Living things are constantly engaged in a struggle for existence, and ingenious devices for the purpose of self-preservation can be seen in all types of animal and plant life. However, nature also displays phenomena that are not related to survival or that seem clearly to violate the principle of self-preservation--particularly when organisms interact with one another. Darwin investigated these apparent contradictions and proposed that both mechanisms of self preservation and those of reproduction are explained by a more basic principle of "natural selection"--the reproductive survival of the fittest. George C. Williams in Group Selection challenges the adequacy of this process of selection at the individual level.

Williams has here collected the work of the chief partisans with opposed viewpoints on the theory of selection at the group level to state their arguments and rebuttals. A minority of modern biologists offer evidence to show that groups of living things are organized to assure their collective survival; they are not merely collections of individuals designed for their own survival and reproduction. In opposition, defenders of the traditional point of view charge that mechanisms of group survival are based on illusion and misinterpretation.