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What does heritability reveal about genetic and environmental influences on a trait?

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Diagram of a DNA double helix showing its twisted ladder structure, with a close-up of the sugar-phosphate backbone, paired nitrogenous bases (adenine, thymine, cytosine, guanine), and labeled nucleotides and hydrogen bonds. — human genome The human genome is made up of approximately three billion base pairs of deoxyribonucleic acid (DNA). The bases of DNA are adenine (A), thymine (T), guanine (G), and cytosine (C).

In the context of genetics, heritability is a statistical estimate representing the proportion of observable (phenotypic) variation within a specific population that is attributable to individual genetic differences. It is expressed as a ratio ranging from 0 to 1, where a value of 1 indicates that all variation is due to genetic differences, and 0 indicates that all variation results from environmental factors.1

It is important to clarify that heritability does not measure the extent to which an individual’s traits are determined by genes versus the environment, nor does it indicate how sensitive a trait is to environmental change. A trait can have high heritability yet still be significantly altered by environmental interventions, such as dietary changes for certain metabolic disorders. Furthermore, heritability estimates are specific to the population studied and cannot be used to explain differences between different populations.1

Ultimately, heritability serves as a tool to partition phenotypic variation into genetic and environmental components, helping researchers understand the relative contributions of nature and nurture to complex human traits and behavior.12