Studyguide 3 (Challenges of and Mating)

Sexual selection

See “ notes” for review (in the section on lecture slides)

1. What is sexual selection? What causes it?

2. Darwin identified two types of sexual selection. What are they? Give some examples of traits likely to evolve from each type of sexual selection.

3. Many , especially male birds, have extravagantly showy plumage. Andersson’s classic study on widowbirds (lecture) suggests that their long tails evolved through sexually selection. Which of the two types of sexual selection (see previous question) is probably responsible?

4. Peahens are similar—is their preference for peacocks with showy trains adaptive? Why? (film “Why Sex”)

5. What is the relationship between (polygyny, , polyandry), , and variance in reproductive success?

6. The cross-cultural data shown in class gave the percentage of cultures practicing polygyny, monogamy, and polyandry. Which is most common? Which is least common?

Women’s long-term mating strategies

1. Women are usually more choosy about mates than men. Why?

2. Women prefer partners with good economic potential. Why? How robust is this general- ization? What related traits are attractive to women? Understand both the evolutionary explanation and the “structural powerlessness hypothesis” (129), and why the text thinks that the latter is not supported by the evidence.

3. Remember that the great disparities in wealth seen in societies today are an “evolutionary novelty” not found in hunter-gatherers.

4. Why do females find physical strength and athletic prowess attractive? Note the argument by Smuts, discussed on pp 120-1, which she has also applied to people.

5. Why is low “fluctuating asymmetry” thought to be an indicator of good physical condition? Which women think symmetrical men look and smell sexy?

6. Women in Victor Johnson’s experiments (film) preferred different male faces when choosing a date rather than a long-term mate, and when choosing in different phases of their menstrual cycle. How did their preferences differ? Why might this make evolutionary sense?

7. Is love an evolutionary novelty? (text)

1 8. In lecture (also in the text), we discussed indicators of genetic quality that have been shown to affect women’s mate preferences, including MHC diversity and low fluctuating asymmetry, both of which are indicators of genes associated with health (review the evidence). Whether or not indicators of masculinity indicate health is controversial (text and lecture). Review. 9. Do women find men more attractive if the men are interacting positively with children (text)? What do we know about women’s ability to assess a man’s interest in children (from lecture)? Does an interest in infants make men more attractive as a long-term or a short-term mate? (lecture). 10. Is evidence from women’s mating and marriage behavior consistent with their stated prefer- ences? (text,132). 11. The answer to the question “Do women like very masculine-looking men (evidence of high testosterone)” is “it depends”. What does it depend on? (text/film/lecture discussed repro- ductive status, interest in short vs long-term mates, and population differences). Understand the reasons why preferences might be expected to vary (see the last 2 slides on the lecture on women’s long-term mating preferences). 12. When reviewing the material on mate preferences, remember that although most of the attention in ev psych has been on areas that differ among men and women (resources, beauty, fidelity, etc) these are not usually the most important criteria for either men or women. The first slides in the lectures for female and male mating patterns make this clear. 13. Does the distinction between butch and femme lesbians have any basis in psychological and/or physiological reality? (see box 4.1, text).

Men’s long-term mating strategies

1. What traits do men prefer in a long-term mate? What things signal those traits? 2. What is reproductive value? What does it have to do with the sex differences in preferred age of a mate? 3. What facial features do men find beautiful in a woman? Why? Are these preferences found cross-culturally? What is the evolutionary explanation for these preferences? 4. At what age do people begin to distinguish attractive from unattractive faces? (Lemley, also text 149) 5. What is the adaptive advantage of having (and preferring, if you are a male looking at a potential mate) a low waist-to-hip ratio? 6. Among the Kipsigis, an E. African agro-pastoral group, men must give their wife’s family a brideprice before they can marry. The ethnographer used the amount of priceprice as a measure of women’s attractiveness. Which Kipsigis women cost more to marry? 7. Although there is a lot of cross-cultural variation in the trait, men in most societies value chastity in a mate more than women do. There is also more societal tolerance for adultery by men than by women. What is the evolutionary basis for this sexual double standard?

