The relationship between biology and sexual orientation is a subject of research. A simple and singular determinant for sexual orientation has not been conclusively demonstrated; various studies point to different, even conflicting positions, but scientists hypothesize that a combination of genetic, hormonal and social factors determine sexual orientation. Biological theories for explaining the causes of sexual orientation are more popular, and biological factors may involve a complex interplay of genetic factors and the early uterine environment. These factors, which may be related to the development of a heterosexual, homosexual, bisexual or asexual orientation, include genes, prenatal hormones, and brain structure. (Full article...)