Genetics
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A Response to Boutwell and Anomaly’s “Why Sex (Really) Matters”

The essay by Anomaly and Boutwell begins by emphasizing the importance of sex and ends by asserting that sex and reproduction are done for different reasons and I would add increasingly by different methods. These statements are generally recognized as true. However their statements about heritability, the genetic basis of behavior, and IQ are regrettably ill-informed, exaggerated or trivialized and are not grounded in good or consensus science.

Let’s take heritability. It is a population measurement of a proportion, namely the measurement of a variation in a phenotype (physical characteristic or behavior) due to a genetic variation in a population. So if we have genetically identical plants (no genetic variation) and we find a variation in their heights, then the heritability is zero.

H2 =   Var (G)/Var (P).

The concept of heritability refers only to traits that differ among individuals. A trait that is exactly the same may be inherited, but it is not heritable. Also, heritability tells us nothing about individuals. Also, you cannot measure heritability without studying the environment. By changing the environment, you may change the measurement of heritability (a quotient of variance) for biological entities.

To say that “practically every psychological and physiological outcome is to some extent heritable” doesn’t say very much. It says nothing about whether an individual inherited a trait from their parents. Calculating one number for heritability in one environment may not hold up in another environment. And if there is no variation in the relevant alleles (plants have the same genes), heritability would be zero.

If the environment is identical for each biological entity in a population, the variance of the phenotype in the biological entity must be the result of genes alone. Thus the heritability would be 100 percent.

For humans there is no absolutely equal environment, even for twins. Yet the environment may play a lesser role than for non-twins. I say “may” because the “equal environment assumption” in twin studies is subject to debate. Twin studies have been a critical method for deriving numbers for heritability of phenotypes.

Broadly speaking, eugenics means healthy breeding or breeding healthy progeny. In centralized eugenics, the state dictates breeding programs. In decentralized eugenics individuals or communities play that role. Thus, in some orthodox Jewish communities, genetic testing is used to avoid certain marriages.

The authors are correct that individuals are gaining more choices over reproduction based on new knowledge of genetics and the right of women to have abortions. Also, new technologies can increase women’s chances of pregnancy through IVF treatments. Whether that is viewed as more control depends on whether you believe the prospective parents or the reproductive technologists have the control.

The challenge for society is where the moral boundary is or should be between selecting embryos by screening (a practice currently acceptable) and genetically engineering embryos or gametes. If we cross the germline barrier in human reproduction, we have to be prepared to do what is done when we create transgenic plants and animals. We discard the bad one. If a transgenic embryo is brought to term, are the parents or society obligated to protect its life no matter how disabled?

The authors state that “assuming genetic engineering emerges in the next century, the availability of cheap and accurate genetic information will become increasingly important.” It certain will in the area of forensics. But sequencing genes does not tell us much about illness. Even the DNA sequences for so-called monogenic traits cannot tell us the penetrance of the effects on a person. There are many other factors including epigenetic, the environment and other parts of the genome. It is far more than reading the code. It is how the system works.

As far as proposing intelligence exams for parents who want to have children, which sounds like Hitlerian eugenics and would violate reproductive autonomy, this can never be justified in a democratic society where having children is a basic right. Contraception is not a eugenics program unless it is targeted or mandated by the states to certain groups of individuals. Thus far all the claims made about genes and abnormal or aggressive behavior has not stood up to rigorous scientific evaluation, as was the case with XYY.

We are at a stage where genome-wide studies are producing results based on correlations that are not grounded in causal mechanisms. It is science by statistics such as “my genes will determine whether I go to the polls or not“.

 

Sheldon Krimsky is the Lenore Stern Professor of Humanities & Social Sciences and Adjunct Professor of Public Health & Community Medicine at Tufts University.

4 Comments

  1. Come on man, these are tired old arguments against heredity and behavioral genetics that are easily refuted. Perhaps one day we won’t hear them as much.

    To say that “practically every psychological and physiological outcome is to some extent heritable” doesn’t say very much. It says nothing about whether an individual inherited a trait from their parents. Calculating one number for heritability in one environment may not hold up in another environment.

    Tired misleading assumption #1 (well, first I’m addressing here). This is true in principle, but meaningless in practice. This is because there are few examples of this actually happening in humans. Heritability estimates replicate across the world. Few solid examples of “gene-environment interections” are known. Please stop touting this line.

    And about “whether an individual inherited a trait from their parents,” – I guess my idea of where the individual’s genes come from is flawed…

    For humans there is no absolutely equal environment, even for twins. Yet the environment may play a lesser role than for non-twins. I say “may” because the “equal environment assumption” in twin studies is subject to debate.

    Oh come on now. The equal environment assumption has been tested to death. It holds. Boutwell even co-authored a paper rigorously detailing such. Please drop it.

    The challenge for society is where the moral boundary is or should be between selecting embryos by screening (a practice currently acceptable) and genetically engineering embryos or gametes. If we cross the germline barrier in human reproduction, we have to be prepared to do what is done when we create transgenic plants and animals.

    Really? Well I thought from reading this piece that heredity wasn’t a thing. Why are you worried about it now, if it wouldn’t work?

    You know, farmers are in business, and have been for some time…

    If a transgenic embryo is brought to term, are the parents or society obligated to protect its life no matter how disabled?

    If a disabled human born from regular old conception is brought to term, are the parents or society obligated to protect its life no matter how disabled? I think we already have our answer.

    But sequencing genes does not tell us much about illness. Even the DNA sequences for so-called monogenic traits cannot tell us the penetrance of the effects on a person.

    Perhaps at our current state of knowledge, when few causal variants have been identified. That’s not going to stay that way forever.

    There are many other factors including epigenetic

    Horse bollocks, and you know it. If you don’t, you should.

    the environment

    Sure, strictly speaking. But as the heritability of most traits is in the 65-85% range, knowing the genomic configuration gives you a lot of predictivity.

    and other parts of the genome

    No kidding. Extra credit to anyone who can point out the silliness here.

    Thus far all the claims made about genes and abnormal or aggressive behavior has not stood up to rigorous scientific evaluation, as was the case with XYY.

    See above. Give it time.

    Besides, you’re confusing knowing that genes affect behavioral traits (which we know they do, considerably) and knowing which genes do so and how. Two completely separate matters.

    We are at a stage where genome-wide studies are producing results based on correlations that are not grounded in causal mechanisms. It is science by statistics such as “my genes will determine whether I go to the polls or not“.

    But they do, to a considerable extent.

    This is a horrible piece. Hopefully we’ll see fewer articles like this.

    See also my page:

    The Behavioral Genetics Page – The Unz Review

  2. Santoculto says

    ”By changing the environment, you may change the measurement of heritability (a quotient of variance) for biological entities.”

    Depend on robustness/universality of this traits. or not.

  3. Santoculto says

    I will repeat…

    – eliminate complete genetic maladies,

    – universalizing the potential to the free will via bio-engineered ratio-nality,

    – find a way to eliminate full mental disorders but don’t sacrifice ”creativity” (hyper-perceptiveness, the pre-condition to the punctual or generalized creative achievements),

    – remain human behavioral diversity, that is not morally incorrect.

  4. Pingback: Eugenics: Problem? - Bleeding Heart Libertarians

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