What Genetics Does And Doesn’t Tell Us

I was looking at various articles and blogs on genetics, race, and IQ. I was also looking at the comments. It got me thinking about the quality of the public debate.

Much of the analysis and discussion is high quality. There are many people involved who are intelligent and well-read. But there still is a lot of misunderstanding and confusion about the issues of heritability, genetic inheritance, and shared environment. Without understanding these issues, there is no way to tackle all the related issues of race, IQ, etc.

This is a topic that I’ve posted about before. In that post, I offered many different perspectives from both online sources and books. If you check out some of the info from that post, you’ll realize how many complex factors are involved in a trait getting passed on and how difficult it is to determine causal relationships, specifically determining genetic influence.

This post is a continuation of what I shared there. I feel compelled to return to the topic because of its importance.

I’ll keep this post simpler, though. I’m only going to offer four articles for consideration, all of them from the website Science 2.0. There is no particular reason I’m offering these articles from this website other than that they caught my attention as I was browsing the web. The authors explain the issues well and I want to use this opportunity to promote their explanations.

* * * *

What Is Heritability?
By Gerhard Adam

“Heritability” is a term used in many articles and through much of the scientific literature and invariably promotes the idea that it relates specifically to inherited traits. As a result, it is often assumed that the heritability of a particular trait relates to how much influence genetics has on the trait manifesting in an individual.

However, that isn’t what it means.

Heritability attempts to address the relationship between nature (genetics) and nurture (environment), so that as each changes, the variation between individuals within a population can be estimated based on these influences. In this context, “environment” simply represents everything external to the genome that could effect expression.

Therefore the first significant aspect of heritability that must be understood is that it tells us nothing about individuals. It is strictly an estimate of the variations that occur within populations. If heritability is applied to an individual it is a meaningless concept [since an individual cannot be said to vary with anything].

It also doesn’t tell us anything about the specific influence of genes on any particular trait, since that would be the result of inheritance. We also need to understand that a trait is something that is “selectable”. In other words, there exists a possibility that outcomes can vary in the expression of a particular trait. This follows from the Mendelian view of inheritance where genes are represented as two alleles [dominant and recessive], so that particular combinations would produce certain outcomes. Therefore if there is no variation in the alleles, then everyone has the same genes and heritability would be zero. Adaptations like having a heart or a stomach are not selectable (too many genes and interactions) and therefore tell us nothing about heritability. The primary difference is that adaptations represent the cumulative effect of changes over time that have gone to fixation in a population. As a result, there is no “selection” that would determine “heart or no heart”. Therefore we can consider that the heart is an adaptation, while the risk of heart disease is a trait.

[ . . . . ]

One difficulty that arises with heritability is that any considered trait must be demonstrably linked to genetic transmission. This can become problematic when heritability is used to evaluate behavioral traits where the genetic link may be tenuous. In an effort to measure heritability, there is often a reliance on twin studies under the assumption that variances between them must be accountable to environment since they are effectively genetically identical. However, as previously mentioned, this can result in difficult interpretations when the traits in question are purely behavioral. Until such time as behavioral traits can be explicitly linked to genes, any statement regarding heritability must be considered suspect.

Heritability: A Primer
By Josh Witten

RED FLAG: If someone says the heritability of X is Y, then they probably don’t know what they are talking about.

Folks in the know, know that there are two kinds of heritability, broad sense and narrow sense. Those knowledgeable folks in the know are aware that it is extremely important to clearly state which heritability one is using, as the interpretation of each is different.

[ . . . . ]

Broad sense heritability tells us what proportion of the phenotypic variation is due to the genotypes of the individuals of the population. It tells us nothing about how similar the phenotype of a child will be to its parent. For that, we need the narrow sense heritability.

[ . . . . ]

Human behavioral studies, such as on IQ, have it much more difficult. Environmental variance is very difficult to control experimentally. Statistical methods can be used to correct for the effects of known environmental variables, but one cannot be certain that all variables have been accounted for. Without knowledge of the environmental variance, one cannot determine the value of Cov(G,E). Underestimating environmental variance and assuming, without evidence, that Cov(G,E)=0, will lead to an overestimation of Var(G), Var(A), and both broad and narrow sense heritability.

In this context, it becomes impossible to interpret either broad sense or narrow sense heritability rigorously. It is even questionable whether these metrics have any validity at all.

For a more thorough examination of the issue of heritability of IQ along these lines, I recommend dusting off a Science paper from 1974 by Layzer entitled “Heritability analyses of IQ scores: science or numerology?”.

What Our Genes Tell Us About Race
By Michael White

The debate over race and intelligence has a long and tarnished history, although that doesn’t mean it’s not a legitimate scientific question to address. However, the debate has taken place almost entirely outside modern genetics, falling instead within the realm of psychology (such as work done by Arthur Jensen). Some writers would have you believe that science is converging on a consensus that the ‘IQ’ gap between various races is genetic (and that liberal conspirators are trying to cover it up). That claim is false. Researchers have not identified a single genetic variant with an impact on intelligence that falls along population lines. In fact several studies have recently tested variants in genes that appear to be involved in controlling brain size. No correlation with intelligence was found. Yes, genetics does play a significant role in intelligence, and many other traits. But there is simply no genetic evidence (and I mean real genetics, not psychology) for genetic differences in intelligence between human populations.

