Table 1: The circumstances under which an X-linked gene coding for favoritism of granddaughters would persist in a population (based on Rice et al. [8] mathematical model).

When X-linked mutation helping granddaughters at expense of grandsons is expressed in:It would increase in frequency provided the expense to grandsons is no more than (values below) times the benefit to granddaughters

All grandparents (dominant expression)2
All grandparents (additive expression)1.5
Grandmothers only (dom or add expression)3
Paternal grandmothers only (dom or add expression)no limit