testes

In particular, it can lead to a micropenis and undescended testes - which, if you know the British war-time song, had been another rumour flying around about Hitler.

Instead, a subtle form of natural selection within the testes appears to give certain mutations a reproductive advantage, allowing them to become more common during sperm formation.

If a human embryo has XY chromosomes the SRY gene leads to the formation of testes, which then produce hormones including testosterone that lead to male development - and can increase muscle mass and strength.

The masculinity crisis seizing our land saw surprising numbers of Gen Z men break conservative to vote Trump back to office and, before that, a push for testes tanning.

In the brain, sexual differentiation starts before birth and results from a combination of sex chromosomes in brain tissue, sex hormones produced by the testes or ovaries and the environment.