Comment by Southwards on Fraternal Birth Order Effect and the Maternal Immune Hypothesis · 2024-09-07T11:39:37.448Z · LW · GW

Interesting tidbit.

Evolutionary biologist William R. Rice critiqued the FBOE hypothesis shortly prior to the publication of this study. According to Rice, it wouldn't take long for a modifier to evolve to prevent the maternal immune response: 

"why would over 200 million years since the origin of mammals not be enough to evolve some modifiers preventing very costly neg- ative immune reaction of the female body to such a routine and unavoidable event as pregnancy with a male fetus (50% of all pregnancies)?"

Rice has a competing hypothesis which links male homosexuality to sexually antagonistic epimarks. Who knows if it pans out. I know epigenetic inheritance is quite controversial (although Rice told me the mechanism he implicates is less controversial than the blogs suggest). His hypothesis makes sense in that it provides a non-gentic mechanism controlling sensitivity to prenatal hormones: gay male fetuess are thought to fail to erase epimarks from their mothers, meaning their brains are buffered against the effects of masculinizing androgens.