Zoophilia of bestiality is partly caused by irrational speciesism and anthropocentrism. Because interspecies sex occurs in nature, and because humans "are" animals, supporters argue that zoosexual activity is not "unnatural" and is not intrinsically wrong. Research has proven that non-human animals can and do have sex for non-reproductive purposes (and for pleasure). In 2006, a Danish Animal Ethics Council report concluded that ethically performed zoosexual activity is capable of providing a positive experience for all participants, and that some non-human animals are sexually attracted to humans (for example, dolphins). Some zoophiles claim that they are not abusive towards animals: "In other
Sex cases, an asymmetry has evolved such that two different types of gametes (heterogametes) exist (known as anisogamy). Physical differences are often associated with the different sexes of an organism; these sexual dimorphisms can reflect the different reproductive pressures the sexes experience. For instance, mate choice and sexual selection can accelerate the evolution of physical differences between the sexes. Among humans and other mammals, males typically carry an X and a Y chromosome (XY), whereas females typically carry two X chromosomes (XX), which are a part of the XY sex-determination system. Humans may also be intersex. Other animals have different sex-determination