Heritability: What's the point? What is it not for? A human genetics perspective

Abstract

In this paper, we explain the concept of heritability and describe the different methods and the genotype-phenotype correspondences used to estimate heritability in the specific field of human genetics.Heritability studies are conducted on extremely diverse human traits: quantitative traits (physical, biological, but also cognitive and behavioral measurements) and binary traits (as is the case of most human diseases). Instead of variables such as education and socioeconomic status as covariates in genetic studies, they are now the direct object of genetic analysis.We make a review of the different assumptions underlying heritability estimates and dispute the validity of most of them. Moreover, and maybe more importantly, we show that they are very often misinterpreted. These erroneous interpretations lead to a vision of a genetic determinism of human traits. This vision is currently being widely disseminated not only by the mass media and the mainstream press, but also by the scientific press. We caution against the dangerous implication it has both medically and socially.Contrarily to the field of animal and plant genetics for which the polygenic model and the concept of heritability revolutionized selection methods, we explain why it does not provide answer in human genetics.

Improving accuracy and precision of heritability estimation in twin studies: Reassessing the measurement error assumption

“…Model fitting can be improved by incorporating auxiliary information, such as accommodating abnormalities like skewness, outliers, and truncation through more inclusive and adaptive distributions (e.g., log-normal, ex-Gaussian). Additionally, one could reconsider the chosen partitioning into three components of h 2 , c 2 , and e 2 in twin studies and other assumptions (Robette et al, 2022): the additivity of genetic effects, the absence of assortative mating, the nonexistence of genetic dominance or epistasis, the generalizability from twins to the rest of the population, equal environment impact between MZ and DZ twins, and the absence of gene-environment correlation or interaction.…”

“…As an indication of potential predictability, heritability is an important statistical concept in assessing individual differences. Defined as the proportion of trait variability that can be ascribed to genetics, heritability offers a unique perspective for quantitatively understanding the role of genetics in complex traits (Downes and Turkheimer, 2022; Robette et al, 2022). Twins provide a hypothetically well-controlled scenario where genetics, environment, and their interaction can be statistically separated and apportioned.…”

The Bell Curve at 30: A Closer Look at the Within- and Between-Group IQ Genetic Evidence

“…Critics, however, argue that heritability estimates in behavioral research depend on several questionable or unsupported theoretical assumptions (see Block, 1995;Burt & Simons, 2014;Gusev, 2023;Hirsch, 1997;Ho, 2013;Keller, 2010;Lerner, 2018;Lewontin, 1974;McGuire & Hirsch, 1977;Moore & Shenk, 2016;Taylor, 1980;Wahlsten & Gottlieb, 1997). In a 2022 article, Nicolas Robette, Emmanuelle Génin, and Françoise Clerget-Darpoux examined heritability assumptions and concluded, "None of the hypotheses inherent in heritability estimates are verified in humans" (Robette et al, 2022). One heritability assumption is that genetic and environmental factors are separate (additive) and do not interact.…”

Bridging the diversity gap: Analytical and study design considerations for improving the accuracy of trans-ancestry genetic prediction

“…Finally, we assumed PGSs were transferrable at the population level. However, even within an ancestry-matched group, PGS predictions can be affected by sample variables such as the age or the sex of individuals, 37 or even at fine-scale within a population. 38 Our simulations are conducted using the five 1000 Genomes populations, but considering subpopulations would probably be needed to perform a more comprehensive evaluation.…”