No Evidence for Social Genetic Effects or Genetic Similarity Among Friends Beyond that Due to Population Stratification: A Reappraisal of Domingue et al (2018)

No Evidence for Social Genetic Effects or Genetic Similarity Among Friends Beyond that Due to Population Stratification: A Reappraisal of Domingue et al (2018). Loic Yengo et al. Behavior Genetics, January 2020, Volume 50, Issue 1, pp 67–71. https://link.springer.com/article/10.1007/s10519-019-09979-2

Abstract: Using data from 5500 adolescents from the National Longitudinal Study of Adolescent to Adult Health, Domingue et al. (Proc Natl Acad Sci 25:256., 2018) claimed to show that friends are genetically more similar to one another than randomly selected peers, beyond the confounding effects of population stratification by ancestry. The authors also claimed to show ‘social-genetic’ effects, whereby individuals’ educational attainment (EA) is influenced by their friends’ genes. We argue that neither claim is justified by the data. Mathematically we show that (1) the genetic similarity reported between friends is far larger than theoretically possible if it was caused by phenotypic assortment as the authors claim; uncontrolled population stratification is a likely reason for the genetic similarity they observed, and (2) significant association between individuals’ EA and their friends’ polygenic scores for EA is a necessary consequence of EA similarity among friends, and does not provide evidence for social-genetic effects. Going forward, we urge caution in the analysis and interpretation of data at the intersection of human genetics and the social sciences.

Keywords: Genomic similarity Social-genetic effects Confound Kinship

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The availability of large samples of individuals with genomewide genetic data in combination with behavioural phenotypes and social outcomes has led to a resurgence in research
that addresses questions at the interface of genetics and the
social sciences. Some of that research is hypothesis driven,
while much of it is data-driven and hypothesis-generating.
The genetics and statistical analysis of human traits has a
solid underpinning theory in quantitative and population
genetics (Lynch and Walsh 1998; Walsh and Lynch 2018),
and rigorous benchmarking against these underpinnings is
essential—especially when novel or unexpected results in
human behaviour are reported. In this paper, we highlight
one example (and list others) where novel results and claims
are not justifed by the data presented and instead have alternative and more parsimonious explanations.
Using data from 5500 adolescents from the National Longitudinal Study of Adolescent to Adult Health, Domingue
et al. (2018) claimed to show that friends are genetically
more similar to one another than randomly selected peers,
beyond the confounding efects of population stratifcation
by ancestry. The authors also claimed to fnd evidence of
‘social-genetic’ efects, whereby individuals’ educational
attainment (EA) is infuenced by their friends’ genes. Here
we argue that neither claim is justifed by the data.