Testosterone Rex

1. Challenging the "Testosterone Rex" Narrative

Testosterone Rex is extinct. It misrepresents our past, present, and future; it misdirects scientific research; and it reinforces an unequal status quo.

The book's central argument. Cordelia Fine's Testosterone Rex dismantles the pervasive and seemingly unshakeable story that links sex inequalities to inherent biological differences between men and women, particularly focusing on the role of testosterone. The book argues that this narrative, which weaves together claims about evolution, brains, hormones, and behavior, is fundamentally flawed and unsupported by contemporary scientific understanding.

Undermining the narrative. Fine challenges the "Testosterone Rex" view by scrutinizing the dynamics of sexual selection, the effects of sex on the brain and behavior, the relationship between testosterone and behavior, and the connection between our evolutionary past and our possible futures. She demonstrates that rejecting this view doesn't require denying evolution, difference, or biology, but rather taking them into account more accurately.

Moving beyond outdated assumptions. The book aims to transform how we think about the prospects for social change by dismantling the assumption that biological sex differences dictate societal roles and inequalities. It encourages a shift towards a more nuanced understanding of the complex interplay between biology and social construction.

2. Reassessing Bateman's Principles: Beyond Cheap Sperm

Up until very recently, the unquestioned assumptions underlying the study of sexual selection have been that eggs are expensive while sperm are unlimited and cheap, that males should therefore be promiscuous while females should be very choosy and should mate with only the one best male, and that there should be greater reproductive variance among males (as compared to females) because it is males that compete for females and mate with more than one female.

The foundation of the T-Rex view. The traditional understanding of sexual selection, heavily influenced by Bateman's principles, posits that males compete for access to females due to the lower cost of sperm production compared to the higher cost of egg production. This paradigm suggests that males are inherently promiscuous, while females are coy and selective.

Challenging the paradigm. Fine presents evidence that contradicts Bateman's principles, including the re-examination of Bateman's original data, which showed that female reproductive success also increased with multiple mates in some experimental series. Contemporary research has identified numerous species where female promiscuity leads to greater reproductive success, challenging the notion that it is solely a male domain.

Diversity in sex roles. The book highlights the incredible diversity of sex roles across the animal kingdom, demonstrating that biological sex, defined by gamete size, does not rigidly determine mating arrangements or parental care. This variability undermines the idea of a universal template for how genetic and hormonal components of sex affect brain and behavior.

3. Human Sexuality: More Than Just Reproduction

If you’re a human, sexuality is far more than for reproduction; that is what evolution has done for human nature.

Beyond the biological imperative. Fine argues that human sexuality is not solely driven by the biological imperative to reproduce, but also serves other functions, such as facilitating bonding and reducing interpersonal tensions. This perspective challenges the narrow view of sexual selection that focuses solely on bringing together reproductive potentials.

The human dimension. The book emphasizes the uniquely human dimension of sexuality, highlighting the role of culture, social norms, and individual identities in shaping sexual behavior. It critiques the tendency to strip away these human traits in an attempt to understand sexuality from a purely biological perspective.

The long, slow sexual revolution. Fine introduces the idea of a "long, slow sexual revolution," emphasizing that human sexual expression has long been broader than just getting gametes together successfully. This perspective acknowledges the historical and cultural shifts that have influenced our understanding and experience of sexuality.

4. Beyond Binary: The Mosaic Brain

Human brains cannot be categorized into two distinct classes: male brain/female brain.

Challenging the "male brain" vs. "female brain" concept. Fine presents evidence that undermines the notion of distinct male and female brains, arguing that brains are instead comprised of unique "mosaics" of features, some more common in females compared to males, and some more common in males compared to females. This challenges the assumption that sex creates discrete neural circuits restricted to mating.

The influence of environment. The book highlights the interactive nature of brain development, in which multiple factors, including genetics, hormones, environment, and epigenetic influences, all play a role. Environmental factors, such as prenatal stress and rearing conditions, can interact with sex to affect brain development in complex and non-uniform ways.

Sex differences in the brain. While acknowledging that sex differences in the brain do exist, Fine emphasizes that these differences do not necessarily translate into differences in behavior. She points out that the functions of many neural sex differences are mysterious, and that some may even serve to counteract other differences.

5. Deconstructing Risk-Taking as a Masculine Trait

If you risk a life you don’t value, have you taken a risk?