2 8. How does seeing pictures of attractive women affect a man’s view of his own relationship? Is it adaptive? (163). Media exposure is a lot like refined sugar – a modern novelty that turns an evolved into something harmful.

9. Testosterone facilitates competition among males and rises in anticipation of it. How is testosterone in men related to marital status and fatherhood? How did it differ between the Hadza (foragers) and the Datoga (pastoralists)? What does this indicate about the difference in male strategies in these two populations?

10. There are many evolutionary explanations that have been proposed to explain homosexual orientation in men, and no consensus about any of them. The most intriguing, in my opinion, is what Buss refers to as the “female fertility hypothesis”. Take a look at it (box 5.1).

11. Averaging pictures of faces usually makes the face more attractive. But exaggerating facial features associated with estrogen (fertility cues) are also seen as more attractive in female faces. Can these both be true? Review the evidence and the disagreement between Perrett and Langlois (discussed in the Lemley article).

Small, “Love with the proper stranger”

There are genetic costs to , and this article reviews evidence that both mice and people avoid mating with individuals who are genetically similar. What are the MHC genes and why are they relevant to this? What is the evidence bearing on MHC and mate preferences? (review both Ober’s and Wedekind’s studies).

Short-term sexual strategies and Polygyny

1. Men, like most mammalian males, benefit reproductively from multiple matings, and their minds and bodies show for it. Review the evidence pp 177ff. (including sperm competition, attitudes, choosiness, closing-time phenomenon, sexual fantasies, behavior). The table 6.1 is a good summary of the evidence.

2. There are trade-offs between paternal investment and seeking additional matings. Under what circumstances would it make adaptive sense for males to invest more in offspring? How does the operational sex ratio affect sex and mating patterns? (text and lecture)

3. Why, and under what circumstances might short-term matings be adaptive for females? (text and lecture).

4. One reason why females might solicit extra mates is to get resources and investment. This (like most of this section) is not limited to humans. Why do female dunnocks (birds discussed in class) solicit extra-pair copulations (EPCs) from beta males, and how do we know?

5. The Bari are a society with beliefs of “partible paternity”. What is that? Does having a secondary male benefit a Bari woman?

3 6. How do women’s mate preferences differ for long vs. short-term mates? What does this suggest about the reasons for engaging in short-term (or extra-pair) mating?

7. Can a short-term strategy be perceived by others? p. 196

8. How does father absence shape mating strategies? We’ll talk more about this later.

9. How does the sex ratio affect male and female mating strategies? (p. 198 and more extensively in lecture). The relevant sex ratio here is what is termed the “operational sex ratio” (the number of males wanting to mate divided by the number of females that are ready to mate).

10. Polygynous men typically have greater reproductive success (higher fitness) than monogamous men, but the same is typically not true for women (see the figure of Utah polygynous vs monogamous marriages). Why is this the usual pattern?

11. The Pimbwe (lecture) were an exception to the rule above. What do the data show for the Pimbwe? (from lecture and Angier reading).

12. If variance in male quality or resources is highly variable, it might be advantageous for a woman to marry polygynously. Why, and and under what circumstances? (this is the ’polyg- yny threshold’ argument discussed in class).

13. The Kipsigis women studied by Borgerhoff Mulder (discussed in class) chose men who had the most resources available after division among co-wives, rather than the most resources overall. Why does this suggest polygyny by female choice (polygyny threshold argument) rather than male coercion?

Asante Market Women

Review/Background: Asante are matrilineal, which means that inheritance (and property) is passed down through the female line. If you were Asante, your matrilineage would include your siblings, your mother, your mother’s brother and her other siblings, your mother’s mother, etc. If you are female, your children would also be part of your matrilineage, but if you are male your children would belong to the matrilineage of your wife/their mother. In this society, children do not inherit from their father, therefore, but rather from the men of the matrilineage (e.g., mother’s brother).

1. Marriage ties are usually not strong in matrilineal societies, perhaps because of the low pater- nal investment associated with it. Is this so for Asante? Are a woman’s closest relationships to her children and matrilineal kin, or her husband?

2. Women have a lot of economic independence in this society. Does this give them power in the home, or are they subordinate to their husbands?

3. What do men and women think of polygyny in this society? Are co-wives competitive?

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