Nettie Stevens discovered XY intercourse chromosomes. She don’t get credit because she had two X’s.

Nettie Stevens discovered XY intercourse chromosomes. She don’t get credit because she had two X’s.

In the turn associated with the 20th century, biologist Nettie Stevens had been driven to fix a medical secret which had perplexed mankind for millennia. The secret had been therefore easy but daunting: Why do men be boys and girls become girls? In her own pioneering just work at Bryn Mawr College, Stevens — whoever birthday celebration is today, July 2 — found the intercourse chromosomes that produce the real difference.

Before Stevens, we were utterly clueless regarding how embryos become guys or girls

By way of Stevens’s work — and also the work that built upon it — we now understand that sex is hereditary, and that dads’ sperm in particular determine the sex of offspring.

However for almost all of history, this concern had been a mystery that is absolute also it yielded some interesting theories.

Aristotle believed a child’s intercourse ended up being dependant on your body temperature of this dad during intercourse. “Aristotle counseled elderly guys to conceive in the summertime when they desired 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 latin mail order brides answer to intercourse determinant. Poor nutrition resulted in men, good nourishment to females.

And through the hundreds of years, other theories that are gonzo.

The 18th-century anatomist that is french Procope-Couteau (the writer regarding the Art of Having males) thought that testicles and ovaries had been either man or woman.

Procope-Couteau “suggested the way that is best to regulate a child’s intercourse is always to eliminate the testes or ovary related to the undesirable intercourse; though a less extreme mean for girls is always to lie from the proper part, and let gravity perform some rest, ” according to The development of Intercourse Determination, a guide by biologists Leo W. […]