As I was going to Saint Ives, I met a man with seven wives. Each wife had seven sacks, each sack had seven cats. Each cat had seven kits. Kits, cats, sacks, and wives, how many were going to Saint Ives?
To summarize: at least in males, exposure to abnormal levels and balances of hormones such as testosterone, androgen and estrogen in the womb can result in different brain development that is related to sexual orientation and identity. Particularly in males with certain xq28 chromosome variations.