Chapter 4 Outline

4.1 Genes and Hormones Guide Sex Development

Learning Objectives:

• 4.1.1 Name the sex chromosomes possessed by females and males and explain how this sex difference arises.
• 4.1.2 Name the precursors of the female and male reproductive tracts, describe what happens to them in both sexes, and identify the hormones that control these events.
• 4.1.3 Identify homologous structures in the external genitals of females and males, and the common embryonic structures from which they develop.
• 4.1.4 Describe or sketch how sex hormone levels change from conception to old age in females and males.

Female and male reproductive tracts develop from different precursors

Female and male external genitalia develop from the same precursors

The gonads descend during development

Sex hormone levels change over the lifespan

The brain also differentiates sexually

4.2 Sex Development Is Not Always Binary

• Learning Objectives:
• 4.2.1 Give two examples of disorders of sex development that are caused by atypical complements of sex chromosomes, and name the chromosomal patterns that cause them.
• 4.2.2 Explain how a chromosomally male fetus develops if it carries a mutation that makes it insensitive to androgens.
• 4.2.3 Explain the possible anatomical and psychological effects of congenital adrenal hyperplasia.
• 4.2.4 Explain the sexual development of a chromosomally male individual that lacks the enzyme 5-alpha-reductase.

Unusual sets of chromosomes affect growth and fertility

The gonads or genitals may be sexually ambiguous

Box 4.1: My Life with Androgen Insensitivity Syndrome

Box 4.2: Intersex and Sports

4.3 There Are Sex Differences in Many Mental Traits

• Learning Objectives:
• 4.3.1 Give examples of gender differences in areas other than sexuality.
• 4.3.2 Give examples of gender differences in the area of sexuality.

Gender identity does not always match anatomical sex

Women and men differ in a variety of cognitive and personality traits

There are many differences in sexuality

Many sex differences arise early in life

4.4 Biological Factors Contribute to Sex Differences

• Learning Objectives:
• 4.4.1 Give an example of how evolution has promoted gender differences.
• 4.4.2 Give an example of how sex hormones during development influence gender differences.

Evolutionary forces act differently on females and males

Experiments demonstrate a role for sex hormones

Box 4.3: Gendered Play in Primates

4.5 Life Experiences Mold Sex Roles

• Learning Objectives:
• 4.5.1 Give an example of how socialization promotes gender differences.
• 4.5.2 Discuss the evidence that imitation is important in the development of gender differences.
• 4.5.3 Explain how “sexual scripts” influence gender differences.

Girls and boys are socialized differently

Cognitive developmental models emphasize thought processes

4.6 Transgender People Challenge Society’s Deepest Divide

• Learning Objectives:
• 4.6.1 Compare the life experiences of transgender people in Western and non-Western societies.
• 4.6.2 Compare the life histories of a typical autogynephilic and nonautogynephilic (“classical”) trans woman.
• 4.6.3 Evaluate different strategies for responding to a child who insists they belong to the other sex from their natal sex.
• 4.6.4 Evaluate the controversy about “rapid-onset gender dysphoria.”
• 4.6.5 Explain some of the stresses and risks to which trans people are exposed.

Transgender men and women have existed in many cultures

Many transgender people are “beyond the binary”

Transexual individuals are of more than one kind

Changing sex is a multistage process

Early treatment of gender-dysphoric children is controversial

Trans people struggle for awareness and acceptance

Box 4.4 Rapid-Onset Gender Dysphoria