She's an awful writer who ignores decades of research into animal studies where prenatal testosterone was given to female embryos. Give a female embryo testosterone and you'll have an aggressive lesbian animal with male behaviour patterns and a pseudo penis.

She also brushes off or doesn't mention how attempts to raise boys with normal prenatal testosterone exposure as girls were abject failures.

There's a perfect natural experiment for this called the guevedoces. These boys have normal testosterone in the womb, they just don't convert it to dht so thier penises don't grow and they appear externally to have vaginas. Not even thier parents know they are male.

They grow up with typical male gender identity and usually get spotted long before their penises develop at puberty because of their play behaviour.

You see similar effects in boys with cloacal extrophy.

Fine just doesn't look at these kids.

I know radical feminists cling to all differences bare down to socialisation and you can't see brain sex, but most neurobiologists disagree. Of the two publishing who say it's not a thing, I could easily find a dozen looking at sexual differentiation.

You can see an adult brain change a bit during hrt in transexuals, and you see changes during puberty that vary by sex. It's one of the reasons all the research studying trans has to make sure they aren't on hormones.

You have to remember she's selling books, not doing science.