Especially in parts two and three, we have explained the biological justification of why there are two sexes and why this makes sense. In nature, there are different mechanisms of how the sexes are determined (XX / XY, ZW / ZZ, XX / X0, environmental sex determination). In addition to separate sexes, there are so-called hermaphrodites, i.e. those that combine both sexes in one body (e.g. in many flowering plants or snails).
These forms of sexual determination correspond to the normal distribution of living organisms. Of course, there are deviations from the “norm”. Terms such as “normal”, “abnormal”, “untypical” and “deviations” are to be understood in biology as value-neutral terms that do not involve any discrimination. They only say that there are individuals who do not correspond to the majority. This is also true for sex distribution. It often comes either to chromosomal abnormalities or hormonal disorders (e.g., wasted gonads or genitalia). One speaks of intersexuals, a term introduced by the geneticist Richard Goldschmidt (1878-1958). Some people also bring the concept of the “third sex” into the discussion. However, this is insufficient because no new type of germ cell is formed and many intersex people are sterile (KUTSCHERA 2018: 213-219). A study by BLACKLESS et al. (2000), who collected the results from 20 nations, was able to evaluate that one out of 2,000 newborn babies cannot be clearly assigned to a sex. This means that they are very rare. In addition, all intersex types are integrated here, of which there are quite a few forms. We want to introduce them gradually (according to KUTSCHERA 2018, BLUMBERG 2009, GILBERT 2006).