We are all mammals, with much the same physical design as other similar animals. How much should this fact should affect our every day behaviour as wo/men is a matter of debate.
What does ‘the science’ tell us?
The issues are really around basic human / mammalian physiology and also psychology / behaviour.
Human physiology is shaped by genetic influences (chromosomes) but is much more complicated than most people realise.
But this isn’t necessarily prescriptive – humans have much more varied behaviours than any other animal. There are however general patterns in regard to eg parental behaviour, for those who decide to go in that direction. (Some other animals also may never reproduce; and eg same sex coupling sometimes occurs in other species.)
And then there are the many psychology group behaviour aspects, eg, groups which are threatened (or see themselves as such) will behave aggressive-defensibly and reinforce their feelings of difference – which is why keeping channels of communication open is both so important and so hard, not least in politics, which is already a polarised context.
Human physiology and genetics
Issues around sex and gender are extraordinarily complex. Not only are there the usual challenges – for any student of the human condition – around the interplay of what was previously called ‘nature vs nurture’, but there are also extremely strongly held feelings and views on all sides about the ‘meanings’ of these terms.
This is no straightforward exercise in human physiology. Genetics, zoology and psychology are all part of the mix, along inevitably with a fair dash of politics. We will take each of these aspects in turn.
All animals have a combination of genes (see the NIH) . As the NIH tells us:
The gene is the basic physical unit of inheritance. Genes are passed from parents to offspring and contain the information needed to specify traits. Genes are arranged, one after another, on structures called chromosomes. A chromosome contains a single, long DNA molecule, only a portion of which corresponds to a single gene. Humans have approximately 20,000 genes arranged on their chromosomes.
Further, as Live Science reports:
Chromosomes consist of a protein and a single molecule of DNA. Chromosomes make us who we are. […] your DNA is divided into 46 ‘chapters’ called chromosomes — 23 from each parent […] The only human cells that do not contain a pair of chromosomes are reproductive cells (gametes). Egg and sperm cells carry just one copy of each chromosome so that when they unite they become a single cell containing a pair of chromosomes.
The actual genetic make up of animals’ bodies is the genotype, the collection of genes which are inherited when the parents’ gametes – the female ovum / egg and the male sperm – join to make the zygote (fertilised cell) which then starts to divide to become the new foetus.
The appearance of any animal, including humans, is the phenotype – observable traits, such as height, eye colour, and blood type – a combination of all the genetic influences along with other factors such as environment and contexts, nutrition and parenting.
Most of these aspects of what makes a person are relatively unremarkable, but the sex (and ‘social’ gender) of any person is a core attribute in a way more fundamental than any other. At its simplest females have two X genes, and males have one X gene and one Y gene. It’s the gamete from the male, either an X or a Y, randomly, which determines an animal’s actual sex – which is either female or male; there are no other sex-determining genes than the X and Y. This is how sex in humans is determined: All somatic (non-reproductive) cells in human females contain two X chromosomes, and all of the somatic cells in human males contain one X and one Y chromosome.
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Beyond such straightforward, indisputable facts there are however many complications and multiple confusions. One of these is the conflation or confusion in some discussions of ‘sex’ and ‘gender’. As the UK Office for National Statistics (ONS) explains:
Sex and gender are different concepts that are often used interchangeably. The UK government refers to sex as being biologically defined, and gender as a social construct that is an internal sense of self, whether an individual sees themselves as a man or a woman, or another gender identity.
As Planned Parenthood tell us:
…. biological or assigned sex is about biology, anatomy, and chromosomes. Gender is society’s set of expectations, standards, and characteristics about how men and women are supposed to act [….] Some people feel neither male nor female. These people may choose labels such as “genderqueer,” “gender variant,” or “gender fluid.” Your feelings about your gender identity begin as early as age 2 or 3. […] Other people feel that their assigned sex is of the other gender from their gender identity (eg, assigned sex is female, but gender identity is male). These people are called transgender or trans.
Recent large research studies have shown that that there are some genetic connections between different gender or sexual preferences, but none of the genetic influences so far identified is a clear predictor or indicator of how a person defines her or himself in regard to sexuality or gender.
There is no ‘gay gene’, and there are only two sexes. This is important because it clarifies a strongly contested matter: there is, we now know, no third sex, or greater multiples thereof. But both genetic and, even more-so, socio-cultural, studies show that gender – a phenotype (as above) – is more variable than the basic genetics / genotype XX or XY sex.
No-one need have their experience of gender dismissed because there are only two biological sexes. Sex refers to genes, not to what we observe and what we experience, which are sexuality and gender, the outcomes of many different aspects of our bodies and lives.
Nonetheless, it is unlikely that genetics has no part in determining a person’s gender or sexual preferences. Researchers have reported some genetic traits which are associated with some same-sex preference, but none of the genes that they identified could be used alone to predict sexuality. In the words of the author. ‘Nearly half a million genomes reveal five DNA markers associated with sexual behaviour — but none with the power to predict the sexuality of an individual.’
Whatever transpires for any given individual, chromosomes are only X or Y in some variation. There are instances of XXY and other more complex combinations, but all are the result of errors that occur in cell division when the egg or sperm is formed, or occasionally during cell division after fertilization. Any foetus with only a single Y chromosome cannot survive (and abnormal combinations of chromosomes are also likely factors in some early miscarriages).
Human reproduction is dependent just on X and Y chromosomes and these are the basis of all human life. There are only two basic sexes – but there are several different ‘social’ modes of sexual and gender preference, which may present differently in different times and in different places.
Fundamentally, then, there are only X and Y chromosomes – but on the basis of these established scientific facts we can also understand why some people have complex ‘intersex’ genetic make-ups.
Nonetheless, terminology remains an issue. In one study ‘intersex’ was the most preferred term among focus group participants, at some 37%; but only 7% of young people and parents interviewed preferred this term. An alternative, ‘disorders of sex development’ (DSD), was preferred by just less than 20% of focus group participants but by none of the young people or parents interviewed. Larger surveys have also shown that no umbrella or medical terms are uniformly preferred among people categorized under those umbrella terms, or their family members.
[Read and discuss more about Nature vs nurture and Psychology.]
That’s really informative. I studied Geography in the School of Biological Studies at Sussex University and so my knowledge of biology is not particularly comprehensive and it’s certainly very rusty (it was a long time ago!). I do like reading around the science though and here are a couple of short articles I came across which I found interesting
Zach Elliott in Evolutionary Biology April 2021 on What are sexes
Andy Lewis in The Quackometer writes a rebuttal to an article in The Skeptic Magazine 2021
Here’s another relevant post from an evolutionary biologist ~ Sex Is Not a Spectrum
QUOTE: As more and more people refer to themselves as trans, nonbinary, and gender-non-conforming, there’s been a push to reconstrue the notion that males and females exist as real biological entities as obsolete. Instead, some argue, we have only varying degrees of “male-ness” and “female-ness.” And so the very idea of segregating any space or sports using binary sex categories is seen as illegitimate, since, if no definitive line can be drawn, who’s to say a purported “male” isn’t really female? Many even go so far as to claim that we should let people decide for themselves what sex they are, as though this were a matter of personal choice…..