Women born with a rare condition that gives them a Y chromosome don't only look like women physically, they also have the same brain responses to visual sexual stimuli, a new study shows.
The condition is known as complete androgen insensitivity or CAIS.
Our findings clearly rule out a direct effect of the Y chromosome in producing masculine patterns of response, said Kim Wallen, an Emory University professor of psychology and behavioural neuroendocrinology .
It's further evidence that we need to revamp our thinking about what we mean by `man' and `woman'
The Y chromosome was identified as the sex-determining chromosome in 1905.
Females normally have an XX chromosome pair and males have an XY chromosome pair.
Women with CAIS are born with an XY chromosome pair.
Because of the Y chromosome, the women have testes that remain hidden within their groins but they lack neural receptors for androgens so they cannot respond to the androgens that their testes produce.
They can, however, respond to the oestrogens that their testes produce so they develop physically as women and undergo a feminizing puberty .
Since they do not have ovaries or a uterus and do not menstruate they cannot have children.
We didn't find any difference between the neural responses of women with CAIS and typical women, although they were both very different from those of the men in the study , Hamann said.