[Gayle]

My way of thinking about it is this -

Everything about us is controlled by our genes - they're what make us man/woman, blonde/brunette, short/tall etc.

If we accept that our genes - in various combinations can create someone who is extremely fair haired and someone who is extremely dark haired and every shade in between. If we accept that our genes - in various combinations can create someone with bright blue eyes and someone with dark brown eyes and every shade in between. Isn't it feasible that our genes can create (naturally) every shade of sexuality that there is?

Just my way of looking at it.