Read the following, available in the Reserves section of Shields Library or in my office (Plant Environmental Sciences 1312), by next week. Estimated reading time (in a quiet place without interruptions): 35 minutes, but allow at least an hour so you have time to think about what you read and to answer the questions below.

• "The Tragedy of the Commons." This title is so well-known, it is sometimes quoted (like some Shakespeare quotes) without explicit citation of the original paper. Even after I crossed out some sections that are less relevant to course themes, to save reading time, this paper contains several ideas which (if correct!) have important implications for several different course themes: 1) human population growth, an important factor driving various trends, 2) cooperation among humans (key to successful defense against dark information), and 3) evolution of virulence or benevolence in microbes. You can download a clean copy from the web at http://www.jstor.org/browse under General Science / Science vol.162:p.1243 or many other places on the web (but I've seen versions edited to remove discussion of overpopulation, the author's main topic!).
• "On human population growth." Watch for points relevant to several previous readings.
• "Fertility volatility"
• "Population, economics, environment, and culture: an introduction to human carrying capacity." This article summarizes some key points from Cohen's book, which is one of the more informative and balanced discussion of human population questions. At least read the first page and look at Figure 2 (what are the implications of the "constant fertility" curve? Fig. 1B is also interesting. Read the rest if you like.
• "Legume sanctions and the legume-rhizobia mutualism." Is this the solution to the tragedy of the bacterial commons? Only the first paragraph is assigned.
  
• "Evolutionary progress and levels of selection." Depending on your biology background, parts of this paper may be confusing, but I hope you will understand some of it. Meiosis and syngamy are the key steps in sexual reproduction (e.g., production and union of sperm and egg). Think about tragedies of the commons at each evolutionary stage discussed. A book, "The Major Transitions in Evolution" is a more up-to-date and detailed treatment
• "Evolution of cooperation and conflict in experimental bacterial populations." Experimental data relevant to one of the transitions hypothesized in the previous paper. I am only assigning the first paragraph (in bold type), but read the whole thing if you have time. In this case "cooperation" means spending resources to produce chemicals that help a group of neighboring bacteria to stick together and float rather than sink. This paper also cites some of the most important papers in the scientific literature of cooperation, including the previous one.

1) Hardin quotes Darwin's grandson on ongoing human evolution. How long did C.G. Darwin suggest that the changes that concerned him might take?

2) Sandvik refers to the three factors that determine "a trait's per-generation response to selection" (i.e., the rate of evolution of that trait, i.e., the rate at which its frequency in a population changes over generations). What are those three factors?

3) In the "Fertility volatility" paper, how do differences among groups mentioned compare to changes since 1950?

4) When Cohen says "the facts should immunize you", what kind of replicator is he offering to protect us against?

5) In the paper by Kiers et al., what did defectors fail to do and what happened to them?

6) If the cells within a plant or animal competed against each other, what fundamental "privilege" would they compete for, according to Maynard Smith?

7) In the paper by the Rainey's, what did "defecting genotypes" fail to do?

Questions to think about (to be discussed in class)

• This week's readings discuss two main questions: 1) how worried should we be about human population growth, and 2) does sustained cooperation (among humans or among microbes) require some kind of coercion or sanctions? The size and the density (people per acre) of human population can affect the rate of evolution and dispersal of dangerous microbes. Perceptions that population growth is "out of control" could perhaps lead to risky attempted "solutions." Cooperation among humans is one key to reducing the dangers from rampaging replicators. Various forms of cooperation among microbes may determine whether they are helpful or harmful to humans or crops.
• What do you think are the most important points from Hardin's paper? For each, point, do you think he is: 1) right, 2) wrong, or 3) right in some sense, but misleading, so the information is likely to be misinterpreted or misapplied? Information or insights in the other papers are also relevant to this question.
• If we want microbes to evolve to be beneficial rather than harmful, what conditions would we need to create? We will discuss this topic again with specific reference to human pathogens, after some additional reading.