The Way of Science

UNIT 4

APPENDICES

APPENDIX #3: Questions of Evolutionary Theory

  1. Imagine a population of humans.
    1. Would a mutation that increased the number of children per birth (and nothing else!) automatically succeed? That is, would an individual with such a mutation automatically have his or her fitness increased?

    2. All other thing being equal (ceteris paribus), who can have more children: a male or a female? Explain.

    3. If one sex can have more offspring than the other, wouldn't the population be better off with a sex-ratio that favored the more prolific sex? Explain why this question is based on poor evolutionary logic.

    4. Suppose we have 1:1 ratio of sexes in this human population. Then suppose that a mutation occurred that allowed an individual to have more of the prolific sex. Wouldn't this new gene automatically spread through the population?

    5. In many human societies, there is a powerful tendency to reject daughters and favor sons. Could there be an evolutionary/genetic basis for this phenomenon? Consider opossums. Healthy and vigorous females somehow (we don't know how) skew their children's sex-ratio at birth to favor sons. Weak and old females reverse that ratio. Clearly, cultural/social bias is not at work here; can you explain how these biased ratios might enhance the mother's fitness?


  2. In many birds, the males are brightly colored and the females are drab. Unfortunately, bright colors make males much more likely to be killed by predators. Propose a hypothesis to explain why drab and camouflaged males do not replace the gaudy ones.

  3. In many species of bees, wasps, and ants, most females are sterile. In bees, most sterile females spend their time helping the queen (their mother) to produce more offspring (i.e., more sisters to the workers). This potential for female sterility is genetic (inherited). How could a gene or set of genes for sterility (zero individual fitness) be so successful? (This phenomenon, of apparently sacrificing individual fitness to enhance the fitness of others, is called altruism.) Here's a hint: Would it ever be worth your while, in terms of your genes, to sacrifice yourself to save a brother (or sister)? How about three sisters (or brothers)?

  4. A major marketing device these days is to add antibiotics to all sorts of kitchen/bathroom/ household products, particularly cleaners ("Keep your home germ-free!"). Feed for animals raised for slaughter (chickens, cows, etc.) usually contains low levels of antibiotics. Are these additions good ideas? Explain.
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