A third limitation is that we may have overestimated the variance accounted for by common genetic variants. One reason is that population stratification can potentially inflate the variance accounted for by SNPs even after controlling for population structure (Browning and Browning 2011), though probably very little (Goddard et al. 2011). Another reason is that common genotyped SNPs that trace distant relatedness will to some extent reflect the relatedness at old causal mutations that have been co-inherited with the SNPs, so the effects of these rare variants may be partially captured. As such, our estimates are best considered as an upper limit of the additive variance that can be due to common genetic variants, but this only strengthens our conclusions regarding the small role they play in personality traits and the evolutionary implications of this.
