MORPHOLOGY AND BIOLOGY OF REPTILES

Abstract

tion. Since nine-banded armadillos are born in litters of genetically identical quadruplets, there is no genetic variation within families. Therefore, there can be no selection within families as a result of interactions between sibs. The hypothetical evolution of strong sib altruism in the nine-banded armadillo would have to occur by selection at the family level operating upon the between family variation for the appropriate behaviors. Dawkins' misconception of the role of population structure in the evolution of social behaviors stems from his confusion of the effect of selection with the process of selection. He reasons as follows (chapter 3): Because evolution consists of changes in gene frequency and because genes persist unchanged longer than chromosomes, genomes, or gene pools, the gene must therefore be the unit of selection. Since genes reside on the chromosomes of individuals, all forces which affect gene frequencies can be reduced to increments or decrements in the fitness of individuals as a matter of mathematical convenience. This reductionist approach (employed by Hamilton in his mathematical formulation of kinship theory), however, does not mean that all selective changes can be attributed strictly to selection at the genic level. The differential proliferation of the various units of population structure can be the actual mechanism of gene frequency change. And, it is the variance between the units of population structure which determines the relative rates of gene frequency change caused by selection at any level. These aspects of population structure are of special interest in the study of the evolution of social behaviors because population structure per se can permit the evolution of traits which would be selected against in randomly mating and mixing populations. In addition to these shortcomings, many of Dawkins' arguments approach circularity as, for example, his discussion of why some male elephant seals win and hold harems. Harem holders tend to win these fights against would-be usurpers, if only for the obvious reason that that is why they are harem holders. Usurpers do not often win fights, because if they were capable of winning they would have done so before! (p. 173). In short, usurpers do not often win fights, because usurpers do not often win fights. I do not believe that arguments of this type can assist the average layperson in understanding the process of evolution by natural selection. Instead, I fear that arguments of this nature will add more anecdotes to that body of misconceptions known as the common wisdom.