Fifty years of twin studies


Jason Collins


May 28, 2015

If you’re familiar with the literature, this is unsurprising. A meta-analysis in Nature Genetics of 2,748 twin study publications points to the strong role of genetics and the weak role of family influence (a major component of “shared environment”) in shaping human traits. The abstract:

Despite a century of research on complex traits in humans, the relative importance and specific nature of the influences of genes and environment on human traits remain controversial. We report a meta-analysis of twin correlations and reported variance components for 17,804 traits from 2,748 publications including 14,558,903 partly dependent twin pairs, virtually all published twin studies of complex traits. Estimates of heritability cluster strongly within functional domains, and across all traits the reported heritability is 49%. For a majority (69%) of traits, the observed twin correlations are consistent with a simple and parsimonious model where twin resemblance is solely due to additive genetic variation. The data are inconsistent with substantial influences from shared environment or non-additive genetic variation. This study provides the most comprehensive analysis of the causes of individual differences in human traits thus far and will guide future gene-mapping efforts. All the results can be visualized using the MaTCH webtool.

Also of interest, most of the resemblance between twins is due to additive genetic variation. This is a positive sign for plans to identify the causal variants behind complex traits. It’s just a matter of getting those sample sizes up in genome-wide association studies.

Amusingly, in one case this study has been flagged as a tie between nature and nurture. But the “nurture” we are talking about here isn’t reading to your kids.