In the change for the century that is 20th biologist Nettie Stevens ended up being driven to resolve a clinical secret which had perplexed mankind for millennia. The secret ended up being therefore simple but daunting: Why do males become girls and boys become girls? Inside her pioneering just work at 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 exactly how embryos become guys or girls
Because of Stevens’s work — while the work that built we now know that sex is hereditary, and that dads’ sperm in particular determine the sex of offspring upon it.
However for nearly all of history, this concern had been a mystery that is absolute also it yielded some interesting theories.
Aristotle believed a child’s intercourse had been decided by your body heat associated with dad while having sex. “Aristotle counseled senior guys to conceive in the summertime when they wanted to have male heirs, ” the textbook Developmental Biology describes.
In 19th-century European countries, it absolutely was commonly thought that nutrition ended up being the answer to intercourse determinant. Bad nutrition resulted in men, good nourishment to females.
And through the entire hundreds of years, other theories that are gonzo. Læs videre Nettie Stevens discovered XY intercourse chromosomes. She don’t get credit because she had two X’s.