After 51 researchers in six countries studied the genomes of a half-million people, they found that genes play an identifiable role in same-sex sexuality for no more than about one third of the people studied. Even for this subset, the identified causal relationship was very small. Altogether, the study reported, the genetic correlations they identified are so weak that they “do not allow meaningful prediction of an individual’s sexual preference.
”Instead, according to the researchers themselves, “non-genetic factors — such as environment, upbringing, personality, nurture — are far more significant in influencing a person’s choice of sexual partner, just as with most other personality, behavioral and physical human traits.”