 Evidence for this view is the reduced sexual dimorphism in the early stages of human evolution, particularly the loss of the aggressive canine morphology evident in other extant primate taxa.The theory postulates an intensification of maternal care, and associated increased pro-social behaviour of offspring, as being the distinguishing feature of the human lineage.His theory echoes that of Adrienne Zihlman, who postulated changes in patterns of sub-adult socialisation may have been important in the early stages of human evolution.