Maximizing Reproductive Success

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

2. 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

3. 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

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

5. 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

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

7. 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)