fundamental kinship relations of donor and recipient (Rosenberg, 1992). Altruism has since been generalized to include any form of nonselfish behavior and serves as the cornerstone for much of sociobiology (Wilson, 1975). In this sense, altruistic behavior includes care-giving to kin other than an individual's direct offspring. Feeding, protecting, warning, defending, and teaching kin, in proportion to their consanguinity, emerges as an adaptationally optimal strategy for older individuals.

Many forms of altruism are evident within social species. Maxim (1979) lists four altruistic roles of aging in primates: (1) defense of territory, (2) defense against predation, (3) control of troop movement, and (4) aunt behavior. These activities are of little or no direct benefit to the elderly individuals but do serve to directly benefit the kinship community. Further, Medawar (1957) comments that altruistic behavior of grandparents should be indirectly selected for because, although grandparents are infertile and their behavior is of no benefit to themselves, "grandmotherly indulgence" does benefit the community. Hamilton (1966) also proposed that postreproductive life spans may have evolved when the older animal benefits its younger kin. For example, old postreproductive female langurs ardently defend their troops and protect troop infants to a much greater degree than younger females (Hrdy, 1981). Also, Norris and Pryor (1991) suggest that many postreproductive, yet still lactating, females in dolphin societies may be present as a source of nourishment to offspring of younger mothers while those mothers dive to great depths for prey. Diamond (1996) supports the occurrence of altruistic postreproductive females by stating that aging human females can, evidently, "do more to increase the number of people bearing her genes by devoting herself to her existing children, her potential grandchildren, and her other relatives than by producing yet another child."

An example of altruism in a nonsocial species is given by Blest (1963). Blest found that cryptic New World Saturnid moths, which rely on camouflage to escape detection but are quite palatable to predators, die shortly after completing reproduction. The aposematic subgroup of New World Saturnid moths, which rely on their terrible taste to discourage predators, exhibit a long postreproductive period. Postreproductive survival of the tasty moths is detrimental to conspecifics because a predator can establish a search image of the cryptic species by feeding on palatable individuals. However, a predator's unpleasant experience with an aposematic individual would benefit its kin and other conspecifics. Thus, Blest argued that the sustained physical fitness of postreproductive aposematic moths contributes to the survival of the younger reproductives.

Dominance and Leadership

To dominate is to possess priority of access to the necessities of life and reproduction (Wilson, 1975). Understanding the governance of animal societies by dominance hierarchies provides the fundamental basis for studying the behav-



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