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The video submitted here days ago Trans women are not "biologically male" | Riley J. Dennis caught my attention because I'm a biologist (I'm male feminist just to be clear) that worked with evolutionary ecology and currently working with genomics. I'm sorry, this is gonna be a long, loooong post.
I will comment about what Riley said, what the youtube commenters said and add some points about what /u/DanyaRomulus said and /u/slutzombie said, because of the political importance of it, and because people mix mating system (reproduction) with sex (and this is very, very important).
What caught my attention is people (the commenters in the youtube page) (wrongly) appropriating of biological arguments to justify their hate. The most common argument is the XX/XY chromosomes define "sex." Sorry, if you are using knowledge of high school biology, it's very likely that you are using wrong information, since high school books on biology are oversimplistic.
I will comment here the points raised by Riley (which I agree with) and the youtube commenters (which I disagree with):
- Genitals and gonads (by Riley), for the obvious reason that they are visible attributes, should be taken in account. People with varations in these parts are perfectly healthy, and the intersex parts might even be viable. Oddly, people want to put other people with genitals different than theirs inside a category of disease/disability, which doesn't have strong support by the scientific community. Variation is normal. Variation is part of the evolutionary process.
- The objective of individuals is reproduction (by youtube commenters). Organisms have no objective. This is a misconception of evolution that organisms evolve to do something.
- Hormones (by Riley). Yes, hormones are as important as genes. In fact, hormones might even regulate gene expression. People tend to assume that genes are the supreme commanders, but they are not. Together with gene regulation, hormones and epigenetic mechanisms(which include other substances) might cause gene methylation, leading into inability of a gene to be expressed. Hormones are non visible attributes, and they are as important as the visible attributes (genitals and gonads), as they will determine physiological develoment and change how the organism work (including neurological activity). However, there isn't the hormone that determines sex, and using such thing as testosterone test to determine sex is flawed, as there are many hormones that determine physiological development.
- Sex(ual) determination (and mating system) is fixed (by youtube commenters). First, people are mixing sex(ual) determination, which can be the interest in partners and physiological attributes (non visible) that leads to having interest in those partners, and the mating system, which regards the capability to reproduce. And this is important, because people are wrongly making one dependent on the other: our political system only considers mating system and make assumptions based only on that.
- Chromosomes (by Riley). I left this one for last . First, sexual chromossomes can regulate gene expression, one of the mechanisms is transposition (area I'm starting to work with, these days). And this regulation includes in other chromossomes. Now, transposition is, in short, the process of carrying a gene and putting it in another region of the genome, usually near the original region. This is important, because some genes are "surrounded" by regulatory regions. If a gene is carried and put in a region where it will not be regulated as before, that gene will be expressed differently. In other terms, a characteristic that was regulated by a sexual chromossome (X/Y) isn't anymore. Second, there are cases of XX men and XY women, which leads to more cases of ambiguous determination. In these cases, the individual is usually sterile. The chromossomes then leads to difference in the mating characteristic (the gonads) and the sexual (or gender identification) characteristic. And BOTH are biological, reason why I agree with Riley. If we were talking only about mating, then I would agree with the youtube commenters, but both are important.
Now, which of these are more important than the other to determine ones sex/mating I don't dare to say.
Don't take biology ipsis litteris into political arguments. Biology is a turbulent field that changes fast. Biology doesn't mean fair (see social darwinism). Everything depends on context. /u/DanyaRomulus and /u/slutzombie commented about the counterproductivity of the arguments in the political context: how these arguments can be used against the cause, as dismissing sex-based oppression and rights regarding based on "sex".
By /u/DanyaRomulus:To sum up with an example, I think you'd have a hard time telling a transwoman battling testicular cancer that biological sex is just a social construct.
By /u/slutzombie:Also, claiming that sex is fluid/an identity completely dismisses SEX based oppression, which isn't only relevant to gender, but biologically female anatomy- things like abortion and birth control access, which are really big issues for biological women right now and don't need to be dismissed or danced around anymore than they already are.
This can get even more complicated: what if it's a woman (yes, a woman) with testicular cancer (in this case, a woman with AIS)? What if she is trying to access her healthcare service?
I completely agree with /u/DanyaRomulus and /u/slutzombie. What I'm adding here is how dangerous is to use biological arguments, because it's not simple. It's not just "gender identity" and "biological sex". The "biological sex" can even be ramified into attributes that determine reproduction (genitalia/gonads, and can still be blurry), and attributes that have no context with reproduction (non visible attributes as genetics, hormonal production and neurological), but are still biological.
Ask a biologist about the subject if you need help. I would gladly help. I felt like these informations would be useful, not just to weaponize yourselves, but to not accept simplistic biological arguments just because they taught like that on high school.