Individuals in a long-term spousal situation appear to become more like each other as the relationship continues over time. The reason that this phenomenon occurs is because people select a spouse that is like themselves genetically according to research conducted by Benjamin W. Domingue from the University of Colorado Boulder and colleagues. The research was presented in the May 19, 2014, edition of the journal Proceedings of the National Academy of Sciences.
The researchers set out to compare the effect of genetic similarity and the effect of educational similarity on spousal relationships. The scientists compared the genetic makeup of 825 non-Hispanic white heterosexual American spousal couples to the genetic makeup of couples selected at random. The results indicate that people in spousal relationships have a much higher congruence of single nucleotide polymorphisms in their genomes than couples randomly paired.
The researchers compared this effect called “genome-wide assortative mating” to the effect of education on mate selection that has been previously documented as a factor in spouse selection. Genetics trumps education by 66 percent. The fact that people of similar genetic makeup may become associated in an educational environment reduced the effect of genetics on spouse selection to 42 percent.
There may be an ancient evolutionary imperative involved in the selection of mates that are like oneself. Genetic makeup determines likes, dislikes, sensory acuteness, and sexual preference. The research indicates that genetics makes people select mates that have similar personalities and behaviors.
A possibility not covered in the study is the growing similarity in behavior between long-term couples may in part be caused by another genetic phenomenon. Jumping genes have been reported in numerous ancient and modern species. Genes are transferred between species by contact. The intimate contact between people in a spousal relationship may produce a transfer of genetic material that causes the people to become more like each other.