Anthro 1401, University of Utah Evolution of Human Nature Study Guide Alan Rogers October 16, 2007
Chapter 1 First Half of Course In what follows, I will try to indicate important issues in a general way. For example, item 9 asks What evidence supports the view that species change? (observed change in particular species, artificial selection experiments, variation among domestic animals, etc.) The parenthetical comment is a list of hints; it is not the answer. To answer the question, you would need to be familiar with the specific examples discussed in class and in the readings. 1.1 Evidence for Evolution 1. What are varves? Where do they occur? Why are their layers annual? 2. How can tree rings and varves tell us about ancient climates? 3. The Younger Dryas was the last great cold snap of the last glacial period. Use it to assess the accuracy of dates from varves and tree rings. 4. What is the oldest date obtained from tree rings? From varves? 5. If we did no more than count layers, what could we say about the age of the earth? 6. What is a half-life? 7. The half-life of 238 U is 4.46 billion years. If a rock had a million such atoms when it was formed, how many would be left after two half-lives (8.92 billion years)? 8. How old is the earth? 9. What evidence supports the view that species change? (observed change in particular species, artificial selection experiments, variation among domestic animals, etc.) 10. What evidence supports the view that species change into new species? (species produced by polyploid hybridization, ring species) 11. What evidence supports the view that evolution produces larger differences, such as those between major groups of animals and plants? (homologous similarities, tree-like organization of differences among species, agreement among trees, fossils of intermediate forms, order of appearance of major taxa in fossil record) 12. Be familiar with the examples of bad design that were discussed in class and in the readings. (the possibility of choking on food, male urogenital system, retina, recurrent laryngeal nerve) Why does natural selection sometimes lead to bad design? 13. We covered several arguments against evolution by natural selection: (irreducibly) complex characters can t evolve by natural selection 1
selection can t move population beyond original range of variation chimpanzees and typewriters 2nd law of thermodynamics supposed lack of intermediate forms Be familiar with these and with the responses made to them in class and in the readings. 1.2 Evolutionary Theory 14. What is natural selection? Under what circumstances does it produce evolutionary change? 15. The Grants, working with Darwin s finches, have shown natural selection actually taking place. Be able to summarize their evidence. 16. How fast can selection operate? Can substantial change be produced in only a few generations? (There are several ways to answer this question. One of them would involve referring to the Grants data.) 17. Understand the difference between directional and stabilizing selection. Why does the one cause change and the other prevent it? 18. Understand the difference between frequencydependent and frequency-independent selection. One of these always causes adaptation, and the other does so only sometimes. Understand why. 19. When selection acts on social behavior, are fitnesses likely to be frequency-dependent or frequencyindependent? As a consequence, if selection has affected social behavior, should we expect social behavior to be adaptive? 20. What are the characteristics of a typical sociopath? How might sociopathy evolve by natural selection? Would selection be more likely to favor sociopathy when rare or when common? 21. Does human sociopathy have a genetic basis? Be familiar with the evidence summarized in the reading by Harpending and Draper. 22. Group selection is a hypothetical process that (it has been suggested) produces group adaptations, i.e. adaptations for the good of the group. Give an example of a group adaptation and explain why it is a group adaptation rather than an individual adaptation. What is group selection? What objections to the theory have been raised? 23. Evaluate the idea that langur males kill offspring in order to prevent overpopulation (discussed by Trivers). 24. Evaluate the idea that many species regulate their own reproduction in order to prevent overpopulation (discussed by Trivers). 25. Summarize Trivers s argument against group selection. 26. Be familiar with Trivers s discussion of infanticide among langurs. Is it a consequence of individual selection or group selection? 27. What evidence supports the view that specific learning abilities have been shaped by natural selection? (Soapberry bugs, experiments of Garcia and Koelling, navigation in birds, marriage on the Kibbutz) 28. What are norms of reaction, and how are they involved in the evolution of learning? 29. What is sexual selection? What kinds of characters does it favor, and why are they usually exaggerated in males? Be familiar with a few examples of characters thought to be sexually selected, as discussed in class and in the readings. 30. In some species, sexually receptive females are usually mated by several males. In such species, the sperm of different males compete for access to the ovum. What kinds of mating system make this competition important? What evidence supports the view that sperm competition is important in evolution? (testis size, evolution of sperm proteins) What does this evidence imply about the importance of sperm competition in human evolution? 2
