Thus Leavitt's stated goal is not his actual destination, and his rejection of a sociobiological theory is accomplished without considering most of the relevant biological and ethological literature of the last decade. A second problem is that there are a number of missleading statements in the presentation of material he does consider. If all anthropologists read widely in these fields, the paper would be read for its good points, these errors quietly forgotten. Since incest avoidance is one of anthropology's central problems, a comment on some of those errors seems worthwhile. By analogy he presumably would argue that the existence of a secular trend in adult height demonstrates the absence of any genetic influence on stature.
Space precludes full discussion of factors that can promote incestuous behavior.
Unreduced levels of heterozygosity and genetic loads approaching zero are simply incompatible. There are also problems with the representation of articles he does discuss. This hardly sounds like sexual aversion, but mother-son nonreproductive sexual behavior is still consistent with a sociobiological framework. If nonhuman primates can be allowed psyches, the psychological aspects of such behavior should prove a fascinating area for study. In fact, the average FIS is negative which indicates that close inbreeding is actually avoided.