Chances are, you’re going to marry someone a lot like you. Similar intelligence, similar height, similar body weight. A new study of tens of thousands of married couples suggests that this isn’t an accident. We don’t marry educated people because we happen to hang around with educated people, for example—we actively seek them out. And these preferences are shaping our genomes.
“This is a very exciting paper,” says Matthew Keller, a behavioral geneticist at the University of Colorado in Boulder who was not involved with the work. “Much ink has been spilled on why mates are correlated on so many traits.”
To conduct the study, Matthew Robinson, a postdoc in the lab of geneticist Peter Visscher at the University of Queensland in Brisbane, Australia, and colleagues turned to large databases that include information on human physical and genetic traits. They homed in on a person’s genetic markers for traits such as height and body mass index (BMI) to predict the height and BMI of their partner. If the underlying genetic traits suggested an individual was tall, for example, their partner should also be tall. Then the researchers compared the partner’s actual height against the predicted height.
Matthew Robinson在澳大利亚布里斯班昆士兰大学遗传学家Peter Visscher的实验室中做博士后工作,他和同事们将研究方向转向了大数据,这其中包括人类生理及遗传性状的信息。他们通过追踪个人的遗传标记特征,例如身高和身体质量指数(BMI),来对其伴侣的相关数据进行推测。如果被测对象的潜在基因特征是高个子,那么他的伴侣也应该是高个子。随后,研究人员将被测人员伴侣的实际身高和预测身高进行了对比。
When the scientists performed these calculations for more than 24,000 pairs of husbands and wives of European ancestry, they found a strong statistical correlation between people’s genetic markers for height and the actual height of their partner. They also found a statistically significant, but weaker, correlation between people’s genes for BMI and actual BMI in partners: People had actively chosen partners with similar genes to themselves, the team reports today in Nature Human Behaviour.
当科学家们对超过24000对欧洲血统的夫妻进行计算时,发现他们伴侣的预测身高和实际身高之间具有很强的相关性。同时,他们还发现伴侣的实际BMI和预测BMI之间也具有统计学意义,但是相关性较弱。研究团队在《Nature Human Behaviour》上表示,人们会主动选择跟自己有相似基因的伴侣。
This is evidence in humans of assortative mating, which is a form of sexual selection in which individuals with similar?traits?mate?with one another more frequently than would be expected under a random mating. It has been documented in nature, such as when more brightly colored eastern bluebirds mate with each other and when duller colored bluebirds pair up—or when big Japanese common toads mate, whereas small ones stick to themselves. Such assortative mating increases relatedness in families and can help their offspring survive better as long as the trait under selection (larger size, for example) continues to be beneficial—helping males acquire and fend off mates, for example.
The researchers also tested for assortative mating in other traits, such as years of education, in 7780 couples in a U.K. database. They looked for concordance among partners in genetic markers previously linked to years of education, and found a remarkably high correlation. This doesn’t mean that people choose mates based on actual years of education, but it likely implies that they select for similar interests, which are associated with level of education, Robinson says.
These findings suggest that mate choice “affects the genomic architecture of traits in humans,” Robinson reported in the paper. Assortative mating boosts the odds that a trait, such as height, will be passed to offspring. That has implications for genetic models that predict how likely it is that members of a family will inherit a trait, whether it’s a disease such as schizophrenia or a physical trait, such as height.
The next step, says Keller, is to use the new method to “understand why spouses are similar on many other, behavioral traits, such as IQ, political preference … and psychiatric disorders.” Robert Plomin, a behavioral geneticist at King’s College London, adds that new research suggests humans with autism, schizophrenia, and attention deficit hyperactivity disorder tend to marry each other, and that the new method can explore whether those choices, too, are rooted in DNA.
Robinson hopes to use his method to test more similarities in couples, including his own marriage. “Yes, we both have Ph.D.s and we’re both tall,” he says. “We fit the bill.”