Exam II, Review Sheet. Anthro 160

Major points of this section

The fundamental difference between males and females is gamete size and this reflects an asymmetry in initial parental investment. Those differences in initial parental investment are generally augmented when parental investment extends beyond the energy stored in gametes. While actual levels of parental investment among humans in some societies may be high for males and females, the minimum PI necessary (typical of many mammals) differs dramatically between the sexes. These differences generate other selective pressures on males and females. Since each reproductive event is more costly to females, they are more selective about when and with whom to mate. Female reproductive success is determined by access to resource and their ability to successfully rear offspring. In general, male reproductive success is determined by access to mates, leading to selection for traits that increase efficiency in male-male competition and/or increase the likelihood of being chosen by females as mates.

There are two major life history decisions or allocation tradeoffs: 1) Somatic effort vs. Reproductive Effort and 2) within reproductive effort, quantity vs. quality of children. The quantity-quality trade-off is often expressed in terms of a trade-off between mating effort vs. parenting effort, especially for males.

Human life histories have both cross-cultural regularities and yet are very sensitive to the environmental context that affects the costs and benefits of alternative allocations and rates of development.

Males and females experience different costs and benefits associated with alternative allocation decisions, because of their different commitments to parenting effort vs. mating effort. The differences in male and female life histories and allocation decisions depend heavily on features of the environmental context, especially due to factors affecting both the payoffs to mating effort and the payoffs to parental effort. Human males display a mix of mating and parenting effort, affecting both male and female choice and male and female development.

Population size and density are major features of the environmental context in which life histories occur. The world has undergone and is currently undergoing major transformations in population size and growth, which is affecting every aspect of the human life course. Population size and density affects competition for resources and the nature of competition for resources determines the context for development and reproduction

Questions you should be able to answer:

What is the most accepted theory for the evolution of sex?

What is the biological definition that distinguishes males from females?

What are the characteristics of the more investing sex?

What are the characteristics of the less investing sex?

What is the exception that proves the rule about relative parental investment and sexual dimorphism?

What ecological factors favor male parental investiment?

How do sex differences in parental investment affect sexual dimorphism and growth and development?

How does environmental context affect growth and development differently for males and females?

How does food limitation affect growth and development in males and females respectively?

What happens to growth and development when food stops being a limiting factor?

What special features of human growth and parental dependency distinguish us from other primates and how does that affect preparation for lactation?

What are the two kinds of fat that women have?

How do male and female differences in body fat relate to socioeconomic status?

Can you explain the pattern of female fat distribution?

What is the order of stages in pubertal development among girls and boys, respectively?

Why is the ordering different?

Why does sexual dimorphism exist in characters other than primary sex organs?

What are the major themes in the movie N!ai?

How do men and women acquire mates?

Why is male/male competition and risk-taking a critical feature of male reproductive strategies?

What is the implication of being a member of the sex with the greater variance in reproductive success?

What is the residence pattern of most monkey societies? Which sex disperses and why?

Why do males engage in riskier behaviors than females? How does this greater risk manifest itself in the life history of males versus females?

Terms you should be able to identify:

1. anisogamy

2. sexual dimorphism

3. androgen

4. ranked matriline

5. uterine kin

6. matrilocality

7. patrilineality

8. waist-hip ratio

Sample Questions: Multiple Choice

The fundamental difference between the sexes is:

a. the nature of their reproductive organs

b. the size of their gametes

c. there is not consistent difference

d. their competitiveness

e. none of the above

A ranked matriline occurs in monkeys when:

a. resources are dispersed and difficult to defend.

b. resource clumping both favors intergroup competition and competition within groups for access to resources

c. sisters have no conflicts of interest

d. a and b are both true

e. none of the above

Essay:

Discuss male reproductive strategies and their relation to growth and development of men and then discuss female reproductive strategies and their relation to the growth and development of women. What aspects of environmental context are relevant to sexual dimorphism in physical and behavioral traits?