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Anthropology Week 6 Notes

by: Amanda Notetaker

Anthropology Week 6 Notes ANTH 160

Marketplace > University of New Mexico > Anthropology > ANTH 160 > Anthropology Week 6 Notes
Amanda Notetaker
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About this Document

This week covers the beginning of lecture 5 on reciprocal altruism
Human Life Course
Dr. Tanya M. Meuller
Class Notes
Anthro, Anthropology, week, 6, notes, Human, life, course
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This 7 page Class Notes was uploaded by Amanda Notetaker on Thursday September 29, 2016. The Class Notes belongs to ANTH 160 at University of New Mexico taught by Dr. Tanya M. Meuller in Fall 2016. Since its upload, it has received 5 views. For similar materials see Human Life Course in Anthropology at University of New Mexico.


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Date Created: 09/29/16
Anthropology 160.001 The Human Life Course Week 6 Readings: Kaplan et al. (2000) A Theory of Human Life History Evolution: Diet, Intelligence and Longevity (Learn)Trivers: Chapter 9, Parental Investment and Sexual Selection (Learn)Low, Chapter 3, The Ecology of Sex Differences, pp 35-56 (Tuesday Thursday September 25, 27): Evolution of the Human Life Course, Productivity and Consumption; Parental Investment, Sexual Selection and Resource Competition; Film N!ai!: Story of a !Kung Woman 9/27 Before the exam we discussed: How cooperation occurs among genetic relatives How do we explain cooperation among unrelated individuals? New lecture: Evolution of Cooperation Kin selection: cooperate or aid because it increases inclusive fitness Mutualism: cooperate because there is a net survival or reproductive benefit to both individuals by doing so Manipulation: what looks like altruism on the part of the donor may in fact be manipulation by the recipient Ex: brown headed cowbirds that lay eggs in the nest of another species Reciprocity: Evolution of Reciprocal Altruism  True altruism requires that the donor pay a cost so that the recipient gains a benefit  When the donor and the recipient change roles sequentially the process is called reciprocal altruism -First proposed to explain cooperation among non-kin -Trivers (1971) was credited with the first explicit dialogue Definition: The non-simultaneous exchange of resources -Resources characterized by diminishing returns curve are perfect for explaining altruism Trivers says reciprocal altruism will only be stable and favored by natural selection if: 1. Asynchrony of abundance and “need” or time or resources  You need what I have at a certain time, or I need what you have at a later time 2. Benefits outweigh costs to both individuals  Diminishing returns with resource amount  Asynchronous changes in value through time 3. Many future interactions over unspecified time  Long lifespan Low dispersal rates 4. Ability to detect cheaters and withhold benefits from them  Can detect opportunities for reciprocation The less you have, the greater impact 1 unit of gain will have. The more you have, the less impact 1 unit loss will have. *Proportion of quantity given is what matters, not the actual amount of how much is given. Problems with Reciprocal Altruism:  Delayed return benefits o Effects degree of balance in payment o Provides opportunity for cheating or defecting Types of reciprocity: Generalized: where you give widely Balanced: true one-for-one relationship Negative: payday / loan situation Game Theory: analytical tool used to solve what the optimal response will be when the payoffs are frequency dependent (when the costs and benefits of a given action depend on what the other actors do) Negative frequency dependent situations: more people yield less benefit Example: how many people win a jackpot Positive frequency dependent situations: more people yield a bigger benefit Example: inviting people to a party. Evolutionary Stable Strategy: a strategy that leads to the highest payoff no matter what others do. Such a strategy cannot be invaded by any other alternative strategy. Modeling Reciprocal Altruism: The Prisoners Dilemma: Imagine there are two prisoners who have been picked up as suspects for a crime. They are separated and the police offer each a reduced sentence if they will implicate the other (their partner) in the crime. Prisoners dilemma is any payoff matrix with the rewards such that: T > R > P > S T: temptation R: reward P: punishment S: suckers  Both keep mouth shut à may not be convicted if the police have a weak case – receive payoff R which is the reward for cooperation (a low, but still non-zero chance of going to jail)  If one squeals on partner à he serves one year (or goes free) and the partner gets the harshest sentence – the squealer’s payoff is T the temptation to defect (T>R since there is no chance of going to jail)  If one keeps quiet while the other confesses à one that doesn’t squeal goes to jail and gets the payoff S, the sucker’s payoff (lowest possible outcome since the full weight of the law comes down on him alone and he is convicted due to his partner’s evidence  Both confess à payoff P (punishment) which is higher than S (since they helped the police), but still lower than T or R since they will serve some jail time There are two players, each with two choices (C or D) Each player has two choices: cooperate or defect They make choices without knowledge of the other player’s choices Goal of each player is to maximize his/her payoff T=4, R=3, P=2, S=1 T>R>P>S R>(T+S)/2 The optimal strategy is for both players to defect The dilemma is that even though the optimal strategy is for both players to defect, they would both do better if they both cooperated. How does cooperation emerge? Axelrod and Hamilton (1981) were interested in both the emergence and subsequent evolution of cooperation in a world in which defection was the primitive state To examine the evolution in such a world, Axelrod and Hamilton used a two-pronged attack: 1. Axelrod ran computer tournaments in which participants submitted a strategy in the form of a computer program and strategies competed against one another in games that lasted 200 moves 14 strategies submitted, and each strategy faced itself and all others…Tit-For-Tat submitted by Anatol Rapoport won 2. Ran another tournament that contained a wider variety of submitted strategies (62 in all) *This tournament was an ecological tournament After the initial round-robin, a second “generation” is simulated in which strategies exist in proportion to their success in the original round robin, and this process is iterated over time to determine which strategies would evolve in the long run. Once again, Tit-For-Tat emerged as the winner. Tit-for-Tat Nice: always starts as cooperative Retaliatory: punishes non-cooperators Forgiving: goes back to cooperating if the other player does **This is an example of reciprocal altruism (one-for-one) TFT1: individual A provides a benefit to B and incurs a cost at time 1 TFT2: individual B provides a benefit to A and incurs a cost at time 2 D: defects always What conditions foster reciprocity altruism?  Good memory for score-keeping –punish defectors and reward cooperators  “Shadow of the future” –relatively long-term interactions with partners Evidence of reciprocal altruism in other species: Vampire bat food sharing (Wilkinson 1984) *If they have two failed feeding nights they will die (3 days) *The probability of not starving to death in a given year is 0% for juveniles and 16% for adults *FOOD SHARING: regurgitate blood Reciprocators give to bats that are more in need. The time to starvation curve shows correct form that individuals with food give up less survivorship than they gain when they are shared with.  Groups of adult females consist partly of kin, but overall level of relatedness is 0.1  Females associate closely over long periods of time, often for more than two years and sometimes for more than eleven  Degree of association between two bats as a strong predictor of the degree to which one bat will regurgitate blood to another (no regurgitation unless association of 60% or more)  This effect in addition to independent kinship effect of about the same magnitude NOTE: class on 9/29 was cancelled due to a family emergency. Lecture will resume next week.


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