Maximizing Reproductive Success Is individualistic Reproductive “strategy” – behavior that enhances an individual’s reproductive success Different strategies for males & females

Infanticide as a Reproductive Strategy Among Hanuman Langurs Bachelor males raid established group Fight w/dominant male Infants are killed Triumphant male takes over Brings females back into estrus Ensures babies are his

Primate Dominance Hierarchies Ranking of individual primates in a group based on their ability to displace, intimidate or defeat other group members through contests Low ranking (subordinate) and high ranking (dominant) individuals Dominance = preferential access to resources (both food and mating partners) Rank is not permanent (changes throughout life) Sex Age Time in group Level of aggression (challenging or “displaying”) Intelligence (Mike the chimp rolling cans in camp) Mother’s social position

Primate Dominance Hierarchies, cont. Associated with distinct behaviors & gestures Facial expressions communicate important social information

Dominance Hierarchies What they do: Control behavior and impose order Set of dominant and submissive behaviors Dominant behaviors = “displaying,” “mounting” Submissive behaviors = grooming high ranking indiv., “presenting” hindquarters Reduce violence within the group

Grooming Most important social activity Reinforces social bonds and status Restores harmony Helps form alliances

What Sets Humans Apart Locomotion – only primate that is habitually bipedal Anatomical changes/differences to support: Pelvis, legs, arms, foot bones Large, complex brains Rely on culture as primary means of adaptation Spoken language Linguistic ability provided an evolutionary advantage Reduced body hair Reproductive behavior – engage in sexual activity for non-reproductive purposes (like bonobos)