Mechanisms for recognizing kin are found throughout the plant and animal kingdoms, regardless of an organism's social or mental complexity. Improvements in the general understanding of these mechanisms have turned some biologists' attention to the question of why kin recognition occurs at all. One response to this question is offered by the the honeybee, most of whose members do not produce offspring and exist only to nurture relatives.
Inclusive fitness theory has also been applied usefully to new findings concerning cannibalism within animal species. Based on the theory, cannibals should have evolved to avoid eating their own kin because of the obvious genetic costs of such a practice. Spadefoot toad tadpoles provide an illustration. Biologists have found that all tadpoles when it becomes very hungry, apparently putting its own unique genetic makeup ahead of its siblings'.
But there may be other reasons why organisms recognize kin. For example, it has recently been found that tiger salamander larvae, also either omnivorous or cannibalistic, are plagued in nature by a deadly bacterium. Furthermore, it was determined that cannibal larvae are especially likely to be infected by eating diseased species members. which an organism preserves its own life, not as a means to aid in relatives' survival.
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