The heritability of human disease: estimation, uses and abuses. Heritability can give initial clues as to the relative influences of “nature” (genetics) and “nurture” (environment) on complex traits, and it can give researchers a place to start teasing apart the factors that influence these traits. If heritability provides such limited information, why do researchers study it? Heritability is of particular interest in understanding traits that are very complex with many contributing factors. For example, hair color is a trait with high heritability, but it is very easy to change with dye. Heritability does not give any information about how easy or difficult it is to change a trait. For example, the language that is spoken tends to be shared in families, but it has no genetic contribution and so is not heritable. Traits can appear in families for many reasons in addition to genetics, such as similarities in lifestyle and environment. A trait is described as familial if it is shared by members of a family. Knowing the heritability of a trait does not provide information about which genes or environmental influences are involved, or how important they are in determining the trait. So, a heritability of 0.7 does not mean that a trait is 70% caused by genetic factors it means that 70% of the variability in the trait in a population is due to genetic differences among people. Heritability does not indicate what proportion of a trait is determined by genes and what proportion is determined by environment. Heritability can be difficult to understand, so there are many misconceptions about what it can and cannot tell us about a given trait: By comparing a trait in identical twins versus fraternal twins, researchers can calculate an estimate of its heritability. If a trait appears to be more similar in identical twins than in fraternal twins (when they were raised together in the same environment), genetic factors likely play an important role in determining that trait. Identical twins have almost no differences in their DNA, while fraternal twins share, on average, 50 percent of their DNA. Heritability has historically been estimated from studies of twins. Most complex traits in people, such as intelligence and multifactorial diseases, have a heritability somewhere in the middle, suggesting that their variability is due to a combination of genetic and environmental factors. Many disorders that are caused by variants (also known as mutations) in single genes, such as phenylketonuria (PKU), have high heritability. A heritability close to one indicates that almost all of the variability in a trait comes from genetic differences, with very little contribution from environmental factors. Characteristics such as religion, language spoken, and political preference have a heritability of zero because they are not under genetic control.
A heritability close to zero indicates that almost all of the variability in a trait among people is due to environmental factors, with very little influence from genetic differences. Heritability estimates range from zero to one. An estimate of the heritability of a trait is specific to one population in one environment, and it can change over time as circumstances change. In scientific terms, heritability is a statistical concept (represented as h²) that describes how much of the variation in a given trait can be attributed to genetic variation. Traits can include characteristics such as height, eye color, and intelligence, as well as disorders like schizophrenia and autism spectrum disorder.
Heritability is a measure of how well differences in people’s genes account for differences in their traits.