Married couples with shared ancestry tend to have similar genes

Married couples tend to look alike for several reasons. One of them, new research shows, is the simple fact that married couples with common ancestry tend to share similar genes.

According to the study, published this week in the journal PLOS Genetics, the genetic similarities are enough to bias genome studies.

Researchers analyzed the genomes of three generations of Caucasian couples from the Framingham Heart Study, which began tracking the heart health of Framingham, Mass., residents in 1948. The analysis revealed significant selection bias among the 879 spousal pairs.

Study participants with Northern European, Southern European and Ashkenazi ancestry were likely to select a spouse with similar ancestry, though the selection bias diminished with each successive generation.

The analysis also showed the selection bias resulted in strong genetic similarities among couples. In other words, spouses with similar ancestry shared more genetic commonalities than couples without common ancestry.

Measuring biases created by "ancestral assortative mating" is important for genomic studies looking at disease heritability, researchers said in the study.