The Two-Sex System: Fact Or Fallacy?

STUDENT CASE STUDY—BAUER

THE TWO-SEX SYSTEM: FACT OR FALLACY?

CASE STUDY FOR AAC&U STIRS PROJECT

Angela Bauer, Professor and Chair of Biology, High Point University, High Point, NC

STUDENT CASE

Introduction

Perhaps no other method of categorization permeates our culture so thoroughly as that of classifying according to sex (biological characteristics we associate with being male or female) and/or gender (social behaviors we associate with being masculine vs. feminine). The desire to categorize in this regard is so compelling, that typically the first words out of a person’s mouth upon hearing about the birth of a child are, “Is it a boy or a girl?” Likewise, the desire to categorize as male vs. female or masculine vs. feminine is far-reaching; names, hairstyles, clothing, bathrooms, athletic events, even shampoos—all are categorized within the context of the binary male/female framework.

Yet is this binary view of sex and gender accurate? Does it reflect what exists within the natural world? Can everyone be placed into one of two “boxes” (male or female) with respect to their sex and gender? And why is the impulse to categorize in this regard so strong? While it is true that at times our culture and media attempt to celebrate the concept of androgyny, most people admit to reacting with discomfort when faced with an individual or situation that defies categorization by the sex/ gender binary. Consider the case of female athlete Caster Semenya, whose sex was investigated following her gold medal win in the 800-meter dash of the 2009 World Championship:

“In August 2009, Caster Semenya, a young South African runner, won the women’s 800-meter race at the Berlin World Championships in Athletics by a margin of 2.45 seconds and immediately found herself at the center of international controversy amid a frenzy of speculation about whether she was ‘really’ a woman (Clarey 2009). The controversy was sparked by complaints from Semenya’s competitors; they pointed not to the large margin of her win, but to what one writer referred to as her ‘breathtakingly butch’ appearance (Levy 2009), remarking, ‘Just look at her’ and ‘These kinds of people should not run with us . . . For me, she is not a woman. She is a man’ (Adams 2009; Levy 2009). Shortly after the media reported these comments, a supposedly misdirected fax notified the press that the IAAF had actually required Semenya to undergo ‘sex testing’ shortly before her Berlin win (Levy 2009). The IAAF had ordered South African authorities to perform the tests after Semenya broke a national junior record at the African championships in Mauritius.

Throughout the testing, Semenya had been under the impression she was undergoing standard doping tests owing to her win (BBC 2009).

In a moment when she might have been celebrating her victory, Semenya endured a cruel and humiliating media spectacle; sports commentators ridiculed her appearance, called her names including ‘hermaphrodite,’ and cried out for her medal and prize money to be returned (Levy 2009; A.D. Smith 2009). Under a typical headline, Time.com trumpeted ‘Could This Women’s World Champ Be a Man?’ (Adams 2009). Semenya was reportedly subjected to a two-hour examination during which doctors put her legs in stirrups and photographed her genitalia (Levy 2009; A.D. Smith 2009). Afterward Semenya sent distraught messages to friends and family (Levy 2009; A.D. Smith 2009). Test results purportedly indicated that Semenya had an intersex condition that left her without a uterus or ovaries and with undescended testes producing androgens at three times the typical level for females (known as hyperandrogenism) (Hurst 2009). [Note that Semenya’s elevated androgen levels did not confer to her any athletic advantage, due to the fact that she lacks androgen receptors to mediate the hormone’s effects.] After these intensely intimate details about Semenya’s body became a topic for public debate and scrutiny, she went into hiding; she reportedly required trauma counseling in the wake of claims that sex tests confirmed she was a ‘hermaphrodite’ (Levy 2009; A. D. Smith 2009).

The IAAF banned her from competitions while it completed its investigation. Eventually, after an 11-month investigation—a process that involved 10 months of negotiation with the IAAF involving legal representatives and a high-profile mediator known for his work on international disputes—the IAAF cleared Semenya for competition and her Berlin victory was allowed to stand (Dewey and LeBoeuf 2010).” [Excerpt taken from Karzakis et al. 2014]

Of note regarding Semenya’s story is the fixation of her fellow athletes, the media, and the public on her androgynous appearance (more so than on any athletic advantage her intersex condition may have conferred; Karzakis et al. 2014). Significant discomfort (in some cases, ridicule) was elicited by her appearance, which didn’t fit neatly within the sex/gender binary. There existed so much discomfort in this regard that Semenya was actually pressured into having significant medical procedures performed to “feminize” her appearance, including surgery to reduce the size of her clitoris. Clitoral reduction surgery is a risky and complicated medical procedure, conducted for the sake of feminizing appearance. Furthermore, the surgery can cause scarring, pain, and numbness in the vulva, resulting in long-term impairment of one’s sexual response (Crouch et al. 2007; Piaggio 2014). In short, it is a surgery that is performed for the benefit of upholding the sex/gender binary, and not for the sexual health of the individual. And yet it is still a surgery that is widely used within the medical community to “treat” intersex individuals like Semenya (Fausto-Sterling 2000; Romao et al. 2012; Piaggio 2014).

