Because the X chromosome, which is the female chromosome, is the default chromosome. Also, the earliest known human ancestor was a woman, so we can guess that men evolved from women, so it's become an irremovable gene. Or something of the sort.
It's Within the first 4 weeks of pregnancy, every person is female. Then after that period of time depending on which sperm cell you got '' x or y '' determines wether you are going to grow a penis and become a boy.
Thats why boys have the line from the balls to the bum if you think about it... it use to be a vagina but they developed whilst they were in the womb. It's so strange tot hink about it like that though. O_O
The answer is that as embryos men and women have similar tissues andbody parts. If anything the embryo follows a 'female template'.That is why nipples are present in both sexes. It is the effect of the genes, the Y chromosome and the hormone testosterone that brings about the changes and masculinises the embryo. Testosterone promotes the growth of the penis and testicles. Because nipples are there before this process begins the nipples stay! Nipples and breast tissue have no function as such except for perhaps protecting the coração and lungs from injury. Male Breasts Can Produce Breast leite and Get Breast Cancer It is possible for men to produce breast milk.