Schizophrenia Research Trends

126Joseph Polimeni and Jeffrey P. Reisscolony takes on the characteristic of a self-sustaining organism – sometimes described as asuperorganism.Animals that compete in groups tend to share a set of qualities not readily observed insolitary creatures. Whether a particular trait is best explained by individual, kin or groupselection can be scientifically debated, however, the existence of three evolutionary traits –task specialization (also known as division of labor), complex communication and altruismcannot be satisfactorily explained by individual models of selection. Furthermore, these traitsare never prominently observed in animals that don’t live in close-knit groups. Taskspecialization is a very prominent trait of eusocial insects. Leafcutter ants, for example, aredivided into a number of castes such as foraging workers, gardeners, and soldiers [79]. Anexample of complex communication is the waggle dance of honeybees. Compared to thebehavioral repertoire of solitary insects, waggle dances represent a form of communicationunprecedented in complexity – only the communication observed in a few mammals is moresophisticated. As for altruism, soldier ants that risk their lives to protect others or thepresence of sterile worker castes in honeybee colonies are two well-known examples.Extreme genotypic variability within a species is rare. For example, all frogs of the samespecies tend to be anatomically and behaviorally similar. Genetic variation does exist buttypically on a narrow spectrum. Uniform selection pressures tend to homogenize individuals– optimum traits get selected with the greatest frequency . In contrast, group-selected traitscan be sizably divergent. For example, some soldier ants can be 300 times heavier thangardener workers of the same species [79]. In addition to anatomical differences, thesesoldier ants behave differently than their more docile counterparts. The propagation of taskspecialists seems to be both genetically and environmentally determined [80-81]. It nowappears that group level specialization may not be exclusive to insects. In South Africanmole-rat colonies, two separate castes of breeding females with clear morphologicaldistinctions have recently been discovered [82].Human beings are similar to eusocial insects in many ways. The various primateancestors of Homo sapiens have lived in distinct groups for millions of years. Human beingsand eusocial insects share several phenotypic traits inadequately explained by mechanisms ofindividual selection [83]. Examples include, altruism, complex communication, apredisposition for organized warfare and hierarchal social structure. For man, the list of traitspoorly explained by individual selection could be extended to incorporate religion[84], ritual,humor and music. Thus, the evolutionary forces of group selection may have shaped thedevelopment of many cognitive skills.The genetics of group selection are essentially unknown. Task specialists couldconceivably be maintained by two types of balanced polymorphism – specifically,heterozygote advantage and assortative mating. Using the sickle-cell anemia example,heterozygote advantage could maintain individually disadvantageous traits in thecorresponding homozygotes. If the individually disadvantageous trait was altruistic, it wouldbe a group-selected trait ipso facto. Thus, a group selection evolutionary mechanism canwork synergistically with a kin selection paradigm. As for assortative mating, Wilson andDugatkin write, “Assortative interactions can generate highly nonrandom variation amonggroups, favoring the evolution of altruism and other group level adaptations amonggenealogically unrelated individuals” [85]. An example would be altruists having a