I guess today is a Sex Day, as I think every post will be on sex and gender. Right now I just want to call your attention to an excellent discussion of sex versus gender published at the end of last year. Had I known of it, it would have been cited in the “sex is a binary” section of the paper Luana and I wrote for The Skeptical Inquirer. Well, here’s my chance to let you know about this paper now.
Perhaps you’ve already had the gamete-based biological definition of “male” and “female” drilled into you on this site, but in case you didn’t, or even if you did but want to read about purported exceptions to this binary, the paper below in BioEssays is essential reading. It’s the paper you want to give to your friends who doubt that there is a sex binary. (It’s accessible to laypeople.)
Click below to read it, or you can find the pdf here.
I’ve written enough about the sex binary that I don’t want to say more, but I do want to give some nice quotes from this paper to give you an idea of its contents. If nothing else, they provide a review of what I and many other biologists think about sex and gender. So here they are, indented (I’ve omitted most of the references, which are given in the original paper.
Biomedical and social scientists are increasingly calling the biological sex into question, arguing that sex is a graded spectrum rather than a binary trait. Leading science journals have been adopting this relativist view, thereby opposing fundamental biological facts. While we fully endorse efforts to create a more inclusive environment for gender-diverse people, this does not require denying biological sex. On the contrary, the rejection of biological sex seems to be based on a lack of knowledge about evolution and it champions species chauvinism, inasmuch as it imposes human identity notions on millions of other species. We argue that the biological definition of the sexes remains central to recognising the diversity of life. Humans with their unique combination of biological sex and gender are different from non-human animals and plants in this respect. Denying the concept of biological sex, for whatever cause, ultimately erodes scientific progress and may open the flood gates to “alternative truths.”
. . . Yet, the attempt of influential science journals to re-define sex is done for a laudable cause: namely, they wish to promote a more inclusive environment for gender-diverse people in academia and beyond. However, there is no need to deny the biological concept of sex to endorse the rights of gender-diverse people, because biological sex and gender are two entirely separate issues. The gist of the problem seems to be that the definitions of sex and gender and their relationship are not generally appreciated, promoting the spread of flawed notions among readers of high-impact journals.
. . . Biological sex is defined as a binary variable in every sexually reproducing plant and animal species. With a few exceptions, all sexually reproducing organisms generate exactly two types of gametes that are distinguished by their difference in size: females, by definition, produce large gametes (eggs) and males, by definition, produce small and usually motile gametes (sperm). This distinct dichotomy in the size of female and male gametes is termed “anisogamy” and refers to a fundamental principle in biology (Figure 1).
. . . .Biological sex reflects two distinct evolutionary strategies to produce offspring: the female strategy is to produce few large gametes and the male strategy is to produce many small (and often motile) gametes. This fundamental definition is valid for all sexually reproducing organisms. Sex-associated genotypes or phenotypes (including sex chromosomes, primary and secondary sexual characteristics and sex hormones), sex roles and sexual differentiation are consequences of the biological sex. Genotypic and phenotypic features, as well as sex roles are often used as operational criteria to define sex, but since these traits differ vastly between sexually reproducing species, they only work for selected species.
This biological definition of the two sexes is, however, not based on an essential “maleness” or “femaleness” of individuals, but it merely refers to two distinct evolutionary strategies that sexually reproducing organisms use to produce offspring. Sexual reproduction does not require the existence of separate male and female individuals, though. While in the majority of animals, female and male gametes are produced by different individuals, they can also be produced by the same individual, either simultaneously or at different times. For instance, many corals, worms, octopuses, snails and almost all flowering plants are simultaneous hermaphrodites, combining the production of male and female gametes and functions in the same individual at the same time. Many fish species, on the other hand, are sequential hermaphrodites, that is, they change their biological sex during their lifetime. Clownfish (Walt Disney’s Nemo), for example, start their reproductive career as males and only the largest individual of a group turns into a female. Some cleaner fish, on the other hand, are initially all females and later the largest individuals convert to males.
. . . Lest we are misread, we fully endorse the endeavor to create a more inclusive environment for women and gender-diverse people. Gender equity is a humanistic matter of course and it will also benefit science, which – for much too long – has been dominated by a male perspective. It appears, however, that the rejection or the disregard of the biological definition of sex by some philosophers, biomedical scientists and influential science journals is founded in a short-sighted perspective that only considers humans (or mammals) and neglects all other species.
. . . A widespread misconception among philosophers, biomedical scientists and gender theorists – and now also among some authors and editors of influential science journals – is that the definition of the biological sex is based on chromosomes, genes, hormones, vulvas, or penises, etc. or that biological sex is a social construct. These notions very much reflect our own anthropocentric view. In fact, femaleness or maleness is not defined by any of these features that can, but do not need to be associated with the biological or gametic sex.
. . . One reason for this misconception of the biological sex lies in biomedical practices, in which mammalian sex chromosomes or sex-associated phenotypes are widely used to define sex . . . It is this definition that is targeted by critics of the fact that there are only two discrete sexes. However, sex chromosomes or sex-associated phenotypes do not qualify to define biological sex, as there are many species that do not have sex chromosomes at all. Whereas in mammals, birds, or butterflies sex chromosomes trigger sexual differentiation, in many other organisms, environmental factors, such as temperature or social regulators, initiate sex determination or sex change. Hence, sex chromosomes or other sex-determining systems cannot generally define sex. Instead, as the philosopher Paul Griffiths pointed out, “they are operational criteria for sex determination underpinned by the gametic definition of sex and valid only for one species or group of species”. Sex chromosomes, temperature gradients or social cues from group members can all be ways of making a sex, but they do not define it.
. . . Especially in biomedicine, many people are simply unaware of how evolutionary biologists define sex as biological sex. Another set of academics are fully aware of what biological sex is, but are blurring it on account of a political will to treat all people fairly. This stance seems to be motivated by a naturalistic fallacy (the mistake of a moral judgment based on natural properties), or an appeal-to-nature argument (proposing that something is good because it is natural)*, thereby overlooking that “being natural” is irrelevant for ethics. If these misconceptions are spread by scientists it may lead directly to people rejecting science in general, which will be most damaging for progress in society. Our main aim here is to draw attention to the dangers of scientific journals ignoring scientific facts, and to clarify the concept of biological sex.
. . . It is clear that the biological definition of the sexes cannot be the basis for defining social genders of people, as forcefully pointed out by the philosopher Paul Griffiths. Likewise, the socio-cultural, and thus anthropocentric, construct of gender cannot be applied to non-human organisms. There is a red line that separates humans with their unique combination of biological sex and gender from non-human animals and plants, which only have two distinct sexes – both of which are either expressed in the same or in different individuals. As much as the concept of biological sex remains central to recognize the diversity of life, it is also crucial for those interested in a profound understanding of the nature of gender in humans. Denying the biological sex, for whatever noble cause, erodes scientific progress. In addition, and probably even worse, by rejecting simple biological facts influential science journals may open the flood gates for “alternative truths.”
In our paper, Luana and I attribute the blurring of biological sex, and the claims that animals in nature don’t have a sex binary, to a reverse appeal to nature: the equally mistaken view that “what we see as good in human society (a sex spectrum) must be also what we see in nature.”