Genetics and Health

I Like Your Genes, Friend

by Hsien Hsien Lei, PhD on July 28th, 2005

Could we be even more similar than we thought? A new study of twins shows that spouses and best friends may be almost as similar to us genetically as our own brothers and sisters. (Medical News Today, July 27, 2005) Sounds a little too incestuous to me.

Using a 130-item questionnaire that measured social background, personality, and attitudes, researchers found that identical twins (who have identical genetic make-up) tended to have spouses and best friends who were more alike. Whether they based their preferences on physical appearance or mutual likes and dislikes, the twins were attracted to the same kinds of people.

The breakdown of factors contributing to the twins’ selection of spouses and friends were:

• 34% due to genes
• 12% due to shared environment
• 54% due to non-shared, unique environment

The genetic factors in this equation could be explained by evolutionary psychology - social preferences are partially dictated by genetic similarity.

“From arrays of possible alternatives, people seek those compatible with their genotypes,” J. Philippe Rushton and Trudy Ann Bons of the University of Western Ontario wrote. “People prefer their own kind — extraverts favor extraverts; traditionalists, traditionalists.”

“If you like, become friends with, come to the aid of, and mate with those people who are genetically most similar to yourself, you are simply trying to ensure that your own segment of the gene pool will be safely maintained and eventually transmitted to future generations,” the authors wrote.

Looking at the numbers, though, it’s obvious that environment influences the choice of friends and spouses much more than genes. The people who surround us are the only ones we can choose from to build our support system. We live in certain cities or countries because of work, family, or other obligations and usually, genes have nothing to do with it.

Clearly, Chinese people who remain in China will have more opportunity to choose spouses and friends from a pool of people who are more alike than not. On the other hand, perhaps the increasing number of inter-racial relationships in multi-cultural communities reflects the fact that we are more genetically similar than some would have us believe.

There are plenty of contradictions to this gene theory of social affinities. For example, my Asian-American friends who grew up in predominantly white neighborhoods prefer white friends and partners because that’s what they’re comfortable with. I live in Vietnam where I don’t speak the local language so I have only English-speaking friends regardless of their race. The increasing number of inter-racial marriages and relationships also reflects the extent to which a person’s living environment resembles a melting pot of cultures.

“We found that more than half of the variance in this study was due to unique environmental effects such as being in the right place at the right time.” Rushton added, “Similarity is only one of many factors in choosing a partner.”

That’s what I remind my single friends who are hoping to find the right one. And when I have trouble meeting new people after a move, I try to increase the number of places I go and the number of people I meet. Serendipity is the name of the friend game.

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POSTED IN: General Genetics and Health