Question

A study was performed to estimate the heritability of human height. Heritability estimates were initially performed in children (average age 5 years old), and found to be 0.74. Heritability was estimated again in the same set of individuals when they were adults (average age 40 years old), and found to be 0.30. How can these results be explained?

Answer 1

heritability = genotypic variation / total phenotypic variation

heritibility = genotypic variation / ( genotypic variation + environmental variation)

(note: when interaction is absent, phenotypic variation = genotypic variation + environmental variation)

genotypic variaton remains constant throughout the life. It is irrespective of age. that is won't change with the change in age.

But environmental variation occurs with advancing age. in this case it is assumed that, environmental variation increased over time, which decreased the heritibility ratio. So their exists a relative change in the performance of the genotype in the given environment ( i.e, here, age group - upto 5 and in adulthood). so there is change in the heritibility.