelligence or personality. The change that causes blond hair is, literally, only skin deep.”

In other words, melanin in the brain and melanin in the hair aren’t even affected by the same gene mutations. The mutation that changes hair melanin levels has literally zero effect on brain melanin. So there’s simply no plausible mechanism by which the blonde hair mutation would affect intelligence. There’s no reason to believe that skin color should be any different.

If you want further reading, PBS has links to articles. I’d also suggest reading about Theodore W. Allen’s book “The Invention of the White Race”, which sets out the history of how race — and in particular, the “white race” — was an invention of 17th Century American plantation owners, who used it to shore up slavery by creating a new division between poor white laborers and black slave laborers.

White Squirrel Looking Alert
Creative Commons License Adrian Wallett via Compfight

In summary: Race is an invented social construct that is used to distract the disenfranchised from class issues. It doesn’t correspond to genetics or to skin color. Hence studies showing that some races are genetically predisposed to higher intelligence are garbage. You can’t even get as far as discussing nature vs nurture, because you haven’t grouped by anything that corresponds to a feature of nature.

At this point you might be asking: OK, so if the differences in The Bell Curve aren’t attributable to race, or even to skin color, what causes them? The answer seems to be that we don’t yet know. There are a lot of possibilities. Ultimately, I suspect that the data are just too noisy to let us analyze them and get a clean answer. But science can tell us a few things that aren’t plausible explanations…

Hopefully soon we can move on to more serious questions, like whether gingers have souls, or whether all humans having souls is just liberal dogma.

© mathew 2017