Lec 25

ANT 001: Human Evolutionary Biology - Week 10: Cooperation

• Instructor: Prof. Brenna Henn

• Winter Q 2025

Key Questions from Last Class

• Infanticide occurs when new males become dominant in a group due to changing social structures and hierarchy.

• Inbreeding avoidance happens because homozygous genotypes can lead to reduced fitness or detrimental phenotypic effects.

• Statement regarding Himba’s marriage system and ‘extra pair paternity’ is true, reflecting social dynamics.

Class Updates

• Chapter readings: Chapters 7, 16.

• Final Exam Study: Study guide and Jeopardy review available.

• Final Exam:

  • Date: March 19th, Time: 6-8 PM

  • Location: Young Hall 198.

  • Bring a pencil; typed/written notes are allowed but no electronics.

• Writing Assignment #3 due electronically on Canvas by noon, March 19th; normal essay format accepted.

Altruism: A Puzzle

• Definition of Altruism:

  • Involves helping others at a personal cost.

• Reciprocal Altruism:

  • Benefits both parties over multiple interactions.

• Mutualism:

  • Behavior where both participants gain benefits.

• Kin Selection:

  • Explains altruism through aiding biological relatives.

Mutualism

• Definition:

  • Benefits both participants involved in mutualistic relationships.

• Vulnerability to Cheaters:

  • If individuals receive rewards without costs, mutualism fails to persist.

Mutualism: Baboons

• Medium-ranked baboons mate-guard females together, enhancing reproductive success for both.

• Collaborative behavior is crucial; failure to cooperate can lead to mutual reproductive failure.

Kin Selection

• Proposed by W. D. Hamilton (1964).

• **Key Concepts: **

  • Group members share different levels of genetic relatedness.

  • Altruism may evolve by benefitting relatives in the group.

  • Altruistic acts such as alarm calls may be costly but benefit shared genes.

Evolution of Menopause

• Grandmothering Hypothesis:

  • Highlights kin selection; grandmothers aid in the care and reproduction of their children's offspring.

• Reasons for Menopause:

  • Competition for resources among offspring; reduced potential to bear additional children due to age.

  • Genetic advantages for longevity versus chromosome repair challenges.

Cooperation is Pervasive

Cooperation and Warfare

• Cultural Context:

  • Turkana in northern Kenya practice cattle pastoralism requiring large grazing lands, leading to inter-group raiding.

  • Violence during conflicts often results in serious implications, including death.

Cooperation and Warfare Continued

• Turkana fighters may not know each other, challenging traditional concepts of reciprocal altruism.

• Motivation for cooperation includes acquiring livestock and territories.

Cooperation and Punishment

• Consequences of Cheating:

  • Cheating warriors face punitive measures: verbal scolding, physical punishment, and loss of livestock.

  • Reputation and social standing are critical; negative perceptions affect mating opportunities.

  • Third-party sanctions play a role in maintaining cooperative behavior across various societal norms.

Cooperation: Mismatch Hypothesis

• Human psychology evolved for cooperation in small-scale societies with closely related individuals.

• This evolved capacity remains relevant, but challenges arise in large groups with unrelated members.

Cooperation: Cultural Group Selection

• Cultural Dynamics:

  • Rapid cultural adaptation influences large-scale cooperation.

  • Different tribal norms impact success in competing with neighboring cultures through collective effort.

  • Nuer tribes effectively form larger war parties, out-competing Dinka cultural practices, which diminish.

What Makes Us Human?

• Key characteristics:

  • Clothing

  • Language

  • Tools

  • Fire

  • Bipedalism

  • Cooperation

  • Body modifications

  • Long childhood

  • Menopause

  • Medicine

  • Running

Learning Objectives

• Understanding:

  • Evolution processes: mutation, natural selection, genetic drift, migration.

  • Key concepts in hominin evolution: fossil evidence, timelines, derived traits.

  • Primate diversity, attitudes towards genetics, and evolution of culture.

• Skill Outcomes:

  • Ability to interpret scientific evidence and evaluate competing hypotheses.

  • Demonstrate scientific knowledge in writing.

Questions?