Tea at Trianon: A Gene for Divorce?

John Wilson Croker on Marie-Antoinette

"We have followed the history of Marie Antoinette with the greatest diligence and scrupulosity. We have lived in those times. We have talked with some of her friends and some of her enemies; we have read, certainly not all, but hundreds of the libels written against her; and we have, in short, examined her life with– if we may be allowed to say so of ourselves– something of the accuracy of contemporaries, the diligence of inquirers, and the impartiality of historians, all combined; and we feel it our duty to declare, in as a solemn a manner as literature admits of, our well-matured opinion that every reproach against the morals of the queen was a gross calumny– that she was, as we have said, one of the purest of human beings."

~from History of the Guillotine by John Wilson Croker, 1844

Edmund Burke on Marie-Antoinette

"It is now sixteen or seventeen years since I saw the queen of France, then dauphiness, at Versailles; and surely there never lighted on this orb, which she hardly seemed to touch, a more delightful vision. I saw her just above the horizon, decorating and cheering the elevated sphere she had just begun to move in, glittering like a morning star full of life and splendor and joy. Oh, what a revolution....Little did I dream that I should have lived to see such disasters fall upon her, in a nation of gallant men, in a nation of men of honor and of cavaliers! I thought ten thousand swords must have leaped from their scabbards, to avenge even a look which threatened her with insult. But the age of chivalry is gone; that of sophisters, economists, and calculators has succeeded...."

~Edmund Burke, October 1790

Thursday, November 9, 2017

A Gene for Divorce?

From Science of Relationships:

In a landmark study in this area from the early 1990s, researchers estimated the heritability of divorce to be about 50%.¹ What does a heritability estimate like this mean? Imagine a city or town where all of the people are either married or divorced. A heritability estimate of 50% means that the genetic differences between people in that city can explain half of why some people in that city stay married and why others get divorced. (What explains the other half of why some people get divorced? The environment!) Importantly, what a heritability estimate doesn’t mean is that half of the reason that Joe or Mary, individuals who live in our imaginary city, get divorced. In other words, a heritability estimate tells us that genetic factors play a role in general, but it does not explain why any one of us will experience divorce.

A heritability estimate also doesn’t tell us—by itself—whether we carry the specific genes or genetic variants that make us more likely to experience divorce. To find those genes, we would have to take a different approach. Right now, the most popular approach for gene identification is the genome-wide association study, which looks across the genome to see whether there are genotypic differences between people who do and do not have a trait or behavior of interest. For example, this analysis could determine if there are specific genetic variants associated with whether someone has straight or curly hair². No one has conducted a genome-wide association study of divorce (yet!), so it will be a while before we can ship off a saliva sample to 23andme (or any other direct-to-consumer genetic testing company) to find our risk of divorce.

A complicating factor in any such search for “divorce genes” is that divorce is what we call a “complex” outcome. In genetics, when we say that a trait or behavior is complex, we mean that there are multiple genes and genetic variants that influence that trait or behavior. Most of the things that psychologists and relationship researchers study—like how neurotic someone is, whether they have an alcohol or drug problem, or whether they are likely to get divorced—are complex traits. Contrast this with other types of outcomes that a single gene causes, such as Huntington’s disease or cystic fibrosis. The effect of each individual gene on a complex outcome like divorce is expected to be exceedingly small. This makes the search for “divorce genes” very challenging, like trying to find needles in a haystack. (Read more.)