Programme Leader of the Medical Research Council of the Human Reproductive Sciences Unit at the University of Edinburgh
Con to the question "Is Sexual Orientation Determined at Birth?"
"No-one has actually measured the levels of androgens in foetuses or the womb - you can imagine it is difficult to do - so this [the Nature article by Williams et al.] is all speculation. It may be informed speculation, but I think when we get on to a subject as touchy as sexual orientation we need to clearly define what is speculation and what is fact."