The grandmothers effect, paternal or maternal matters (?)

I’ve discussed menopause as an adaptation and the grandmother effect before. I was also pleased to see the responses of Larry Moran’s readers when he presented his standard anti-adaptationist line of argument. I don’t want to retread familiar ground here, I’m not sure if menopause is an adaptation, but let’s assume so for the purposes of reviewing a new paper which has come out and offers a slight but fascinating twist on the grandmother hypothesis. Grandma plays favourites: X-chromosome relatedness and sex-specific childhood mortality: