I have no idea what “whinging” is
LMGTFY
Biology isn’t “messy” at all
Keep in mind I work in a bioassay company and read up regularly on advances in endocrinology and differentiations in human development. I'm also not the only one here that reads up on it... I'm probably not even the one on the forums with the best knowledge.
chromosomes still determine the person’s biological sex. I think most of us learned this in 7th grade science.
And something that you learn in... Well, usually college, is that what you learned in 7th grade is a gross oversimplification, unto the point where almost all of it is laughably wrong.
In some ways the chromosomes advise the function of other systems. I say "advise" because it really is just that, a recommendation.
Methylation of genetic regions, autoimmune responses by the gestational parent, genetic predisposition for or against hormonal reception, chimeric cells, even expression frequencies of specific codes in the DNA can all impact what precipitates from those chromosomes.
As a result you can end up with XY folks with functional uteruses and a majority of testicular tissue, who produce both sperms and who carry eggs, but that's not all... Whose children do not appear as theirs even though they clearly gave birth to and produced the eggs of those children.
The tissue of the gonads itself is separate from the formation of brain tissues which define the subtle differences of the brain which primes the organism for growing up with various behaviors and which inform self-image, and this also reflects differentiated function. There are multiple parts of the brain which can form slightly differently, and this is where I expect gender comes from.
I think it is rather cavalier to proclaim a binary when there are such messy shades of grey. People said the same bullshit you did, but about homosexuals, claiming that it was not possible for someone to be born gay, too, that it was a choice rather than an intrinsic quality of the mind.
Finally, this is again separate from any structures in the brain and body which differentiate from
adolescent hormone exposure.
I nor the reader or listener of the news should be confused over “they/them” as in “They shot up the gay club.
No you should not. The context in the title gives singular "shooter", so anyone whom the public education system has not utterly failed should be fine.
If you are confused by this, I recommend doing your very best to surpass a 5th grade reading level.