Why is this so? Other traits, like skin color, obviously fall along population lines. While skin color is obviously not a 100% reliable predictor, skin color is a major indicator of race. Irish, Kenyans, Pakistanis, and Chinese populations all have clearly different skin tones.

It turns out, not surprisingly, that the genetic variation for some (but not all) skin color genes does in fact follow population divisions, in contrast with most other genetic variation. This is most likely because skin color differences end up being relatively simple – a single variant of a gene (causing lighter skin, for example) can easily become common in a population through natural selection. The result is that you have different human populations with dramatic differences in skin color.

Other traits, however, are much more complex than skin color. Physical differences which are determined not by one, but many different genetic variants, are unlikely to split neatly by population. Intelligence is probably one of the most complex traits humans possess. It is almost certainly affected by variants in many different genes, and many of those genes have other important functions in the body. That means this: two different human populations could have easily developed differences in skin color between them, but differences in intelligence would have been extremely hard to develop, by chance or by natural selection.

Racial conflict has long been a part of human societies. Along with that conflict has come frequent speculation (most famously, but not exclusively among whites with European ancestry) that one race is inferior to another. Some have been worried that modern genetics would substantiate that belief, but our best genetic evidence to date shows those worries unfounded. Genetics does play a large role in the diversity we find among human beings. That diversity, in spite of some dramatic but superficial exceptions like skin color, is shared in common among all races.

Why Race Is Pseudo-Science
By Gerhard Adam

However, the premise is quite simple. If you can’t actually define it in scientific terms, then it cannot be science. Therefore any claims that derive from it are not science. Similarly, we cannot claim that “race” is valid by simply engaging in arm-waving arguments based on the fact that there are genetic differences between various population groups. “Race” must be fully quantifiable as specific heritable trait(s) that serves to identify the group in question.

[ . . . . ]

If the concept of race is to be scientific, then it would need to specifically identify the genetic criteria that is to be used for that differentiation. Merely claiming some external trait isn’t going to do it.

Such simplistic thinking is insufficient to raise the idea of “race” beyond anything except another convenient [or inconvenient as the case may be] cultural grouping.

[ . . . . ]

So, if we really want to pursue the topic of “race” or designating subspecies of humans, then lets do so on a scientific basis, and not some arbitrary socio-cultural designation. If “race” is going to be based on genetics, then it should be intuitively obvious that people will have their “racial” classification changed based solely on their personal family history. As a result, the designation of any particular “race” could actually change from generation to generation. Therefore any claim at racial knowledge that is based on arbitrary external traits rather than the specific genetic traits, is, by definition, wrong 7.

Show me the genes.




11 thoughts on “What Genetics Does And Doesn’t Tell Us

  1. At this point, we do not need to worry about genetics resulting in “proving” one race to be superior or inferior to another it would seem based on the articles.

    I think that we can safely say that the majority of racial attacks, particularly those coming from a non-academic background are motivated mostly by political ideology. That is not to say that genetics may not lead to other insights, but intelligence is not one of them.

    • First, there are many people out there interpreting data that they don’t fully understand. It is one of the most complex fields of science. It is one of those areas where the more you know the more you realize how little you know. This is why a little bit of knowledge can be dangerous.

      Second, there are many people outside the field of genetics doing research about genetics. In a lot of cases, they aren’t well-trained in research methodology and/or aren’t well-educated about genetics. A lot of the research about race comes from the fields of psychology and medicine. For example, there is a lot of genetics research done by doctors who have never been fully trained in research methodology and they produce low quality data.



      Genetics is still an amazingly young field of study. We’ve barely scratched the surface. It is likely much of what we think we know will be disproven or revised in our lifetime. But some people are unwilling to humbly accept so much uncertainty. Their ideological agendas won’t allow it.

      Research does indicate that there are interesting and insightful genetic differences between populations. Still, they don’t fit definitions of race. They are only general patterns based. There is no gene that every individual of one race has and all other races lack. It just does not exist. Even the genetics for dark skin involve separate genes that developed separately. All dark skinned people may look alike to many white people, but that says more about psychology than genetics.

      In particular, no gene has been found that explains IQ measurement differences between populations. There is lots of speculation and that is fine as far as it goes. I just don’t understand why people want to accept unproven hypotheses as facts. And I really don’t understand why the media is so sloppy about its reporting on science. Well-educated journalists should know better.

      • “. I just don’t understand why people want to accept unproven hypotheses as facts. ”

        Human nature.

        Remember, if someone wants to believe something, they will use any data to advance their arguments.

        If someone is fanatically opposed to something, they will not see the light, no matter how much objective evidence is provided.

        “And I really don’t understand why the media is so sloppy about its reporting on science. Well-educated journalists should know better.”

        This is not new. Note how the media has been covering global warming for example.

