During the change associated with century that is 20th biologist Nettie Stevens ended up being driven to fix a clinical secret which had perplexed mankind for millennia. The secret ended up being therefore simple but daunting: Why do men be girls and boys become girls? Inside her pioneering work on Bryn Mawr university, Stevens — whoever birthday celebration is today, July 2 — found the intercourse chromosomes that produce the real difference.
Before Stevens, we had been utterly clueless on how embryos become men or girls
By way of Stevens’s work — as well as the work that built we now know that sex is hereditary, and that dads’ sperm in particular determine the sex of offspring upon it. Continue reading