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  • 1. Moral Apes
  • 2. The Evolution of Cooperation
    • Individual Selection:
      • Many apparently altruistic acts actually benefit the “helper”
      • There is a direct benefit to working together
  • 3.
    • Some mouth-brooding cichlids are “parasitized” by other females; but actually gain fitness because their own offspring less likely to be prey
  • 4.
    • Male lion coalitions: larger groups are more successful at overthrowing resident males; hold onto prides longer. Not all males are related.
  • 5.
    • Orcas: optimal foraging size is 3. On average, per capita food intake is highest at this group size.
  • 6.
    • Long-tailed manakins: two males dance, one male mates. “
    • “ Apprentice” learns dance and may inherit “mentor’s” territory
  • 7.
    • Belding’s ground squirrel: “aerial predator” alarm call creates confusion; alarm callers preyed upon less than non-callers
  • 8.
    • What about when there is no direct benefit?
      • What benefit do parents get for investment in children?
      • What benefit do siblings get for looking out for each other?
    The Evolution of Cooperation
  • 9. Children
    • Investment in children
      • “ Imagine two animals, otherwise identical, where only one is predisposed to care for its children in a way that increases their chances of survival. Whatever heritable properties cause this animal to be a caring parent will spread through the population, because the offspring of that animal will have a greater chance of surviving…”
      • Bloom, p.104
  • 10. Kin Selection/ Inclusive fitness
    • The theory
      • Reproductive success- leaving your genes to the future
      • Relatives other than your offspring share some of your genes; you can increase fitness by increasing survival/reproduction of relatives.
  • 11. Hamilton’s rule: rB >C
    • r = the genetic relatedness of the recipient to the actor.
    • B = the additional reproductive benefit gained by the recipient of the altruistic act,
    • C = the reproductive cost to the individual of performing the act.
    • This says that the cost must be less than the product of the benefit to recipient times the probability that the relatives have the same genes.
  • 12. Coefficient of Relatedness (r )
    • The proportion of genes shared by two individuals
    0.125 Cousin 0.25 Niece/nephew 0.25 Grandchild 0.25 Half sib 0.5 Full sib 0.5 Offspring r You and
  • 13. Kin selection
    • “ C” is the loss in expected personal reproductive success through the self-sacrificing behavior (jumping into a river).
    • “ B” is the increase in the relatives' expected reproductive success (by not drowning).
    • “ r” is the probability of genetic relatedness (brother, cousin).
    • Haldane: "I would lay down my life for two brothers or eight cousins".
  • 14. Within-Family Altruism
    • For this reason, in the expression rB > C, everything hinges on r.
    • The probability that the altruist's siblings carry copies of the same altruist gene.
    • Dawkins observed, "[k]in selection accounts for within-family altruism; the closer the relationship, the stronger the selection.”
  • 15. Limitations
    • The obvious limitation of Hamilton's Rule is that it only justifies altruism expressed within the family.
    • Alternative theories, such as reciprocal altruism, can account for the natural selection of generally cooperative behavior regardless of familial relationships.
  • 16.
    • Vampire bats: individuals may be related or unrelated. Females will feed females who have fed them, and reject those who have rejected them.
  • 17. But what about true altruism?
    • What about cases that can’t be explained in terms of genes or relatedness?
    • So what do we do with altruism?
  • 18. Darwin The Descent of Man (1871) “ The following proposition seems to me in a high degree probable – namely, that any animal whatever, endowed with well-marked social instincts, would inevitably acquire a moral sense or conscience, as soon as its intellectual powers had become well developed, or nearly as well developed, as in man” (chapter III, p71) “ Thus the social instincts, which must have been acquired by man in a very rude state, and probably even by his early ape-like progenitors, still give the impulse to many of his best actions” (chapter III, p86)
  • 19. The Prisoner’s Dilemma
  • 20. Game Theory
    • The Prisoner’s Dilemma was one of the earliest “games” developed in game theory. By simulating the Prisoner’s Dilemma we are given an excellent method of studying the issues of conflict vs. cooperation between individuals.
    • Since the Prisoner’s Dilemma is so basic, it can be used as a model for various schools of thought, from economics to military strategy to zoology, and even Artificial Intelligence.
  • 21. Robert Axelrod
    • Interested in political relationships and reproductive strategies in nature
      • Wanted to study the nature of cooperation amongst nations
      • He used the Prisoner’s Dilemma game as a model to help explain the evolution of cooperating species from an inherently selfish genetic pool
  • 22. PD as a Model of Nature
    • Accurate in the fact that an agent only cares about itself (It is naturally selfish)
    • Furthermore, cooperation can be mutually beneficial for all involved
  • 23. Game Setup
    • The Game:
      • Two people have been arrested separately, and are held in separate cells. They are not allowed to communicate with each other at all.
