Modeling assortative mating and genetic similarities between partners, siblings, and in-laws

Abstract

Assortative mating on heritable traits can have implications for the genetic resemblance between siblings and in-laws in succeeding generations. We studied polygenic scores and phenotypic data from pairs of partners (n = 26,681), siblings (n = 2,170), siblings-in-law (n = 3,905), and co-siblings-in-law (n = 1,763) in the Norwegian Mother, Father and Child Cohort Study. Using structural equation models, we estimated associations between measurement error-free latent genetic and phenotypic variables. We found evidence of genetic similarity between partners for educational attainment (rg = 0.37), height (rg = 0.13), and depression (rg = 0.08). Common genetic variants associated with educational attainment correlated between siblings above 0.50 (rg = 0.68) and between siblings-in-law (rg = 0.25) and co-siblings-in-law (rg = 0.09). Indirect assortment on secondary traits accounted for partner similarity in education and depression, but not in height. Comparisons between the genetic similarities of partners and siblings indicated that genetic variances were in intergenerational equilibrium. This study shows genetic similarities between extended family members and that assortative mating has taken place for several generations.

Correlations between human mating partners: a comprehensive meta-analysis of 22 traits and raw data analysis of 133 traits in the UK Biobank

“…This suggests that AM for EA is consistent with genetic homogamy, and that mates may be assorting on some trait that is more genetically than environmentally correlated with EA. Contrary to Robinson et al's (2017) 32 finding, Torvik et al (2022) 48 did not find evidence for genetic homogamy in educational attainment in a sample of partners, siblings, and in-laws in Norway. Instead, they found evidence that AM on EA was due to a mix of both social homogamy and phenotypic homogamy.…”

“…Contrary to Robinson et al’s (2017) 32 finding, Torvik et al . (2022) 48 did not find evidence for genetic homogamy in educational attainment in a sample of partners, siblings, and in-laws in Norway. Instead, they found evidence that AM on EA was due to a mix of both social homogamy and phenotypic homogamy.…”

Publicly Available Privacy-preserving Benchmarks for Polygenic Prediction

“…In fact, earlier experiments (data not shown) indicate that for certain other traits (Height and BMI) this effect is also present. This suggest the effect could be caused by assortative mating, since there is a significant body of evidence suggesting assortative mating effects for these effected traits [44, 24, 49, 37]. Also, we feel it is worth noting that this very discrepancy might be exploited as a measure of assortative mating.…”

Conventional twin studies overestimate the environmental differences between families relevant to educational attainment

“…26 However, a large Australian study found that spousal convergence played a negligible role in partner similarity for EA, 27 and recent molecular genetic studies have found strong evidence for phenotypic assortment on EA and/or associated traits. [28][29][30][31][32][33] A recent Norwegian study estimated the genetic correlation between spouses for EA at 0.37. 32 It also estimated the genetic correlation between siblings at 0.67 -a figure which suggests that CTD estimates of EA have been doubling the difference between MZ and DZ twin correlations to estimate heritability when tripling the difference might be more appropriate.…”

“…[28][29][30][31][32][33] A recent Norwegian study estimated the genetic correlation between spouses for EA at 0.37. 32 It also estimated the genetic correlation between siblings at 0.67 -a figure which suggests that CTD estimates of EA have been doubling the difference between MZ and DZ twin correlations to estimate heritability when tripling the difference might be more appropriate. Martin (1978) 34 developed a method to correct CTD ACE estimates for bias due to assortative mating when data on spousal correlations for parents is available.…”