The election of Donald Trump has been accompanied by an aggressive and ideological attempt to redefine gender and sex, as exemplified by Executive Order 14168, “Defending Women from Gender Ideology Extremism and Restoring Biological Truth to the Federal Government”, which was one of the first executive orders he signed on his inauguration day.

A key aspect of this order is an attempt to reassert a binary notion of sex – male or female. Similarly, it launches an extraordinary attack on what it calls “gender ideology”, essentially arguing that masculinity and femininity are directly correlated to its binary classification of sex as male and female only.

For many people this strikes them as “common sense”. However, the biological reality of sex (not only in humans) is far more complex than a binary conception allows, and gender is very much a different matter from sex – and sexuality is a whole other matter altogether. Far from “restoring biological truth“ this order actually flies in the face of reality.

The next few paragraphs go a bit deep into some aspects of biology. I have minimised the use of scientific jargon and, where needed, provided clarity on aspects. I believe it doesn’t place too much demand on readers who have not studied biology beyond high school.

If one defines sex solely on the basis of genitalia, anyone who has seen more than their own genitalia will quickly realise that there is a wide diversity of genital form – they exist on a spectrum. There is effectively a bimodal distribution of genitalia – very clearly two bell curves that one can generally recognise physiologically as ‘male’ (penis) or ‘female’ (vagina), but there is huge variation within those, and also clear examples of intersex genitalia – that which is not clearly one or the other, or even has aspects of both. The same goes for secondary sexual characteristics too. We all know women that have masculine physical features and men that have feminine physical features. Ultimately there is no “ideal” male or female in physical form, only an abstract ideal that we construct in our minds. That is normal – and there is beauty in this diversity.

Similarly, if one defines sex solely on the basis of chromosomes, one encounters difficulties too. While we may teach, at a high school level of biology, that males have one X and one Y chromosome, while females have two X chromosomes, that is actually a very simplified understanding. Anyone studying genetics beyond the high school level is soon confronted by a much more complex genetic picture in humans (and it’s a lot more complicated in some other species – fungi in particular, with one species, Schizophyllum commune, holding the record at 23,000 different sexes).

It is entirely possible for someone to be genotypically XX yet have the “appearance” of being male in terms of phenotype (how the genes – genotype – appear) – that is, without doing a chromosomal test one would never know. This particular case, de la Chapelle syndrome, occurs in approximately one in every 20,000 people, and they have “typical“ body and pubic hair, penis size and erectile function – although they produce no sperm in their ejaculate. Equally, it is entirely possible to be genotypically XY yet have the ”appearance“ of being female, as in Swyer syndrome, which occurs in about one in every 100,000 people – and, while uncommon, such persons can indeed become pregnant and give birth. And these are only two such examples: one in every 500 people have XXY; one in every 1,000 are XXX; one in every 1,000 are XYY; one in every 50,000 are XXXX; one in every 50,000 are XXXY; and one in 2000-5000 people are just X; and this is not an exhaustive list of possible sex genotypes.

There are also people born with XY chromosomes who present as female at birth and only at puberty develop male organs – testes and penis. This is due to an imbalance in testosterone in the womb, with the surge in testosterone during puberty changing the reality of those so born who had been raised as girls up to this point. While found throughout the world, it is particularly “common” in the Dominican Republic, where those born such are known as ‘guevedoce’ – effectively a third gender.

Biology and genetics is far more complex, beautiful and fascinating than simple binary classifications.

And gender and sex are totally different things altogether. Gender is not inherent to sex. Gender is inescapably a social construct – it varies across cultures and over time within cultures. What is considered masculine or feminine in our culture may be considered the opposite in another culture; and it can also vary within a culture depending on class.

And similarly what is considered masculine or feminine in our culture today has been the opposite in the past – and likely in the future. One need only look at medieval paintings to know that historically men wore skirts; and it was only after the Second World War that we (in the West) came to associate the colour blue with masculinity and pink with femininity – it was the opposite before then.

That we can clearly demonstrate the variability of gender over space and time makes it absolutely clear that there is zero inherent correlation between one’s sex and one’s gender – that is, being feminine or masculine isn’t a question of biology, it isn’t a phenotypical expression of our sex chromosomes. What relationship there is is simply how society applies gender to sex, not that gender is a function of sex.

Once we know that we see how absurd it is to expect anyone to be bound by them – that one can be free to express whatever construct of gender you personally feel best fits you, regardless of social expectation. Some may align their gender identity with social expectations based on their sex, while others may not. In truth, most people are a mix (it’s all about a spectrum), adopting some “masculine” traits as well as some “feminine” traits, regardless of their sex.

And that’s all that “cisgender” or “transgender” means really – cis being Latin for “on this side of” and trans being Latin for “on the other side of”. So, a cis gendered male is simply a person that one would generally agree as physiologically male and also identifies with the masculine gender as per their culture’s understanding of masculine. A trans gendered male is simply a person that we would generally agree as being physiologically male but identifies with the feminine gender as per their culture’s social construct of femininity. And vice versa as regards a cis gendered female and a trans gendered female. And these are just “ideals” in the sense that all of us sit somewhere on the gender spectrum of masculinity and femininity. Just as there is no one who is the ideal sex, so is no one the ideal gender.

And sex and gender are distinct from sexual orientation – to what you are attracted to in sexual terms, something I’ll look to address in more detail another time.

The diversity of sex and of gender is not ideology. It is observable fact, biologically, culturally and historically. And it is beautiful. The only “gender ideology extremism” being waged is that which would seek to restrict this diversity into false binaries and is willing to use extreme violence to do so.

• Jonathan Starling is a socialist writer with an MSc in Ecological Economics from the University of Edinburgh and an MSc in Urban and Regional Planning from Heriot-Watt University