Understanding Asexuality

The above brief discussion of the natural history of asexual and sexual reproduction only indirectly relates to the main subject of this book: asexual humans. The type of reproduction of a species—sexual or asexual—is somewhat different from the phenomenon of asexual beings, including human beings, within an exclusively sexually reproducing species. There is also a distinction between sexuality and the capacity for reproduction. For example, the vast majority of asexual people can still reproduce sexually (i.e., are still part of the sexually reproducing species of humans), even if they are not interested in the sexual mechanisms of it. Finally, in modern humans, sexuality is often divorced from reproduction, so asexuality is (partially) a different phenomenon than asexual reproduction.

More to the main point of this book, then, are there examples of asexual animals within a normally sexually reproducing species? There are. For example, a chorus line of sexual variability exists in farm and lab animals, even though they are often bred—and sometimes genetically altered—to be nearly identical food-producing or lab-friendly machines. As in humans, you can find some that are studs or sexual dynamos. You can also find some having “homosexual” tendencies, in that they prefer sexual relations with the same sex; for example, males not only affiliating with other males but also actively preferring to mount other males rather than females. You can also find animals that have no sexual interest whatsoever in other animals. This pattern of sexual variation among animals is often most clearly observed in males, as it is sometimes harder to determine female sexual tendencies, in part because they, relative to males, are less likely to initiate mating, often having a more subtle sexual response associated with receptivity (see chapter 6 on gender).

Male rodents raised in experimental labs (e.g., mice, gerbils, guinea pigs) often demonstrate wide sexual variability, with behaviors ranging from hypersexual to asexual. These extremes are often called “studs” and “duds,” respectively. Such variability in rodents may have parallels to human sexual variability, including asexuality. Yet there are a number of unknowns. First, some non-mating males may have sexual attraction to other males, and so a lack of mating may not mean asexuality. A second, related unknown is that the conclusions rely on the behavior of the animals, and this is an imperfect measure of underlying sexual attractions, particularly if we are using it as a model of human sexual attractions (see also chapter 2). Third, researchers are unclear as to what factor(s), biological or otherwise, underlie the stud/dud difference. One biological explanation is variations in circulating testosterone, as this hormone is related to sex drive in both animals and humans. However, some animal experiments, including early ones on guinea pigs, indicate that variations in adult-level circulating hormones are probably not the main cause of the difference between duds and studs, because these animals, after being castrated and then readministered a constant level of testosterone, still showed the same behavioral differences (Grunt & Young, 1952; Adkins-Reagan, 2005). Another possibility is that there are differences in certain brain cell structures laid down before birth—called receptors—that make some animals more or less sensitive to testosterone exposure in adulthood. A related possibility is that prenatal hormones organize certain sites of the brain into groupings of cells (nuclei) with specialized functions. This difference in how brain cells are organized/structured prior to birth has implications for human sexual orientation, as a leading biological theory of human sexual orientation proposes that similar mechanisms underlie human variations in sexual attraction. Thus, from a sexual orientation perspective, these “dud” animals may have an asexual orientation because of prenatal factors organizing the brain in a certain way, just as variations in human sexual attractions, including perhaps asexuality, may be affected by such prenatal influences.