Research on heritability of IQ infers, from the similarity of IQ in closely related persons, the proportion of variance of IQ among individuals in a study population that is associated with genetic variation within that population. This provides a maximum estimate of genetic versus environmental influence for phenotypic variation in IQ in that population. "Heritability", in this sense, "refers to the genetic contribution to variance within a population and in a specific environment". In other words, heritability is a mathematical estimate that indicates how much of a trait’s variation can be attributed to genes. There has been significant controversy in the academic community about the heritability of IQ since research on the issue began in the late nineteenth century. Intelligence in the