In biology[edit] Ultimate causation explains traits in terms of evolutionary forces acting on them. Example: female animals often display preferences among male display traits, such as song. An ultimate explanation based on sexual selection states that females who display preferences have more vigorous or more attractive male offspring. Proximate causation explains biological function in terms of immediate physiological or environmental factors. Example: a female animal chooses to mate with a particular male during a mate choice trial. A possible proximate explanation states that one male produced a more intense signal, leading to elevated hormone levels in the female producing copulatory behavior. Although the behavior in these two examples is the same, the explanations are based on different sets of factors incorporating evolutionary versus physiological factors. These can be further divided, for example proximate causes may be given in terms of local muscle movements or in terms of developmental biology (see Tinbergen's four questions). - http://en.wikipedia.org/wiki/Proximate_and_ultimate_causation