-I am copying this straight from the textbook. Feel free to ask questions.. 

"Researcher Simon levay (1991) studied sections of the hypothalamus (A brain structure a link to emotion) taken from deceased heterosexual and homosexual people. As a gay man levay wanted to do "something connected with my gay identity". To avoid by seeing the results he did a blind study. Without knowing which donors were gay or straight after nine months of peering through his microscope at Hypothalamus cell cluster that seem to come in different sizes, he consulted the donor records. The cell cluster it was reliably larger in heterosexual men then in women and homosexual men. The question was when did the spring difference begin? Conception? During childhood or adolescence? Levay believes it more likely that brain anatomy influences sexual orientation. 

It goes on to say his hutch was confirmed, but I don't think it'll let me make a post that long