1. Maximizing Reproductive 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)