Heritability – an explanation
Factors including genetics, environment and random chance all contribute to the variation between individuals in their observable characteristics. The heritability of a trait within a population is the proportion of observable differences in a trait between individuals within a population that is due to genetic differences. Because heritability is a proportion, its numerical value will range from 0.0 (genes do not contribute at all to phenotypic individual differences) to 1.0 (genes are the only reason for individual differences).
For instance, some horses in a population are faster than others; heritability attempts to identify how much genetics are playing a role in part of the population being faster and how much of that is environment or other factors. Heritability is measured by estimating the relative contributions of genetic and non-genetic differences to the total phenotypic variation in a population. Heritability measures the fraction of phenotype variability that can be attributed to genetic variation.