Animal sexual behaviour however, is proving to be false as, "most hormones don’t influence behaviour directly. Rather, they affect thinking and emotions in variable ways (Azar, 40)." There is much more involved in sexual behaviour in the mammalian animal than oxytocin and vasopressin can explain. It is often assumed that animals do not have sex for pleasure, or alternatively that humans, pigs, bonoboes (and perhaps dolphins and one or two more species of primates) are the only species that do. This is sometimes stated as "animals mate only for reproduction". This view is considered a misconception by some scholars. Jonathan Balcombe argues that
Men who have sex with men with men since 1977 have an HIV prevalence (the total number of cases of a disease that are present in a population at a specific point in time) 60 times higher than the general population". In 2007, the largest estimated proportion of HIV/AIDS diagnoses among adults and adolescents in the U.S. were men who have sex with men (MSM). While this category is only 2% of the U.S. population they accounted for 53% of the overall diagnoses and 71% among men. According to a 2010 federal study, one in five men who have sex with men are HIV positive and