Heritability of IQ, Height and Obesity

Like… racial groups in America have different mean heights.

White men in America have a mean height of 5'10'’ with a standard deviation of 3 inches. Black men have about the same mean. Asian and Hispanic men have a mean height around 5'7'’.

So it seems quite possible for human traits to vary by one standard deviation. That’s the same order of magnitude that the race and IQ theorists talk about.

My article on IQ, Race and Racism actually already talked extensively about my view of heritability and IQ. I would ask you to re-read the sections “Heritability of IQ Score” and “Is Heritability a Sensible Concept?”.

Basically I don’t think a heritability measure tells us very much at all. It may mean genes matter a lot or it may mean that the environment is simply very homogenous. These measures seldom quantify the variation in the environment in any way.

I have seen example of studies where one has dealt with populations believed to be short for for genetic reasons. Yet when they moved to another country, it turned out that in fact here was primarily environmental reasons for their difference in height.

We can see significant differences between height between different white populations. Whites in America as well as different white populations in Europe. Over time there has been significant differences in height between these populations. Differences which has changed far more rapidly than evolution operates. E.g. the Dutch went from among the shortest to the tallest in Europe quite quickly.

White Americans used to be a head taller then white Europeans. But today white Americans will typically be shorter than Northern Europeans.

Not to mention obesity which has a high heritability score. Yet within just a few decades Americans went from being very similar to Europeans to being considerably more obese. Clearly there are significant environmental changes at play which are poorly captured by heritability measures.

E.g. because fast food culture spread almost universally across the US, a measure of heritability for obesity will not capture the environmental effects of a fast food culture.

If your theory is that human traits can’t differ, because “genetic differences are minor”, why doesn’t that theory also discounts the possibility of all phenotypic differences?

I don’t discount differences. I just think they are minor. As elaborated above, I don’t think you can e.g. attribute height and obesity to race, just because you may be able to measure such differences. E.g. if you measured obesity among different populations it would be easy to conclude that if you are Asian you are just bound to be really thin, because in most of Asia people are slim.

But you can just go to Hawaii and see how wrong that conclusion would be. Japanese people growing up on Hawaii with American culture have an entirely different build from Japanese people growing up in Japan. Yet heritability studies would suggest the build is almost all genetic, because the measures are done within fairly homogenous environment such as either Japan or Hawaii.

While it is plausible that Asians are shorter than whites and blacks for genetic reasons. I don’t think you can truly prove that without doing the following:

  1. Have a large number of Asian children who are born to e.g. white mothers. In vitro fertilization or something similar. Why? Because it seems to environment in the uterus may have a significant impact on how you grow later.
  2. These same Asian children are then raised as white kids. Eating the same kind of food. Why? Because a lot of Asians even when living in the West tend to have quite a different diet.

E.g. the Minestota transracial study mentioned in my first article shows this about IQ:

Child and Parent | IQ Score
White-White | 101.8
Black-White | 98.5
Black-Black | 89.4

It shows how an apparent differences in IQ between African-Americans and white Americans is largely gone when a black child is raised in a white family. It does not seem unreasonable to me that the few points remaining can be attributed to prevalence of institutionalized racism.

In other words whenever one starts to dig deeper, it almost always seem to me to show biology matters less than people assume.

In a very general sense, I’d like to say these arguments (race and IQ, race and crime) persist because the answers are not clear, not because the answers are obvious and the racists just aren’t listening.

I am not entirely onboard with this conclusion. Certainly there are people with a genuine interest. But a major part of the reason these discussions exists is because there is a right-wing political agenda to make it count. They want to prove racial differences to serve their political agenda.

And then there are the contrarians who don’t like that people want to shut down the discussion. I was certainly one of those in the past. I certainly became quite reactionary towards leftists who wanted to assert without any apparent proof that races did not exist or that differences don’t exist. Sadly I think such attitudes has hurt the cause more than it has helped. It causes many people similar to me to have almost went into a slippery slope into the alt-right.

I just hate shitty emotional arguments and are prone to take the opposite stance of those who make them. Today I am just more at ease with the reality that a lot of people with good intentions simply overstate their case. The fact that they overstate their case, does not make the fundamentals of it wrong.

Geek dad, living in Oslo, Norway with passion for UX, Julia programming, science, teaching, reading and writing.

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