Hormonally mediated inheritance of acquired characteristics in Mongolian gerbils.

The intrauterine position relative to members of the same or opposite sex that a rodent fetus occupies affects both its morphology and behaviour when adult. Female fetuses that mature between males are androgenized by testosterone crossing fetal membranes, and their phenotypes as adults differ significantly from those of sisters that received less intrauterine exposure to exogenous testosterone. We report here that adult female Mongolian gerbils that gestated between male fetuses produce litters containing a significantly greater proportion of sons than the litters produced by those that gestated between female fetuses. Consequently, daughters delivered by dams that gestated between male fetuses are more likely to have gestated between male fetuses and be androgenized in utero than are daughters of dams that gestated between female fetuses. Female gerbils thus tend to inherit the phenotype (either androgenized or not androgenized) of their respective mothers.