Our sex is identical to our gender, written in our genes, can be clearly attributed and does not change during our life. This is what many people say. The woman on one side, the man on the other – you are either a princess or a knight, without anything between the two. And you There is certainly no word to say in the matter. Your sex is what you were born with. Period.
US President Donald Trump believes that. During its inauguration in January 2025, Trump said it would be American government policy “that there are only two sexes, men and women.”
And In a television debate, two weeks before General elections of Germany February 23, 2025, curator Chancellor candidate Friedrich Merz said He rose to Trump’s side in the gender debate.
“This is a decision I can understand,” said Merz.
People who support the concept of “only two sexes” often underline biology as a basis for their point of view that there is only man and woman, immutable and without anything between the two.
However, the broad scientific consensus now seems different: Sex is a spectrumsay some scientists. You can stick to the image that man and woman are at the opposite ends, but a lot of things happen between the two.
Genetics: clearly ambiguous
XX chromosomes = female chromosomes, male. This is how sex is trained, we learn at school. In people with XX chromosomes, a vagina, a uterus and ovaries are normally formed in the uterus. In XY, the penis and the testicles are formed.
Obviously, sex chromosomes are important, but it is not as simple.
For example, there are people whose physical features are women, but they wear “male” sex chromosomes in their cells, and vice versa.
A gene located on the short arm of the Y chromosome, called SRY, determines (with other players) if testicles will form or not in an embryo. If, for example, this gene is not read due to a mutation or remains silent, so to speak, no testicle will develop despite the XY chromosomes.
On the other hand, the testicles can grow in people with XX chromosomes if the gene jumps towards the X chromosome (probably during cell division) and is read.
So, how sensitive is it to determine sex after birth, as does mainly for the moment, only on the basis of external visible sexual characteristics?
Nothing is set in stone
The natural variations of sex chromosomes are numerous and varied. This can also have an effect on visible sexual characteristics, the genitals. Here too, there are several gradations between the fully formed penis and the external visible part of the clitoris.
Individuals who cannot clearly be attributed to one of the binary sexes refer to themselves as intersex or inter *. The United Nations estimate that 1.7% of the world’s population belongs to this group. The number is comparable to that of red hair in the world.
Since 2018, newborns like this can be recorded as “various” in Germany. Other countries, such as Australia, Bangladesh and India, also recognize a third sex.
Sex can also change during a lifetime – or more precisely the gonadic sexual identity can. Chinese researchers discovered it in a Mouse study.
The genes responsible for this change are DMRT1 and FOXL2, which normally balance the development of ovaries and testicles in a sort of Yin-And-Yang relationship. When there has been a change in these genes, the gonadic sex phenotype could even change in adult animals.
The changing symphony of hormones
Testosterone: male hormone! Estrogens and progesterone: female hormones! This is what they teach you at school, but again, it is not so simple.
Men and women as well as individuals in gender division have all these sex hormones in their bodies. Average progesterone and estradiol (the most powerful natural estrogen levels) differ barely between the sexes.
If we seek binarity in hormones, we must rather distinguish between “pregnant” and “not pregnant”, according to a Examine the study on recognized sexual characteristics by American psychologists. Indeed, only pregnant women are far from the ordinary in terms of estradiol and progesterone compared to all the other people.
In children, there is no significant difference in sex hormones. It is only in puberty that testosterone levels in particular increase, so that men have an average testosterone than women.
However, according to recent results, this difference was also overestimated for a long time due to a research failure, because testosterone has not been studied as stereotypical only in men and estrogens only in women.
Today, targeted research is carried out on hormonal overlap between the sexes. It has also been discovered that hormone levels depend to a remarkable external factors and are not, as supposed previously, purely genetically predetermined.
Pregnant fathers, for example, have less testosterone during the period of pregnancy of their partner. So -called feminine hormones Estradiol and progesterone, on the other hand, are produced more when individuals compete for domination – a behavior that is stereotypical considered to be male.
What sex is your brain?
There are differences between the brain of men and women. The men’s brain is larger on average. Individual brain regions also differ in average size, the density of connections and the type and number of receivers.
However, again, researchers cannot identify the male or female brain. Each brain is quite unique and rather resembles a mosaic with different “male” and “female” parts.
At least, this is how researchers from the University Tel Aviv described in a study. A quarter in half of the 1,400 brains studied showed this sex patchwork. Things are therefore also complicated in the head.
This also applies to the brain of trans people, which are studied more targeted. Regarding what individual brain regions look like, trans people are sometimes closer to their perceived sex and sometimes closer to their assigned sex.
It is sure to say that there is no pure binarity of the characteristics of sex. All the so-called “biological” arguments in this sense do not comply with the current state of science.
Sex and sex are such complex and versatile problems as humans (and mice and other animals) that carry them.
This article was initially published in German on March 31, 2021 and was updated on February 10, 2025 with the developments of the televised debate before the German elections.