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People like genetically similar spouses

Harold Mandel's picture
A married couple

What attracts two lovers to each other has been an interesting topic of discussion since mankind first walked the planet. It often appears as if really happy spouses look like they are related. This is not surprising in view of the findings in new research that people are often attracted to someone else who has similar DNA.

It has been well established that people are generally more similar to their spouses in dealing with vital traits reports the Proceedings of the National Academy of Sciences of the United States of America (PNAS). For example it is often found that spouses have similar education levels.

Why spouses have genetic similarity

However, the actual genetic similarity between spouses has not been well understood. Researchers have found spouses are more in common genetically than two people chosen at random. However, this similarity appears to be at most about one-third of the magnitude of the educational similarity between spouses. It appears that when considering the marriage market social sorting processes are not completely dependent on genetic dynamics of sexual selection.

The development of an understanding of the social and biological mechanisms which lead to homogamy, or similar people getting married to each other, has been of deep interest to scientists for a long time. The researchers used a nationally representative sample of non-Hispanic white US adults along with information obtained from 1.7 million single-nucleotide polymorphisms. They compared genetic similarity among married couples to noncoupled pairs.

The researchers came up with evidence for genetic assortative mating from the population they studied. However, the strength of the association which they observed was markedly less than the strength of educational assortative mating found in the same sample. Also, genetic similarity was found to explain at most 10 percent of the assortative mating in regard to education levels.

People are likely to choose a spouse with similar DNA

The bottom line conclusion from this research is that people are more likely to choose a spouse who has similar DNA reports the University of Colorado at Boulder in a review of this research. Overall people have been found to be more genetically similar to their spouses than they are to people selected randomly from the population. It was already known by scientists that people generally marry someone who has similar characteristics, such as:

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1: Religion

2: Age

3: Race

4: Income

5: Body type

6: Education

This new study published by PNAS shows that people are also more likely to choose spouses who have similar DNA. Benjamin Domingue, the lead author of the paper and a research associate at CU-Boulder’s Institute of Behavioral Science, says it has been well known that people often get married to someone who is like them. However, there has been a question dealing with whether people mate at random in regard to genetics.

The researchers discovered there were fewer variations in the DNA between married people than between two randomly selected people. They used 1.7 million single-nucleotide polymorphisms in each person’s genome to estimate genetic similarity between individuals. The researchers made a comparison of the magnitude of the genetic similarity between married people to the magnitude of the more well studied phenomenon of people with similar educations getting married.

It was discovered that the preference for a genetically similar spouse, which is known as genetic assortative mating, is approximately a third of the strength of the phenomenon of educational assortative mating. Nevertheless, genetic assortative mating also has a real impact on choosing a spouse. It is interesting to observe that spouses are attracted to each other based on both genetic factors and other vital traits. This understanding may help us better predict which relationships have a better chance of success.