The Social Conquest of Earth by Edward O. Wilson

Author:Edward O. Wilson [Wilson, Edward O.]
Language: eng
Format: epub
Tags: General, Social Science, Sociology, Science, Anthropology, Philosophy & Social Aspects, Biology, Evolution, Life Sciences, Fiction, Nature, Ecology
ISBN: 9780871404138
Publisher: Liveright
Published: 2012-04-09T00:00:00+00:00

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The Emergence of a New Theory of Eusociality

THE EVOLUTIONARY ORIGIN of any complex biological system can be reconstructed correctly only if viewed as the culmination of a history of stages tracked from start to finish. It begins with empirically known biological phenomena in each stage, if such is known, and it explores the range of phenomena that are theoretically possible. Each transition from one stage to the next requires different models, and each needs to be placed in its own context of potential cause and effect. This is the only way to arrive at the deep meaning of advanced social evolution and the human condition itself.

The first conceivable stage in the origin of eusociality, entailing division of labor that is seemingly altruistic, is the formation of groups within a freely mixing population of otherwise solitary individuals. There are in theory many ways in which this might occur in reality. Groups can assemble when nest sites or food sources on which a species is specialized are local in distribution, or when parents and offspring stay together, or when migratory columns branch repeatedly before settling, or when flocks follow leaders to known feeding grounds. They might even come together randomly by mutual local attraction.

The way in which groups are formed probably has a profound effect on the likelihood of progress toward eusociality. The most important way includes the tightening of group cohesion and persistence. For example, as I have stressed, all of the evolutionary lines known with primitively eusocial species surviving (in aculeate wasps, halictine and xylocopine bees, sponge-nesting shrimp, termopsid termites, colonial aphids and thrips, ambrosia beetles, and naked mole rats) have colonies that build and occupy defensible nests. In a few cases, unrelated individuals join forces to create the little fortresses. Unrelated colonies of Zootermopsis angusticollis, for example, fuse to form a supercolony with a single royal pair through repeated combats. In most cases of animal eusociality, however, the colony is begun by a single inseminated queen (for instance in the Hymenoptera) or mated pair (termites). Therefore, in most cases the colony grows by the addition of offspring that serve as nonreproductive workers. In a few, more primitively eusocial species, the growth is hastened by the acceptance of alien workers or by the cooperation of unrelated founding queens.

Grouping by family can accelerate the spread of eusocial alleles, but it does not of itself lead to advanced social behavior. The causative agent of advanced social behavior is the advantage of a defensible nest, especially one expensive to make and within reach of a sustainable supply of food. Because of this primary condition in the insects, close genetic relatedness in primitive colony formation is the consequence, not the cause, of eusocial behavior.

The second stage is the happenstance accumulation of other traits that make the change to eusociality still more likely. The most important is close care of the growing brood in the nest—by feeding the young progressively, or cleaning the brood chambers, or guarding them, or some combination of the three.

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