The paper addresses the long-standing controversy in evolutionary biology, medicine, and agriculture regarding the contribution of non-additive genetic variation to complex traits. Despite evidence suggesting that gene-gene interactions (epistasis) are important, empirical data across various traits and species indicate that most genetic variance is additive. The authors evaluate empirical studies of genetic variance components and find that additive variance typically accounts for over half, and often nearly 100%, of the total genetic variance. They present new theoretical results based on the distribution of allele frequencies under neutral and other population genetic models, showing that this is the case even if there are non-additive effects at the level of gene action. The study concludes that interactions at the gene level are unlikely to generate significant interaction at the variance level. The findings have implications for animal and plant breeding, gene mapping, and understanding the evolution and genetics of complex traits.The paper addresses the long-standing controversy in evolutionary biology, medicine, and agriculture regarding the contribution of non-additive genetic variation to complex traits. Despite evidence suggesting that gene-gene interactions (epistasis) are important, empirical data across various traits and species indicate that most genetic variance is additive. The authors evaluate empirical studies of genetic variance components and find that additive variance typically accounts for over half, and often nearly 100%, of the total genetic variance. They present new theoretical results based on the distribution of allele frequencies under neutral and other population genetic models, showing that this is the case even if there are non-additive effects at the level of gene action. The study concludes that interactions at the gene level are unlikely to generate significant interaction at the variance level. The findings have implications for animal and plant breeding, gene mapping, and understanding the evolution and genetics of complex traits.