31. In some species, sexually selected characters are exaggerated in females. Why? Be familiar with the Wattled Jacana. 32. Sexual selection happens when one sex has the potential to reproduce faster than the other. It operates either through competition among members of the fast sex (usually males) or through the mate preferences of members of the slow sex. (These are often glossed as male-male competition and female choice. ) What kinds of characters evolve by each mechanism? Why should one sex be more choosy than the other? What evidence supports the view that exaggerated male characters evolve by female choice? (widowbird experiment) What is the sexy son hypothesis? 1.2.1 Nepotism 33. Why are genes said to be selfish? Because selection favors those genes that promote the reproduction of their own type. 34. From a Darwinian perspective why is altruism surprising? 35. What do geneticists mean when they refer to a gene (or allele) for altruism? That a carrier of this allele is more likely (other things being equal) to express altruism than is the average member of the population. 36. What is Hamilton s rule? Write out the rule in words or symbols (explain what the symbols mean if you do it that way), then provide one example of kin selection at work. 37. Summarize three examples that seem likely to reflect the action of kin selection. 38. Why does selection favor cooperation among relatives? 39. What is Hamilton s rule? Be able to write out the rule in words or symbols (explain what the symbols mean if you do it that way) and provide an example of kin selection at work. 40. What evidence supports the view that kin selection has shaped behavior in humans and other animals? (alarm calls in Belding s Ground Squirrels, grooming among Japanese macaques, homicide in humans) 1.3 Climate 41. Use the Wikipedia Ice Ages article to answer just one question: How do we know that the earth was much colder, with extensive ice sheets covering polar regions, during much of the Pleistocene? Ignore the rest. 42. To estimate the earth s temperature in the distant past, scientists often rely on isotopes of oxygen. How does this work? 43. The earth became cooler between 5 and 1.5 myr ago. How large was this change? 44. Be familiar with the pattern and the magnitude of temperature change during the past 800kyr. 45. How rapid were these changes? Does it take thousands of years, hundreds of years, or tens of years to go from glacial conditions to warm conditions such as we enjoy today? 46. What does carbon dioxide have to do with climate change? 1.4 Fossil Hominins 47. Be familiar with the events summarized in Table 1.1. 48. How did the morphology of early Homo differ from that of the australopithicines? 49. In the readings and the text, you will come across several references to a juvenile Homo ergaster skeleton found in East Africa. He goes by several names: Nariakotome Boy, Turkana Boy, and KNM- WT 15000. These are all the same fossil. 3
Table 1.1: Summary of human history When What Where 4.5 1 mya Australopithecines Africa Bipedal, chimp-sized brains 2.5 mya First stone tools Africa 1.8 mya Early Homo erectus Africa & Eurasia Larger brains & bodies Smaller teeth & guts 400 40 kya Neandertals Europe 90 kya Anatomically modern humans Africa & Middle East 50 kya Moderns spread Eurasia Blade tools, art 50. Summarize the history of hominin sexual dimorphism in body size over the past 3 myr. How does the dimorphism of modern humans compare? 51. Summarize the history of hominin brain size and body size over the past 3 myr. Did they follow the same trajectory? Can we tell for sure? 52. Several hypotheses have been proposed to explain the increase in hominin brain size over the past 3 million years. Several of these were discussed in class and in the readings: 55. Another way to ask the same question: What other characteristics would you expect to see in a species with an unusually long childhood? List the characteristics and explain why each should be associated with the length of childhood. 56. Summarize the evidence in favor of the view that this suite of characters evolved roughly 1.8 mya. 57. Summarize the evidence against the view that this suite of characters evolved roughly 1.8 mya. Side-effect of selection on body size. Unpredictable food supply. (fruit or meat) Unpredictable climate. Expensive tissue hypothesis. Social brain hypothesis. Be familiar with each hypothesis and with the evidence pro and con. 53. Modern humans have longer childhoods than other apes. What is known about the time at which this long childhood evolved? 54. In class, Rogers evaluated a hypothesis proposing that the following characters are functionally related: large body, large brain, long childhood, high-quality diet. Summarize the logic that underlies this hypothesis. 4