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fact, they are fantastically successful, particularly the ants and termites, but also the bees and wasps (Wilson, 1987). Success can be measured as current ecological success, e.g., geographic diversity, species richness, and biomass. Ants are very speciose and are native to all terrestrial habitats except Antarctica, Iceland, Greenland, and a few remote islands (Wilson, 1987). At one thoroughly studied location in the Amazonian forest, social wasps, ants, bees, and termites make up four-fifths of all insect biomass and over a fifth of all animal biomass (Fittkau and Klinge, 1973).

Success can also be measured in evolutionary antiquity, staying power, and diversity. Social insects are represented in the fossil record by impressions of their bodies and their nests. The fossils of bodies are most useful for tying these insects to extant lineages, whereas the fossil nests demonstrate clear evidence of ancient sociality. Body fossils of presumably social termites, ants, bees, and wasps are found in the Cretaceous, whereas nest fossils are found for some lineages as early as the Triassic (Grimaldi et al., 1997; Hasiotis, 2003; Bordy et al., 2004). Only an origin before the breakup of Pangaea in the late Triassic is consistent with the worldwide extent of major social insect lineages. The dispersion of major social insect lineages was essentially complete before the high sea levels of the Late Cretaceous isolated many land masses 100 Mya (Hasiotis, 2003; Bordy et al., 2004). Another indication of the evolutionary robustness of the social habit is the absence of clear evidence for major lineages of social insects that subsequently went extinct (Wilson, 1987).

AN INORDINATE FONDNESS FOR KINSHIP

Any theory of adaptation or design ought to explain why social insect groups are so well adapted while most groups of multicellular organisms are not adapted. Perhaps the most common feature of insect societies, aside from their cooperation, is that they are family groups. In some species, colonies are headed by one singly mated queen (or in termites, a queen and a king), and all other colony members are full siblings. In others, the degree of relatedness is lower, but it is nevertheless substantial in all but a few species of unicolonial insects that are recently derived from those with higher relatedness. The high relatedness within colonies is often enforced by overt kin recognition: nonrelatives are recognized and rejected. Haldane once quipped that nature suggests that the creator must have had an inordinate fondness for beetles. With respect to superorganisms, there also seems to be an inordinate fondness for kinship ties among cooperators.

Darwin had at least an inkling of this: “As with the varieties of the stock, so with social insects, selection has been applied to the family, and not to the individual, for the sake of gaining a serviceable end” (Darwin, 1872, p. 230). But the idea was not formalized until W. D. Hamilton’s work



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