The answer has to do withhow humans develop in the womb, said Ian Tattersall, apaleoanthropologist atthe American Museum of Natural History in New York City.

美国自然历史博物馆的古人类学家伊恩·塔特索尔认为，答案与人类在子宫内的发育过程有关。

"Basically,males and females are all built from the same genetic blueprint," Tattersall told Live Science."Then, [they] develop in slightly different directions particularly afterwe hit puberty."

他说：“最初男人和女人是由相同的基因蓝图构成的，后来却朝向不同的方向发育，尤其在我们刚处青春期时最为显著。”

During the first severalweeks, male and female embryos follow the same blueprint, which includes the development ofnipples. However, at about six to seven weeks of gestation, a gene on the Y chromosome induceschanges that lead to the development of the testes, the organ that makes and stores sperm and produces testosterone, according to the book.

在胎儿发育的最初几周，男孩和女孩都遵循共同的发育轨迹，包括乳头的发育。然而，在怀孕6-7周时，Y染色体上的一个基因，开始按照基因蓝图，诱导睾丸的发育。这个男性生殖器官，日后会制造储存精子并产生雄性激素。

Afterthe testes