Challenging the assumption. Fine challenges the assumption that risk-taking is an inherently masculine trait, arguing that it is not a one-dimensional personality trait but rather a domain-specific behavior influenced by individual perceptions of risks and benefits. This undermines the idea that men are naturally more inclined to take risks due to evolutionary pressures.

Subjectivity of risk. The book emphasizes the subjective nature of risk perception, highlighting that what one person considers risky, another may not. This subjectivity is influenced by factors such as knowledge, familiarity, and cultural norms, which can vary between the sexes.

Social identities and risk. Fine explores how social identities, such as gender and race, can influence risk perception. She discusses the "white male effect," in which white males in the United States tend to perceive lower risks compared to other groups, potentially due to their privileged social position.

6. Testosterone: Mediator, Not Master

Social events regulate gonadal events.

Challenging the hormonal essence of masculinity. Fine challenges the notion of testosterone as the potent hormonal essence of masculinity, arguing that it is neither the king nor the kingmaker, but rather a mediator that responds to social contexts and experiences. This undermines the idea that testosterone directly causes competitive, risk-taking behavior in men.

Testosterone and social behavior. The book presents evidence that testosterone levels are influenced by social factors, such as status and competition, rather than solely determining them. This suggests that social events can regulate gonadal events, rather than the other way around.

The complexity of the hormonal system. Fine emphasizes the complexity of the hormonal system, highlighting that the amount of testosterone circulating in the bloodstream is just one factor among many that influence behavior. Other factors, such as hormone receptors, conversion to estrogen, and individual sensitivity, also play a role.

7. The Myth of the Lehman Sisters: Dismantling Financial Stereotypes

If the various workplace and non-workplace gaps could be distilled down to a single word, that word would not be “discrimination” but “testosterone.”

Challenging the "Lehman Sisters" hypothesis. Fine critiques the idea that the global financial crisis could have been averted if Lehman Brothers had been run by women, arguing that this hypothesis relies on flawed assumptions about sex differences in risk aversion and testosterone levels. She points out that there is little empirical support for the notion that women are inherently more risk-averse in business contexts.

The role of confirmation bias. The book highlights the role of confirmation bias in perpetuating stereotypes about sex differences in financial risk-taking. Researchers may be more likely to emphasize findings that confirm these stereotypes, while downplaying or ignoring contradictory evidence.

The importance of social context. Fine emphasizes the importance of considering social context when analyzing sex differences in financial decision-making. She argues that factors such as gender norms, societal expectations, and access to opportunities can all influence risk-taking behavior.

8. The Power of Social Construction: Shaping Gendered Behavior

The belief is all but universal that men and women as contrasting groups display characteristic sex differences in their behavior, and that these differences are so deep seated and pervasive as to lend distinctive character to the entire personality.

The influence of gender socialization. Fine emphasizes the role of gender socialization in shaping behavior, arguing that societal norms and expectations can have a profound impact on how individuals perceive themselves and others. This challenges the idea that sex differences are solely determined by biology.

The developmental system. The book highlights the importance of the developmental system, which includes the ecological and social legacies that individuals inherit along with their genes. This system shapes how genetic and hormonal components of sex play out to affect brain and behavior.

Challenging essentialist thinking. Fine critiques essentialist thinking, which assumes that sex differences are fixed, immutable, and ordained by nature. She argues that this type of thinking can reinforce stereotypes and limit opportunities for individuals to develop their full potential.

9. Toward a More Balanced Society: Beyond Biological Determinism

It's time to stop blaming Testosterone Rex, because that king is dead.

The need for social change. Fine argues that achieving a more balanced society requires addressing the social and cultural factors that contribute to sex inequalities, rather than relying on biological determinism. This involves challenging stereotypes, promoting equal opportunities, and creating a more inclusive environment for individuals of all sexes and genders.

Rearranging the developmental system. The book emphasizes the importance of rearranging the developmental system to create a more equitable society. This involves addressing the social structures, values, norms, expectations, schemas, and beliefs that perpetuate gender inequalities.

A call to action. Fine encourages readers to challenge the status quo and work towards a more just and equitable society. She emphasizes that even seemingly minor actions, such as questioning gendered toy marketing, can contribute to meaningful change.

Last updated: March 10, 2025