12.1 Chapter Objectives
Learning Objectives
In this discussion of Sexual Orientation and the Evolution of Homosexuality, we’ll address the following questions:
- What is “sexual orientation”?
- How widespread are same-sex mating preferences?
- What factors contribute to the development of homosexuality? Is homosexuality innate, being caused by genetic factors? Or is it influenced by environmental variables?
- Why is homosexuality an evolutionary “puzzle?”
- How can we understand the evolution of homosexuality?
- What is homophobia? How pervasive is homophobia in human cultures? How can we understand the widespread occurrence of homophobia?
Our goals are for you to:
- realize that sexual orientation governs many observable natural phenomena, that themselves can be studied scientifically
- understand that homosexuality is widespread in nature—in human and non-human animals
- realize that homosexuality and homophobia may have arisen as a result of natural selection
- appreciate that our understanding of same-sex sexual preferences is part of an emerging field of study, thus, many of the scientific studies we’ll mention are relatively recent and, like all science, subject to revision
By the end of your reading and our in-class discussion, you should be able to meet the following objectives:
- define sexual orientation, heterosexuality, homosexuality, asexuality, bisexuality, and pansexuality
- explain what scientists mean when they say “sexual orientation is not binary”
- defend, using examples, the statement: “homosexuality is widespread in nature”
- explain the difference between proximate and ultimate explanations for homosexuality
- cite evidence for a genetic basis of homosexuality, as well as evidence that homosexuality is environmentally influenced
- explain why some biologists call homosexuality “an evolutionary puzzle”
- explain why many biologists think that homosexuality is an adaptation that has been selected for
- describe a few of the hypotheses for the evolution of homosexuality
- explain how homophobia could be an adaptation (how could homophobia increase an individual’s fitness?
A statement from the authors
In this chapter, we’ll be discussing the possible causes and evolution of a trait that is deeply personal for many people. People who are homosexual (or hold other non-heterosexual identities) have been victims of abuse, hate crimes, eugenic campaigns, among other forms of inhuman treatment for centuries. As of 2023, same-sex sexual acts are still illegal in 64 countries.
We recommend revisiting the discussion of the naturalistic fallacy in Chapter 9 Section 9.13. Briefly, something does not have to be “biologically natural” to be morally or ethically good and worthy of respect. Debates about whether homosexuality is “natural” have been used to justify inhumane practices like the criminalization of homosexuality, promotion of so-called “conversion therapy,” and many other forms of discrimination.
The authors affirm that people’s sexuality, identities, and behavior are valid and worthy of respect and equal rights – regardless of anything that science has to say.
Please reach out if you have any concerns or suggestions that would make this chapter more sensitive and inclusive.
