• Choose a category
• All
• Classic-Fiction

In these days when biology has become highly mathematical, the views of mathematical evolutionists have great weight, despite their disagreements. Many years after Darwin, Sewall Wright (1949) concluded that the subdivision of a species into partly isolated groups, or demes, between which there is limited interbreeding with resultant flow of genes, "provides the largest store of variability both locally and within the species as a whole, and by providing for selection in which whole genetic complexes are the objects, frees evolution most completely from dependence on rare favorable mutations and makes possible the most rapid exploitation of an ecologic opportunity." Elsewhere Wright (1940) wrote: "A local population that happens to arrive at a genotype that is peculiarly favorable in relation to the general conditions of life of the species . . . will tend to increase in numbers and supply more than its share of migrants to other regions, thus grading them up to the same type by a process that may be described as intergroup selection."

Another mathematical evolutionist whose writings are often quoted, R. A. Fisher (1958) denied the effectiveness of group selection, even in humans, who for ages lived in small, mutually hostile groups to which Wright's model might apply, and until quite recently continued to exist in this manner in vast areas of Amazonian forests. "The selection of whole groups," he wrote, "is, however, a much slower process than the selection of individuals, and in view of the length of the generation in man the evolution of his higher mental faculties, and especially of the self-sacrificing

Page 149

element in his moral nature, would seem to require the action of group selection over an immense period.'' In answer to this objection, we might remember that the evolution of man from prehuman hominids required at least two million years, or about a hundred thousand generations. Until modifications that spring up in individuals become firmly established in a population, however long this might take, evolution has not occurred. Fisher denied that "the principle of Natural Selection" affords a rational explanation "for any properties of animals or plants which, without being individually advantageous, are supposed to be of service to the species to which they belong." This is no argument against group selection, which does not require self-sacrificing activities but rather cooperation that benefits all participants, as in mutual defense, the search for food, the construction by groups of avian apartment houses in which many individuals nest and sleep, cooperative breeding, and among plants that grow gregariously, the maintenance of a habitat or microclimate in which they thrive better than when growing alone. Moreover, as pointed out in chapter 2, reproduction itself entails a sacrifice of the individual for the benefit of its species.

Group selection may transcend specific boundaries. The group favored by selection may consist of animals of two kinds that become mutually dependent, or of an animal and a plant, as occurs when a flower becomes specialized for pollination by one species of insect or bird, which in turn becomes highly modified for extracting nectar from that particular kind of flower. Unless the modifications of pollinator and flower keep pace with one another, such coevolution could not occur.

An inappropriate term can cause widespread confusion. Impressed by the results of human selection of domestic animals and plants, Darwin chose the term natural selection for a superficially analogous process in wild nature. Artificial selection and natural selection differ profoundly. An intelligent breeder of plants or animals takes special care of individuals that vary in a desired direction; nature does nothing of the sortwithout pampering the more fit, it ruthlessly eliminates the less fit. Not surprisingly, many of Darwin's

Page 150

early critics (like not a few later ones) were perplexed