Lecture 4

Students often ask why we use h rather than h to refer to heritability. You can blame Sewall Wright for this, as he used h to denote the correlation between breeding and phenotypic values within an individual. Recalling that the square of the correlation is the total fraction of variation accounted by a variable leads to the universal use of h. Indeed, whenever we speak of heritability, we always refer to h and never to h. To see that h is indeed the correlation between breeding and phenotypic values within an individual, note from the definition of a correlation that