Homosexual Behaviour in Animals: An Evolutionary Perspective - Paperbackby Volker Sommer (Editor), Paul L. Vasey (Editor) Behavioural observations from both the field and captivity indicate that same sex sexual interactions are widespread throughout the animal kingdom, and occur quite frequently in certain non human species. Proximate studies of these phenomena have yielded important insights into genetic, hormonal and neural correlates. In contrast, there has been a relative paucity of research on the evolutionary