The Evolution of Eusociality [from 'The Biology of the Naked Mole Rat']

Eusociality is a remarkable topic in evolutionary biology. The term, introduced by Michener (1969), refers to species that live in colonies of overlapping generations in which one or a few individuals produce all the offspring and the rest serve as functionally sterile helpers (workers, soldiers) in rearing juveniles and protecting the colony. The wasps, bees, ants, and termites known to live this way had previously been called the "social" insects. The recent discovery of eusociality in aphids and naked mole-rats has provided biologists with new impetus to understand more fully the origins and selective background of this phenomenon, which has already played a central role in the analyses of sociality in all animals and, indeed, of evolution itself. These two new instances both broaden the search for correlates of eusociality in the widely different groups in which it has evolved independently and stimulate comparative study of related species of insects and vertebrates with homologous behaviors verging on eusociality. An unusual and complicated form of sociality has thus evolved independently in four different groups, and in one, the Hymenoptera, has persisted from perhaps a dozen independent origins. Explaining this phenomenon requires attention to a number of different questions. Darwin answered the basic one, How can natural selection produce forms that would give up the opportunity to reproduce, instead using their jives to contribute to the success of the offspring of another individual [Adapted from the author's preamble] *** This volume brings together more than a decade of information collected in the field and lab on the naked mole-rat (Heterocephalus glaber), a northeast African mammal unique for its physical characteristics and eusociality. Nearly blind and virtually hairless, naked mole-rats inhabit large subterranean colonies in which only one female and her one to three mates conceive offspring, while the young from previous litters maintain and defend the group as do workers in colonies of the social insects. In this first major treatise on naked mole-rats an international group of researchers covers such topics as the evolution of eusociality, phylogeny and systematics of the rodent family Bathyergidae, population and behavioral ecology and genetics of naked mole-rats in the field, vocal and nonvocal behaviors, social organization and divisions of labor within colonies, and climatic, social, and physiological factors affecting growth, reproduction, and reproductive suppression. [Publisher's description for the book]