In the summer of 2022, a downright absurd dispute broke out at Humboldt University in Berlin. The university had disinvited a biologist doing her doctorate because, among other things, she wanted to lecture on the fact that there are exactly two sexes in humans. In forums, emotions ran high, nerves were on edge and it was suggested that this statement was controversial. Of course it is not.
Every human being (supposedly with the exception of Jesus Christ) has exactly two biological parents. Not three, not four, but not just one parent either. So far, everything is clear. Nevertheless, some people argue that there are more than two biological sexes. How do they arrive at this?
- It is not easy to define man and woman biologically in an absolutely unambiguous way. If one emphasises physiology (externally visible or ultimately also invisible sexual characteristics), it can be pointed out that there are intersexuals who physiologically exhibit characteristics of both sexes and cannot be clearly assigned to one of the two sexes. However, the chromosomes are also not a reliable indication. Thus, people with XY chromosomes are commonly referred to as men, people with XX chromosomes as women, but there are also deviations here. However, many of these deviations do not play a role in this context. For example, there are people with XXY chromosomes (Klinefelter syndrome), but physiologically they are clearly men. It could therefore be defined quite simply here that people with Y chromosomes are men, people without are women. But here too there is an exception: there are people who do not have a Y chromosome (XX), but who are nevertheless physiologically men. But what makes them physiologically develop into men? This is no longer a secret: they have the so-called SRY gene, which is necessary for the development of male sexual characteristics. This gene is actually located on the Y chromosome, but in very rare cases it can "migrate" to an X chromosome: this is exactly what happens in so-called "XX males". Thus, the biological sex of humans can be defined almost without exception: with SRY gene: man, without SRY gene: woman.
- It is also easy to show that intersexuals are not a separate gender, as is often claimed. Intersexual people are born without a clear physiological sex, for example they have a uterus and a penis. Chromosomally (genotypically), however, they can be unambiguously classified in almost all cases, although the gender identity can again deviate from the genotype. But even in these cases, an intersexual person is not, for example, 30 per cent male and 70 per cent female, but there is either the potential to develop small germ cells (physiologically a man) or to have developed large germ cells (physiologically a woman). As far as we know, there is no example of a mixed form in humans where someone has developed both sperm and egg cells at the same time. And even if there were, this would not be a new gender, but a human being who combines both human genders at the same time. In order to be counted as a new, distinct gender, intersexuals would either have to reproduce asexually or have developed an alternative to sperm and eggs that would allow them an alternative form of reproduction. That this is not the case is obvious, which is why intersexuals are not a "third sex". However, it makes political sense to discuss the question of whether there should be an additional option for intersexuals in addition to the division into biological male and biological female, which is increasingly being done today. In many areas, a distinction is now made between "man", "woman" and "diverse".
- Without exception, all humans have X or/and Y chromosomes. These come exclusively from a father and a mother, i.e. from the two biological sexes. This obviously also applies to intersexuals, which is why they do not represent a gender of their own.
- The statement that there are not only two biological sexes implies that there are more than two biological sexes. If one counts intersexuals as a separate gender, there are three, but how one is supposed to clearly define intersexuals as a separate gender remains a mystery. The proponents of the view that there are more than two biological sexes are definitely in debt to provide a biologically impeccable definition that is superior to the one mentioned above and can clearly classify intersexuals as their own sex. In addition, you must explain how this third sex functions, which should fit categorically to the two biological sexes: If a male germ cell fuses with a female germ cell, a new human being is potentially created. What is the function of the alleged third biological sex in reproduction?
- If there are to be more than three biological (!) sexes, these would also have to be clearly defined, whereby clarity, as usual in biology, must allow for a certain degree of selectivity. In this sense, clear would be, for example, the definition XX - woman, XY - man, <1 per cent exceptions that do not fit clearly into this scheme. The fact that the above-mentioned definition via the SRY gene is almost 100 per cent unambiguous is an exception in biology in terms of unambiguity.
- A third sex is quite conceivable - for example, determined by an additional Z chromosome. In this example, three parents would be needed to produce a child: only when the mother (XX) has mated with two partners (each with a Y and a Z chromosome) would a child be produced. Such a scenario would probably be much more complex in nature than presented here and would hardly bring any additional benefit. Without additional benefits, however, it would not prevail in evolutionary terms. However, it is clear that there is no Z chromosome or anything analogous in humans.
- There is a biological-physiological sex ("sex"), a biological-perceived sex ("gender identity") and a social sex ("gender"). Biologically-physiologically, as shown, there are exactly two genders. There are also exactly two possibilities of the biologically-perceived gender: There are biological-physiological men who identify as women and biological-physiological women who identify as men. The fact that people identify themselves neither as men nor as women, but as a third human gender of some kind, is at least not known to us and should be an extremely rare exception, if at all. Especially since it would be completely unclear what is meant by this third human gender (not in the sense of intersexuals) - here, too, a possible third gender would first have to be defined. It is quite different with "gender", the social sex, whose definition is anything but clear. Gender ultimately includes self-attributions, and one can choose from dozens of possibilities as to what applies to one. However, gender has nothing to do with a biological sex, which is why it has no place in the debate about biological sex.
Biologically, there are different ways to distinguish and define gender. Genotypically (chromosomes, SRY gene), phenotypically (sexual characteristics, potential production of sperm or eggs) or also via gender identity. There are exceptions to most of these definitions, but they do not call into question the principle of bisexuality, which is simply necessary for reproduction. Without two biological parents of different sexes, there is no offspring - and this is how gender can also be clearly defined.