Research into the biological bases of homosexuality has continued unabated in the intervening decade in such diverse areas as endocrinology, genetics, neuroanatomy, family demography, or animal behavior.

In this work is covered this current strongest research lines on male and female sexual orientation.

Despite inconsistent results across studies, some support for the neurohormonal theory is garnered, but mostly in men. Genetic research using family and twin methodologies has produced consistent evidence that genes influence sexual orientation, but molecular research has not yet produced compelling evidence of specific genes. Anatomically there is evidence of some degree of cerebral sexual dimorphism, but it's not established yet the correlation to sexual orientation.

This studies indicate biologic factors have an important role on homosexuality, the degree and the way this factors act and interact with psychosocial determinants still being a clue.