    • Each prisoner is told the following:
      • We have arrested you and another person for committing this crime together.
  • 24.
      • If you both confess, we will reward your assistance to us, by sentencing you both lightly: 2 years in prison.
      • If you confess, and the other person does not, we will show our appreciation to you by letting you go. We will then use your testimony to put the other person in prison for 10 years.
      • If you both don’t confess, we will not be able to convict you, but we will be able to hold you here and make you as uncomfortable as we can for 30 days.
  • 25.
      • If you don't confess, and the other person does, that person's testimony will be used to put you in prison for 10 years; your accomplice will go free in exchange for the testimony.
      • Each of you is being given the same deal. Think about it.
  • 26. Structure of the Game
    • If both players Defect on each other, each gets P (the Punishment payoff);
    • If both players Cooperate with each other, each gets R (the Reward payoff);
    • If one player Defects and the other Cooperates, the Defector gets T (the Temptation payoff), and the Cooperator gets S (the Sucker payoff);
  • 27. Structure of the Game - Cont’d
    • T > R > P > S and R > (T+S)/2.
      • These inequalities rank the payoffs for cooperating and defecting.
      • The condition of R > (T+S)/2 is important if the game is to be repeated. It ensures that individuals are better off cooperating with each other than they would be by taking turns defecting on each other.
  • 28. Structure of the Game - Cont’d
    • Iterative PD vs. Single PD
      • Single instance games of PD have a “rational” decision. Always defect, since defecting is a dominating strategy. However, with iterative PD always defecting is not optimal since an “irrational” choice of mutual cooperation will cause a net gain for both players. This leads to the “Problem of Suboptimization”
  • 29. Payoff Matrix
  • 30. Good Guys Finish Last
    • In a single encounter, there is no motivation to cooperate.
      • The defecting pays.
      • Cooperating doesn’t.
  • 31. Iterative Prisoner’s Dilemma
  • 32. Tit for Tat (TFT)
    • The action chosen is based on the opponent’s last move.
      • On the first turn, the previous move cannot be known, so always cooperate on the first move.
      • Thereafter, always choose the opponent’s last move as your next move.
  • 33.
    • Key Points of Tit for Tat
      • Nice; it cooperates on the first move.
      • Regulatory; it punishes defection with defection.
      • Forgiving; it continues cooperation after cooperation by the opponent.
      • Clear; it is easy for opponent to guess the next move, so mutual benefit is easier to attain.
  • 34. Tit for Two Tat (TF2T)
    • Same as Tit for Tat, but requires two consecutive defections for a defection to be returned.
      • Cooperate on the first two moves.
      • If the opponent defects twice in a row, choose defection as the next move.
  • 35.
    • Key Points of Tit for Two Tat
      • When defection is the opponent’s first move, this strategy outperforms Tit for Tat
      • Cooperating after the first defection causes the opponent to cooperate also. Thus, in the long run, both players benefit more points.
  • 36. Suspicious Tit for Tat (STFT)
    • Always defect on the first move.
    • Thereafter, replicate opponent’s last move.
    • Key Points of Suspicious Tit for Tat
      • If the opponent’s first move is defection, this strategy outperforms Tit for Tat
      • However, it is generally worse than Tit for Tat.
        • The first move is inconsequential compared to getting stuck in an infinite defection loop.
  • 37. Free Rider (ALLD)
    • Always choose to defect no matter what the opponent’s last turn was.
    • This is a dominant strategy against an opponent that has a tendency to cooperate.
  • 38. Always Cooperate (ALLC)
    • Always choose to cooperate no matter what the opponent’s last turn was.
    • This strategy can be terribly abused by the Free Rider Strategy.
      • Or even a strategy that tends towards defection.
  • 39. Moral Apes?
    • If true altruism is an adaptive strategy (and not just a good idea that humans invented), then we should see evidence for it in our neighbors, i.e, chimps and bonobos.
  • 40. Our Family Tree
  • 41. The Gentle Ape
    • Bonobos are different from other apes in that they are more peaceful. Females hide estrus=no competition for mates. Engage in frequent sexual activities. Females dominate and attempt to keep peace.
    • Strong female alliances formed. They work together to diffuse tension in the group.
  • 42. Aggressive behavior is only one of several ways in which conflicts of interest can be settled. Other possible ways are tolerance (e.g., sharing of resources), or avoidance of confrontation (e.g., by subordinates to dominants).
  • 43. The Gentle Ape
    • Bonobos had no competition for food with gorillas as chimps did– they had access to herbaceous gorilla-food.