In this case study, you will engage in readings and activities that encourage you to consider the validity of society’s two-sex system. In addition to learning about the biologic factors that contribute to sexual phenotype (male, female, intersex), you will examine data sets that illustrate the significant variability in expression of secondary sex characteristics that exists within the natural world. You will consider the role that scientific texts have played in perpetuating the formation of the sex/gender binary. Finally, you will engage in debates with your peers, during which you will formulate arguments that are either in favor of or against the application of binary views and language pertaining to sex and gender on college campuses, particularly when making decisions pertaining to campus housing.

Specific learning objectives for the case study—as well as the activities and assignments included to address each objective—include:

Learning Objective / Related Activities/Assignments
1. To explain the biology of sexual development and the contributions of six key factors—chromosomes, gonads, hormones, external genitalia, internal genitalia, and secondary sex characteristics —to sexual phenotype / Unit One
·  Reading assignment: “The Biology of Sex” (contained in this document)
·  Designing a “Determinants of Sexual Phenotype” flowchart
2. To explain the causes of intersex conditions, their prevalence within the human population, and common approaches used within the medical community to “treat” them / Unit Two
·  Reading assignments:
“Intersex Conditions: Causes, Prevalence, and the Medical Community’s Response” (contained in this document); “What If It’s (Sort of) a Boy and (Sort of) a Girl?,” http://www.nytimes.com/2006/09/24/magazine/24intersexkids.html?pagewanted=all&_r=0/
·  In-class completion of the “Predicting Sexual Phenotype” activity
·  Viewing of “Hermaphrodites Speak,” http://www.youtube.com/watch?v=BwSOngdR7kM/
3. To analyze and interpret data sets illustrating variability in expression of common secondary sex characteristics / Unit Three
·  In-class completion of “Distinct or Overlapping Populations?”
Learning Objectives, cont’d. / Related Activities/Assignments
4. To evaluate the experiences of intersex individuals, in order to identify the challenges they face within the context of society’s two- sex system / Unit Four
·  Reading assignments: “A New Era for Intersex Rights,” http://www.newyorker.com/online/blogs/newsdesk/2013/12/a-new-era-for-intersex-rights.html/; “In Amerika They Call Us Intersex,” http://www.libidomag.com/nakedbrunch/archive/hermaphrodites.html/; “A Girl Named Steve,” http://www.libidomag.com/nakedbrunch/archive/girlsteve.html/; optional Pulitzer Prize-winning novel Middlesex, by Jeffrey Eugenides
·  Unit Four discussion questions
5. To describe how scientific texts have contributed to the perpetuation of the two-sex system / Activities and readings included in Units One to Three
6. To formulate an argument that either defends or argues against application of the two-sex system on college campuses / Unit Five
·  In-class completion of a debate: “The Sex/Gender Continuum and The College Dorm”

Unit One: The Biology of Sex

Suggested Supplemental Readings

·  Fausto-Sterling, A. 2012. Sex/Gender—Biology in a Social World [Chapter Three]. New York: Routledge.

·  Jones, R. E., and K. H. Lopez. 2006. Human Reproductive Biology, 3rd edition [Chapter Five]. San Diego: Academic Press.

Sex is often discussed—particularly in traditional science textbooks—as being a relatively straightforward issue, with clear categories of male and female. Yet a closer examination of sexual phenotype (observable characteristics)—particularly in the case of intersex individuals like Semenya—reveals that the physical expression of sex is much more complex. In reality, sexual phenotype is comprised of six different markers, and none of these is strictly binary. These markers include chromosomes, gonads, hormones, internal genitalia, external genitalia, and secondary sex characteristics. The role of each of these markers in contributing to sexual phenotype is the focus of Unit One of this case study. Of note is the fact that prior to masculinization or feminization of reproductive structures during human development, all embryos—regardless of sexual genotype (genetic makeup of an individual)—possess a neutral phenotype. In other words, the physical structures that initially comprise the reproductive system are identical, and include gonads (indifferent gonads or gonadal ridges) that are neither ovary- or testes-like, a set of internal tubes (the Mullerian ducts and Wolffian ducts) that in no way represent (but have the potential to form) masculine or feminine structures, and a collection of external tissues (including a phallus) that is undifferentiated (in other words, neither penis- nor clitoris-like). These neutral tissues—and the structures that they have the potential to form, depending on chromosomal and hormonal influences —are depicted in Figures 1 and 2 and summarized in Table 1.

