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Unformatted text preview: 1 A simple game for the evening • Step 1 . An individual has been given a bag of M&M’s. That person is required to share. However, they get to dictate how much they share. They do so by making an offer to a second person. • Step 2 . The second person can accept or reject the offer. If the offer is accepted, both players get the agreed upon M&M’s. If, however, the second player rejects the offer, then the M&M’s revert to me. EXAM Results Darwin Darwin ’s Dilemma s Dilemma “There is one special difficulty, which at first appeared to me insuperable, and actually fatal to the whole theory [of evolution by natural selection]. “I allude to the neuters or sterile females in insect-communities; for these neuters often differ widely in instinct and in structure from both the males and fertile females, and yet, from being sterile, they cannot propagate their kind.”-On the Origin of Species Add 150 years, and….. Jan. 2009 Altruism (or cooperation) is the sacrifice of a portion of an Altruism (or cooperation) is the sacrifice of a portion of an individual individual ’s reproductive success (or fitness) in order to increase that s reproductive success (or fitness) in order to increase that of another individual of another individual ’s fitness. s fitness. The paradox The paradox : If altruism reduces an individual’s fitness, natural selection should select against the altruistic trait and eventually reduce its representation within a population to zero. Even if a population started with only altruists , it would be vulnerable to cheating from within: • Imagine a single, mutant selfish individual that could exploit the altruistic tendencies of its neighbors • It would gain the benefits of others cooperating, but NOT pay the price (in terms of reducing its own fitness by cooperating itself) Such a mutant would eventually drive the altruistic trait to extinction. What is altruism, and what is the problem? What is altruism, and what is the problem? Examples of altruism that reduces individual fitness • Numerous animals (Vervet monkeys among them) sound alarm calls to warn others about predators, drawing attention to themselves. • Multiple males defending a pride of female lions even though the dominant male may get most all of the mating opportunities. • Acorn woodpeckers helping their parents to raise a nest of young rather than mating on their own. • Ants, termites, bees and other eusocial insects giving up the capacity to reproduce in order to help a queen. • Naked mole rats…. 2 THE EVOLUTION OF COOPERATION: THE EVOLUTION OF COOPERATION: Why help a potential competitor? Why help a potential competitor?...
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- Spring '09
- Darwin, Kin selection, non-descendant kin, sterile castes, ) Grandchildren Great-grandchildren, Descendant Kin