    • This allowed them to live in bigger groups in which females could form alliances, and resources were more abundant.
  • 44.
    • Both chimps and bonobos rely on development of coalitions and community acceptance – even chimps will ostracize a violent bully which means they must survive on the edge of other groups territory – definitely will be severely attacked
    • A fundamental difference between chimpanzees and bonobos: chimpanzees “resolve sexual issues with power while (bonobos) resolves power issues with sex”
    Frans De Waal
  • 45. Weaning A weaning compromise has been arrived at between a mother chimpanzee and her 4-year-old son. After repeated nursing conflicts, the son is permitted to suck on a part of the mother's body other than the nipple.
  • 46.
    • Bonobos
    • Female bonobos defend themselves as a group forming coalitions and show front of solidarity
    • Coalitions are based on kinship
    • Gather in large groups of females which erodes male supremacy
    • Females important in changed social order
    • Females tend to control food supplies
    • Males are not subordinate but strategically deferent
    Frans De Waal
  • 47.
    • Bonobos
    • Old females have power over younger females despite younger advantage in strength etc.
    • How? Emotional controls
      • Rejection of overtures
      • Refuse to share food
      • Refuse to be groomed
    • Alpha females are often in power much longer than males (who are rarely over 5 years)
    Frans De Waal
  • 48.
    • Bonobos
    • Male bonobos are alert to opportunities to ascend power positions in social hierarchy
    • Must be patient as upward mobility depends on mothers position
    • Forms partnerships (coalition) to support position usually with brothers or close friends
    • Often inherit power from a powerful mother
    Frans De Waal
  • 49. Reconciliation Other evidence of an evolved moral sense can be seen in what happens after a conflict occurs. The nature of the social relationship determines whether repair attempts will be made, or not.
  • 50.
    • If there is a strong mutual interest in maintenance of the relationship, reconciliation is most likely. Parties negotiate the terms of their relationship by going through cycles of conflict and reconciliation.
  • 51. Kiss to make-up Fig. 2. Chimpanzees typically seal a postconflict reunion, or reconciliation, with a mouth-to-mouth kiss, as here by a female (right) to the dominant male. De Waal, F. B. M. (2000). Primates--a natural heritage of conflict resolution. Science, 289 (5479), 586-590.
  • 52. Most primates show a dramatic increase in body contact between former opponents during post conflict (PC) as compared with matched-control (MC) observations The cumulative percentage of opponent-pairs seeking friendly contact during a 10-min time window after 670 spontaneous aggressive incidents in a zoo group of stumptail macaques
  • 53. Reconciliations allow rhesus monkeys to maintain tight kinship bonds despite frequent intrafamilial squabbles. Shortly after two adult sisters bit each other, they reunite sitting on the left and right of their mother, the alpha female of the troop, each female holding her own infant. The sisters smack their lips while the matriarch loudly grunts.
  • 54. Capuchin fairness study: Brosnan, S., and F. B. M. de Waal. 2003. Monkeys reject unequal pay. Nature 425:297-299.
  • 55. Brosnan performed a lab experiment in which capuchin monkeys are given a small token (a rock) that they can then return to the experimenter in exchange for a food reward. They like cucumbers alright, but grapes are the really preferred reward. Two capuchins were situated side-by-side in visible but not physical contact of each other, both were presented with an exchange opportunity in turn, and the second monkey’s reaction was the focus of the experiment. Separately both individuals had very high rates of successful exchange.
  • 56.
    • Control:
    • monkey A exchanges token for a cucumber, then subject monkey B also exchanges for a cucumber
    • Experiment 1:
    • - monkey A exchanges the token for a wonderful grape, but then subject monkey B is given only a cucumber in exchange
    • Experiment 2:
    • - monkey A gets a wonderful grape for “free” without an exchange, but subject monkey B then has to go through with the exchange for only a cucumber
  • 57. This is suggested to perhaps be a sense of “fairness” or “justice”. Males didn’t seem to care either way, but female subjects tended to refuse the inequality cucumber exchange – they either refused to take the cucumber or they took it and then quickly threw it back at the experimenter. Thus they conclude that capuchin females pay more attention to the value of exchanged goods and services and are willing to sacrifice a small gain when their neighbor gets a greater reward. Is this due to spite?
  • 58. Our evolved morality:
    • Reciprocal altruism
    • Sympathy & Empathy
    • Consolation & Reconciliation
    • Social norms & punishment of violations
    • A sense of “fairness” but also tolerance for inequality for close friends
    Plenty of evidence from chimpanzees and bonobos to humans showing that many of our moral instincts have been around a long time, all primates demonstrate: See: de Waal (1996) Good Natured, and Flack & de Waal. 2000. 'Any animal whatever'