For various reasons of my own, I was doing some light reading on sex differentiation and H-Y antigens and I came upon a wiki article about fraternal birth order, which says:
“It is hypothesized that the fraternal birth order effect may be caused by increasing levels of antibodies produced by the mother to the HY antigen with each son. The HY antigen (histocompatibility Y-antigen) is found on the surface of the cells of male mammals. The presence of this foreign chemical when bearing a son could trigger the mother’s immune response, which may then lead to different brain development patterns in later male children.”
Which got my head going in all kinds of gyne-utopian scifi kinds of directions, because doesn’t it sound like the mother’s body is actively preventing too much macho in the world? The “different brain development patterns” being obliquely referred to is of course gender variance and/or homosexuality in males.
Dunno: it just sounds like Charles Wallace and his mitochondria, in a way, doesn’t it?