One of the Conservative criticisms of the generally left-leaning March for Science is the refusal of many modern scientists to embrace the so-called fact that “there are only two genders”. The problem with this criticism is that it is not based on fact at all.
While used interchangeably in casual speech, sex and gender are not really the same thing. Sex refers to an organism’s reproductive structures, which are determined by hormones and chromosomes. Gender refers to a role that a human takes in their society, which is often, but not always, determined by sex. While modern Conservatives may prefer a society that has only two genders that are always determined by a person’s sex, not all human societies agree with that (this can be explored at http://www.pbs.org/independentlens/content/two-spirits_map-html/ ). Science generally and anthropology specifically therefore says that “there are as many genders as society says there are.”
The question then moves from “how many genders are there?” to “how many genders should society allow?” and “who is allowed to identify as what gender?”. While Conservatives have made their preferences quite clear on that subject, they have not presented convincing arguments for why society should conform to their preferences. Thus far two arguments have been advanced. The first is the vicious lie that allowing transgender people to use bathrooms designated for the opposite sex puts children or cis-women in danger of sexual assault by trans-people (Brady 2016). The second argument is the fact that it can be confusing to keep track of the seemingly ever-expanding number genders other than masculine/male and feminine/female and the pronouns that people in those genders may prefer.
The idea that transgender people represent a threat to cis-gender people has already been disproven (Brady 2016) so there is no need to engage with it further. The fact that keeping track of people’s gender and pronoun preferences can be confusing, is not a good reason to fail to accommodate them within reason. Our society already accommodates dietary preferences, both religious and otherwise, even if we do not find veganism or the idea that pork is “unclean” ethically or theologically compelling. We have also learned to accept the occasional turban, hijab, or yarmulke in an otherwise “no-hats” workplace. Referring to someone by their preferred gender and pronoun really is not any more difficult.
While most humans belong to one of two sexes, gender is socially variable and there does not seem to be any social disadvantage to multiple genders or people identifying as a gender that does not “match” their sex. As a result, from this scientist’s perspective the answer to “how many genders should society allow?” is “as many as people want to have” and the answer to “who is allowed to identify as what gender?” is “every person can decide for themself”. While not a scientific principle per se, “live and let live” is a highly rational philosophy.
Anonymous. “A Map of Gender Diverse Cultures” PBS http://www.pbs.org/independentlens/content/two-spirits_map-html/ Accessed 24-Apr-2017
Brady, J. 15-May-2016. “When A Transgender Person Uses A Public Bathroom, Who Is At Risk?” NPR. http://www.npr.org/2016/05/15/477954537/when-a-transgender-person-uses-a-public-bathroom-who-is-at-risk Accessed 24-Apr-2017
Gruber, K. 23-Sep-2016. “Five wild lionesses grow a mane and start acting like males”. New Scientist https://www.newscientist.com/article/2106866-five-wild-lionesses-grow-a-mane-and-start-acting-like-males/ Accessed 24-Apr-2017
Marshall, M. 9-Nov-2011. “Zoologger: The only cross-dressing bird of prey”. New Scientist. https://www.newscientist.com/article/dn21138-zoologger-the-only-cross-dressing-bird-of-prey/ Accessed 24-Apr-2017
 Although there are reports of female lions that act like males (Gruber 2016) and male harriers that act like females (Marshall 2011).
 They seem to ignore the fact that not all humans are XX females or XY males.
 This seems like a good time for the singular “they”.