The underlying theme uniting the papers of this volume is the quest for a further understanding of human behavior. The similarities between the behaviors of other primates and humans have captivated us even before a science arose. But what is the justification for making such comparisons? Comparisons, like classifications, can be made on any basis whatever. The aim in making any scientific comparison is the same as doing a classification. That is, one attempts to make the comparison on a "natural" basis. Natural, in this case, means that the comparison reflects processes that occur in nature....