1.0 Introduction

Science is all about knowledge

Science is all about asking questions, generating new knowledge, and asking refined questions on the basis of that knowledge. We can study science through the lens of sex–sex appeal, sexual reproduction, sex and gender, and sexual orientation–as there are many questions regarding the topic that remain unanswered.

Consider the following questions

  • Do animals besides humans have sex for fun? If so, which ones?

The authors of this text have often heard people claim that humans are exceptional in being the only, or one of the very few, animals that have sex for fun. But is this true? And how would anybody know whether other animals are having fun during sex? To look at the question from a different angle: why else would an animal have sex? Are they actually engaged in family planning?

  • Why do young men masturbate so much?

Most people masturbate, but young men between the ages of 12 and 25 take all the prizes for masturbation frequency. While the masturbation question may seem silly (“because it’s fun, of course!”), it’s actually worth asking. Masturbating requires energy, wastes sperm and energy-rich ejaculate, and the associated erections and ejaculate can cause embarrassment in some contexts (e.g. dormitories, buses). We’ll discuss masturbation, in an evolutionary context, in other chapters.

  • Is homosexuality inherited?

The factors that influence sexual attraction are still far from clear. While we’ll look at studies that argue for a genetic basis to at least some forms of same-sex sexual attraction, we’ll discuss studies that consider many non-genetic factors as well. In addition to addressing the question of homosexuality, we’ll encourage you to consider who is asking the questions (for example, why might some individuals feel compelled to seek a genetic basis for homosexuality? Why might others want to refute genetic arguments?), and why.

  • What’s the function, if any, of the female orgasm?

Human female orgasm is a mystery in many respects. It can take many different forms, is not required for conception, and may occur outside of a “typical” sex act. Scientists have attempted to tackle the question of the function of the female orgasm, as well as the issue of whether female orgasm is evolutionarily adaptive (i.e., does it increase an individual’s reproductive success?).

  • Does the HPV vaccine lead to more teenage sex?

The human papillomavirus (HPV) is associated with several deadly cancers, thus many health professionals advocate vaccinating adolescents prior to the onset of sexual activity. However, this recommendation involves parents making a decision that, for some, seems like giving their children “permission” to be sexually active. Thus, there has been some question about whether receiving the vaccine will make an individual more likely to engage in sexual activity, especially at an early age. We’ll discuss this question in the following pages. But first, what do you think?

  Points to Ponder

  • Does the HPV vaccine lead to more teenage sex? What do you think?
  • How would you go about gathering evidence to answer this question?
  • How would you address any of the above questions?

These questions, and limitless others, all lead to a central tenet of this text: SEX, AND SCIENCE, ARE EVERYWHERE. Sex affects human lives along many dimensions—from how we interact as societies, to individual health, to evolutionary success. We’ll use the evolution and biology of sex to address science as a discipline—both a body of knowledge and a way of creating knowledge. By the end of our discussion, you’ll be able to address—if not actually answer—all of the above questions, as well as many others.

Important Note: Sex-positive versus pro-sex

The authors of this text are working from a “sex-positive” viewpoint. By “sex-positive,” we mean that we will not be vilifying consensual sex in any form. We view sex as a natural product of biological forces, expressed in a diversity of presentations, and ideally associated with healthy individuals and societies. This is different from being “pro-sex.” We hope to never make recommendations or express opinions about individual choices related to sexual activity, including your ability to choose abstinence or express asexuality.

Please keep this “sex-positive” viewpoint in mind during your reading, our in-class discussions, and your interactions with peers. You should be able to express your own opinions and be heard, while respecting the opinions of others, but in the end, our class is a “sex-positive” space.



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The Evolution and Biology of Sex Copyright © 2020 by Sehoya Cotner and Deena Wassenberg is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.