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.
Latest posts by Sheldon Krimsky (see all)
- A Response to Boutwell and Anomaly’s “Why Sex (Really) Matters” - October 31, 2016