I have been heterosexual for almost as long as I have had a conscious memory of myself. I remember having many boy suitors in first grade (I still remember their names), and liking it immensely, even though I did not reciprocate. I had my first crush on a boy with whom I shared a desk in our classroom in third grade. It was reciprocated. I developed (puberty - menses, breasts and all the rest of that) very late, the latest girl in my grade level despite being several months older than median age because I was born in Nov and my parents sent me to school late. So I can tell that sexual orientation in my case has absolutely nothing to do whatsoever with hormones. It is something much more fundamental and ingrained than that. When I was in high school, having developed by then a personal philosophy of relationships that postulated that being sexually possessive is not cool, I was extremely surprised when my mom told me that in preschool I was possessive with a boy - I pushed another girl saying that that girl wanted to caress the boy in question and I wanted to be the only girl to caress that boy. I was so embarrassed and ashamed when she told me that story! At any rate, this is preschool level heterosexuality, and I have more stories at elementary school level which are my own stories from my own memory. So it does seem to have started early. How about you?