Figure 1. Development of Gonads and Internal Reproductive Structures

[OpenStax College - Anatomy & Physiology, Connexions Web site. http://cnx.org/content/col11496/1.6/, Jun 19, 2013]

Figure 2. Development of the External Genitalia*

[Human Physiology, Wikispaces.com, 2011.]

*Note that the perineum is the entire region that surrounds and includes all of the structures pictured above.

Table 1. Potential Contributions of Embryonic Reproductive Structures to Sexual Phenotype

Embryonic Structure / Potential Trigger / Key Factor(s) Influencing Differentiation
gonadal ridges / Genes / If SRY gene is present and Rspo1 is absent/inhibited then, testes form / If Rspo1 is present and SRY gene is absent, then ovaries form
Mullerian Ducts / Anti-Mullerian Factor (AMF) / If AMF and receptors are present, Mullerian ducts degenerate. / If AMF or its receptors are absent, Mullerian ducts differentiate into oviducts, uterus, cervix, and the upper one-third of vagina
Wolffian Ducts / Testosterone / If testosterone and its receptors are present, Wolffian ducts develop into epididymis, vas deferens, and seminal vesicles / If testosterone or its receptors are absent, Wolffian ducts degenerate
genital tubercle,[1] urogenital folds, and labioscrotal swellings / Dihydrotestosterone (DHT, produced by action of 5a-reductase on testosterone) / If DHT and its receptors are present the glans (head) of penis enlarges, the urogenital folds fuse along perineal raphe to form shaft of penis, and the labioscrotal swellings form the scrotum / In the absence of androgens and, possibly, the presence of estrogen, growth of the genital tubercle is limited and becomes the clitoris, urogenital folds become labia minora, and labioscrotal swellings become labia

Six Markers of Sexual Phenotype

Chromosomes

[For a review of chromosomes, DNA, and genes, visit this link: http://www.genome.gov/26524120/.]

While much remains to be discovered regarding the genetic controls of sexual differentiation, two genes in particular seem to play key roles in pushing the process in either a masculine or feminine direction. These two genes are the SRY gene (the “sex determining region on the Y chromosome”) and the R-spondin gene (referred to as Rspo1 and found on chromosome 1). Both play a role in directing the maturation of the neutral gonads (the first step in sexual development). Rspo1 plays a key role in directing the neutral gonads to form ovaries in embryos that have an XX (female) genotype. When the SRY gene is present (in other words, in embryos that have an XY or male genotype), SRY inhibits Rspo1, thereby causing the neutral gonads to form testes.

Recent research indicates that humans can develop testes for gonads even with an XX genotype (in other words, even with no Y chromosome or SRY gene) if they lack Rspo1 activity. In such cases, genetic testing reveals a feminine genotype (XX) in individuals that have a masculinized phenotype.

Gonads and Hormones

Once the aforementioned genes (Rspo1, SRY) orchestrate gonadal differentiation, the mature gonads (ovaries or testes) then produce hormones that direct the differentiation of other reproductive structures (the internal and external genitalia). In XX embryos, the neutral gonads differentiate into ovaries between weeks eight through twelve. It is the estrogen (female sex hormone) produced by these ovaries—as well as estrogen produced first by the mother that causes the internal and external genitalia to feminize (as is described in the next section). In XY embryos (in other words, when SRY is present and inhibits Rspo1 activity), the neutral gonads form testes typically by week eight. These testes then produce two key hormones that play a role in directing the internal and external genitalia to masculinize. These two key hormones are testosterone (an androgen, or male sex hormone) and Anti-Mullerian Factor (AMF; this hormone is also referred to as Mullerian Inhibiting Substance, or MIS).

An important caveat to the success of hormonal activity is the availability of receptors to mediate hormone actions. As Figure 3 illustrates, hormones exert effects on target cells only when they can bind to their receptors (found either on the surface of cells or inside cells). It is the hormone-receptor complex then that is able to alter the activities of a cell/tissue /organ. If an individual lacks the appropriate receptor(s) for a given hormone, that hormone—regardless of how much of it is present—will be unable to exert changes within the body.