sentence: Homosexual behaviour is widespread among animals.
sentences_before: Homosexual behaviour has also been seen in animals. Homosexual, transgender and bisexual behaviour includes sex, courtship, affection, pair bonding, and parenting.
sentences_after: Bruce Bagemihl did research in 1999. It shows that homosexual behaviour has been observed in close to 1500 species, from primates to gut worms, and is well documented for 500 of them.
concept_name: homosexual behaviour
headings: Homosexuality Homosexual behaviour in animals