Think about what must’ve happened to create this existential niche. It must’ve been observed multiple times that boys who lost their package could hit higher notes later in life.

This almost certainly rules out accidental discovery, as the loss of testes accidentally would not create a statistical correlation.

There was a history of euneuchificaton in the middle east, where slaves where castrated to nullify their sex drive and ability to procreate. In that it must have been noted that if you do it to boys before a certain age it retained their youthful voices.

Can people just not put a knife to others people genitals?