        Several issues:

        1. You’ve already answered your question in your comments. Journalists seldom are educated in the field of science, nor have they been taught the scientific method. Thinking scientifically alas, is restricted to a minority of the human race.

        2. Media is owned mostly by large mulinationals, none of whom have any particular interest in telling the truth

        3. Often owners of media have their own agenda to advance

        • Yeah, I know. Human nature. Yes, the issues with the media are not new. I fully understand all of your explanations. But it still doesn’t feel satisfactory. It just feels depressing.

          I can comprehend many things on an intellectual level. Yet they remain incomprehensible on some more basic level. Thinking about this gives me a sinking feeling. It makes me want to collapse on my couch, sigh, and take a nap with my cat.

  2. “I can comprehend many things on an intellectual level. Yet they remain incomprehensible on some more basic level. Thinking about this gives me a sinking feeling. It makes me want to collapse on my couch, sigh, and take a nap with my cat.”

    America’s divisions are far deeper than most are willing to admit. It’s not values or public policy that divides America. It’s basic philosophy.

    On one side, you have a group of people who believes that in the idea that policy and how we approach our lives should be based on facts, that we should apply the scientific method to well, everything.

    On the other you have a group of people who have a set of fixed beliefs and believes that anything that does not support those beliefs should be suppressed by all means possible.

    This is much deeper than political parties or anything like that. That’s the key problem.

    • I agree that there is a deeper divide than political parties. And this divide is dangerous. The fanatics who are against science and their cynical allies are more motivated than the average citizen and more politically influential than those who actively defend science.

  3. The really interesting question is, what are the implications of these findings?

    Winston Churchill once said:
    “The best argument against democracy is a five-minute conversation with the average voter.”

    But he also noted:
    “Many forms of Government have been tried and will be tried in this world of sin and woe. No one pretends that democracy is perfect or all-wise. Indeed, it has been said that democracy is the worst form of government except all those other forms that have been tried from time to time.”

    Of course, there are other issues. Whether a “true” democracy exists is an issue or if it has been too corrupted.

    • Well, “true” democracy… that is quite the discussion that could be had. I’m sure the ancient Athenians thought they had “true” democracy, but from our perspective ancient Athenian politics looks more like oligarchy and plutocracy. A ruling elite voting amongst themselves about how they should rule over the majority hardly captures the spirit of democracy. But the spirit of democracy is a nebulous creature.

      • Well … a true democracy would not be one where the top used propaganda or attempted to manipulate the media to force a public to act against its own interests.

        But at the same time, a true democracy does not compel people to become informed in many cases. If anything, people may become complacent … at which point true democracy would likely be lost.

        The price of democracy is a well informed citizenry. Something that most nations do not have.

        • Yeah, the price of democracy is a well informed citizenry.

          This relates to the idea of signalling in a free market. Hence the need for well informed participants in market transactions. And hence the inherent failure of capitalism when information inequalities form, leading to inequalities of power and wealth.

          Monopolization of information, manipulation of information, spreading of mis/disinformation, etc. The eternal clash between those who want to control and those who want freedom from being controlled. Information is the price and the prize, is the tool and the weapon.

          If there isn’t a free flow of information, there can’t be markets or citizens that are free. So, the free flow of information is the spirit of democracy, for it is representative and indicative of all other expressions of freedom.

          All of this relates back to the race issue. Racism, racialism, and race realism are just various defenses of inequality. It is a desire to naturalize inequality and so make it a doctrine beyond question.


          “And yet the underlying theme of racial science remains the same. It is a way of explaining social inequality as natural, and hence as inescapable. Racial theories, as Enlightenment philosophe Condorcet put it, make ‘nature herself an accomplice in the crime of political inequality’. The rich are rich, African nations are poverty stricken, Iraq is beset by violence, not because of power relations or social policies or sectarian divisions but because of natural inclinations.”

  4. http://quillette.com/2015/12/01/why-parenting-may-not-matter-and-why-most-social-science-research-is-probably-wrong/#comment-1072

    “One has to be very careful regarding the specific traits measured by twin studies before making sweeping generalizations and one cannot equate heritability with genes. As many lay folk are wont to do. The heritability for say, having five digits, is close to zero. This doesn’t mean that the trait isn’t due to genes, it means quite the opposite. Five digits are highly conserved, genetically. Because they matter. Most traits that are under strong selection have very low heritability scores. So when you see find scores of say .5 or more, that suggests that selection for that specific trait is fairly weak, or that genetic variation may be maintained by frequency dependent selection. The higher the score, the more genetic variation there is. So most traits that are alleged/touted as having a a strong genetic basis from these studies, in reality just means there are more genetic alternatives floating around in the population – because a single genetic solution has not been unilaterally favored & fixed by natural selection. I’ve not read the works that I saw mentioned here, but if they’ve made this common comprehension error, the conclusions echoed here as the title suggests – have things backassward regarding what matters.”


    “Currently, probably mostly for practical reasons, BG largely ignores the peer group culture, allowing it to systematically inflate heritability estimates in twin studies (secondary to not controlling for its effects). I suspect this is what largely accounts for the missing heritability problem in behavioral genetics”

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