In 1890, the X and Y chromosomes were discovered. It was found that the men who were tested had 46 chromosomes, including an X and a Y, while women who were tested also had 46 chromosomes, including 2 X chromosomes.
So obviously the conclusion was that the Y chromosome defined masculinity.

BlueSky is trying to monetize so let's show them some numbers:

Reskeet this if you refuse to pay for BlueSky+ until trust & safety decides to prioritize marginalized users.

That's $96 / year of lost revenue for each reskeet...