On Detecting Good Genes

One of my pet peeves is the oft repeated claim that the basis for one’s affection for another person is rooted in a desire for their genes. Something traceable to our “Caveman” days.

An example of this claim I read recently was made by someone talking about the Wiener affair. She explained – feebly I thought – why women should not pick attractive husbands. Excusing women (and men) for how they are “wired” to pick a mate she said this (bold emphasis mine):

But who can blame her? She, like so many women — and men — pick a mate based on pretty predictable factors, dating back to caveman days when all we were trying to do was survive and keep our species going, according to physical anthropologist and Why Him? Why Her? author Helen Fisher, who has been studying human courtship for decades. We’re drawn to guys like Weiner because they have good genes we can pass on to our kids. The downside is that we take a huge risk on whether he’s going to be sexually faithful to us.

There’s so many problems with the claim it’s difficult to know where to begin my criticism. First of all, men and women are not drawn to each other based on an affection for genotype; if anything they are drawn to each other based on phenotype, i.e. broadly on the features and behaviors the other exhibits. It is not possible to know simply by assessing somebody’s phenotype whether they have good genes or bad genes. One reason is that for the vast majority of human phenotypes, even those we might want our children to inherit, we have no idea what genes are involved. Take intelligence for instance. Undoubtedly, there is a genetic basis that explains some variability in intellectual ability. Although we don’t know what that genetic basis is precisely, we do know that environment and learning play a huge role in outcome. So if your goal is to have smart children, then you are as likely, or maybe more likely, to get them if you raise them in a learning environment similar to the environment other smart people experienced in their formative years, than by trying to identify a mate with “good” genes. Again, for the simple reason that we don’t know what genes code for intelligence, even if one somehow could detect “good” genes.

For the record, I share the belief of many systems biologists who think intelligence, like other complex phenotypes, can not be explained by the activity of one or a few gene products.

Another basis for my criticism is that, even if you believe that phenotypes (traits) are directly encoded by the genes, you would still fail to detect the “infidelity” gene(s) in Weiner because he is deliberately keeping that behavior secret from potential mates. I’m certain his wife was unaware of those “bad genes” when she married him. Had she been able to detect the “infidelity gene” in Weiner, and wanted to save her son (or daughter) from inheriting this perfidy, presumably she would not have married Weiner. Just as a person who, assuming their primary concern was the quality of their children, would hesitate to marry another person if they knew that person had a bad gene that might recombine during meiosis with their own bad copy to cause a debilitating disease in their child.  This is the basis for certain Mendelian disorders in children, caused by inheriting a bad (recessive) gene from both parents, nether of whom is affected. The biggest reason many of these diseases are not prevented in children is not because we don’t know the bad gene(s) involved, sometimes we do, but precisely because, contrary to what the author of the article claimed, we can’t detect by observation if a person has “good” genes or “bad” genes.

I think the reason people continue to repeat this silliness – generally, that what we do as humans is explained by our genes and our desire to mate with someone with “good” genes – owes to their being duped by an increasing number of books and pop science articles related to evolutionary biology, many of which greatly oversimplify human biology in order to account for what we do or why we do it. These people don’t understand the actual science, or the corresponding limitations of our present knowledge.

UPDATE: In the event you are skeptical that any scientist would take the idea that there is a human gene for infidelity seriously: here you go.