Tag Archives: genetic traits

Thalassophilia unmasked

There is no gene for thalassophilia—yet, anyway.

My satirical post last week about scientists finding a gene for love of the sea was intended to make a point about how we view genomics today—and a historical point about how we smugly congratulate ourselves on being so much more sophisticated than early human geneticists and eugenicists. Most people got that it was a spoof, but I thought it would be worthwhile to discuss some of the deeper issues at stake.

Charles Davenport was a real scientist, and the quotes from him are real. Davenport was a geneticist in the first half of the 20th century and the leader of the American Eugenics movement during the Progressive Era. He is often demonized as wrong-headed, misguided, and simple-minded. Indeed, he could be all of these things. Davenport really did believe there was a recessive, male-linked trait for the love of the sea. Thalassophilia has become a classic example of how eugenicists could ignore obvious environmental explanations in favor of the hereditary. When I told my 11-year-old daughter about Davenport’s thalassophilia, she immediately saw the fallacy: the sons of ship captains learn their love of the sea, they don’t inherit it.

My larger point is that simplistic analyses like Davenport’s can be masked by numbers and fancy technology.

For years, medical genetics involved the search for genes underlying genetic disease. Diseases that were caused by a defective gene, and not, say, by a germ or some other environmental factor. But that distinction has been erased. We used to think of genetic traits and non-genetic traits. Now, non-genetic traits are called “complex”—i.e., partly genetic and partly environmental. In other words, all diseases, and indeed all traits are understood as partially genetic.

There are sound reasons for thinking this way. I’m not arguing that those genes don’t exist. I don’t question the data—I’m happy to believe that there really is a genetic association with all of these traits. Indeed, I think it’s becoming possible to find a real, verifiable genetic basis for almost anything you like.

The advent of genome-wide association studies (GWAS) has made it vastly easier to examine traits with smaller and smaller genetic contributions. In essence, you can pick your trait, sample the DNA of a large group of people, and scan their genomes for bits of shared sequence.

As a consequence, we have the recent bloom of studies describing the genetic component of all sorts of “complex” traits, from religiosity to getting drunk and beating people up. We’re only limited by our imaginations, and by the kinds of traits we’re interested in today.

Thinking about these recent studies, it occurred to me that these traits were not fundamentally different from Davenport’s old favorite, thalassophilia. I bet, I said to myself, that if sailing were as culturally important today as it was in 1919, people would be doing GWAS to find the genetic basis of sea-lust. And I bet they’d find it.

Of course, there are big differences between human genetics in 2011 and human genetics in 1919. Davenport advocated sterilization laws and immigration laws to manage and shrink what he saw as the swelling populations of the “unfit.” That would be inconceivable today. I don’t think we’re returning to a “new eugenics” in any meaningful sense.

But cutting across the cultural differences are some continuities. One of them is the desire to believe there is a simple genetic explanation for our tastes and talents. That I think is a dangerous view. So on the one hand, I think we should be careful to evaluate 1920s science by the standards of the day, rather than by those of the 21st century. And on the other, we must not delude ourselves that modern science is completely objective. Mechanistic explanations are not proof against cultural bias.

My spoof was intended as a word of caution, a way to inject a note of skepticism about genetic explanations of human nature. C.M (“Call Me) Ishmael, the journal Genetic Determinism Today, MysticGene, the 4C (“for sea”) variant, the salt-stained polo shirts and the sailing widows—all that was pure balderdash. As the motto of this site goes, “Here lies truth”— in roughly equal measure.

So, keep your heads up, folks—and watch for the keyword “Satire” in the Categories section of this blog. Thanks for reading.