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During the turn for the century that is 20th biologist Nettie Stevens had been driven to resolve a systematic secret which had perplexed mankind for millennia. The secret had been therefore easy but daunting: Why do males be girls and boys become girls? In her own 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
Because of Stevens’s work — and also the work that built upon it — we now realize that sex is hereditary, and therefore dads’ sperm in particular determine the intercourse of offspring.
However for almost all of history, this concern had been a mystery that is absolute and it also yielded some interesting theories.
Aristotle believed a child’s intercourse had been decided by the human body heat associated with the dad while having sex. “Aristotle counseled senior males to conceive into the summer if they wanted to have male heirs, ” the textbook Developmental Biology describes.
In 19th-century European countries, it had been widely thought that nutrition ended up being the main element to intercourse determinant. Bad nutrition resulted in men, good nourishment to females.
And through the entire hundreds of years, other gonzo theories abounded. Continue reading Nettie Stevens discovered XY intercourse chromosomes. She didn’t get credit because she had two X’s.