Causes: Inborn (Nature)
Is there a "gay" gene?
Do studies conducted on homosexuality in twins show a genetic basis of sexual orientation?
Can hormones affect sexual orientation?
Does the fraternal birth order effect demonstrate a biological basis to sexual orientation?
Are there physical differences in the brain structure of heterosexual and homosexual people?
Is there a connection between sexual orientation and handedness?
Is there a connection between sexual orientation and the ratio between second and fourth finger length?