What scientists really say about biological sex and gender
The biologist Rebecca Helm has written a thread about biological sex and gender over at twitter that deserves more exposure.
โFriendly neighborhood biologist here. I see a lot of people are talking about biological sexes and gender right now. Lots of folks make biological sex seem really simple. Well, since itโs so simple, letโs find the biological roots, shall we? ย Letโs talk about sexโฆ[a thread]
If you know a bit about biology you will probably say that biological sex is caused by chromosomes, XX and youโre female, XY and youโre male. This is โchromosomal sexโ but is it โbiological sexโ? Wellโฆ
Turns out there is only ONE GENE on the Y chromosome that really matters to sex. Itโs called the SRY gene. During human embryonic development the SRY protein turns on male-associated genes. Having an SRY gene makes you โgenetically maleโ. But is this โbiological sexโ?
Sometimes that SRY gene pops off the Y chromosome and over to an X chromosome. Surprise! So now youโve got an X with an SRY and a Y without an SRY. What does this mean?
A Y with no SRY means physically youโre female, chromosomally youโre male (XY) and genetically youโre female (no SRY). An X with an SRY means youโre physically male, chromsomally female (XX) and genetically male (SRY). But biological sex is simple! There must be another answerโฆ
Sex-related genes ultimately turn on hormones in specifics areas on the body, and reception of those hormones by cells throughout the body. Is this the root of โbiological sexโ??
โHormonal maleโ means you produce โnormalโ levels of male-associated ย hormones. Except some percentage of females will have higher levels of โmaleโ hormones than some percentage of males. Ditto ditto โfemaleโ hormones. Andโฆ
โฆif youโre developing, your body may not produce enough hormones for your genetic sex. Leading you to be genetically male or female, chromosomally male or female, hormonally non-binary, and physically non-binary. Well, except cells have something to say about thisโฆ
Maybe cells are the answer to โbiological sexโ?? Right?? ย Cells have receptors that โhearโ the signal from sex hormones. But sometimes those receptors donโt work. Like a mobile phone thatโs on โdo not disturbโ. Call and cell, they will not answer.
It means you may be genetically male or female, chromosomally male or female, hormonally male/female/non-binary, with cells that may or may not hear the male/female/non-binary call, and all this leading to a body that can be male/non-binary/female.
Try out some combinations for yourself. Notice how confusing it gets? Can you point to what the absolute cause of biological sex is? Is it fair to judge people by it?
Of course you could try appealing to the numbers. โMost people are either male or femaleโ you say. Except that as a biologist professor I will tell youโฆ
The reason I donโt have my students look at their own chromosome in class is because people could learn that their chromosomal sex doesnโt match their physical sex, and learning that in the middle of a 10-point assignment is JUST NOT THE TIME.
Biological sex is complicated. Before you discriminate against someone on the basis of โbiological sexโ & identity, ask yourself: have you seen YOUR chromosomes? Do you know the genes of the people you love? The hormones of the people you work with? The state of their cells?
Since the answer will obviously be no, please be kind, respect peopleโs right to tell you who they are, and remember that you donโt have all the answers. Again: biology is complicated. Kindness and respect donโt have to be. [end of thread]โ
The Science Vet talks about biological sex, chromosomes, intersex people and gender identity.
Y does not necessarily equal M: On what intersex people can tell us about gender identity