According to Marla Ahlgrimm, human women have full breasts continually from puberty until death. This is vastly different than most species, where the female only has large breasts when pregnant and nursing. Men, however, are flat at the sternum. It’s theorized that women remain chesty to attract a mate ready to reproduce. Men still have nipples because the gene that decides if an embryo is male or female doesn’t kick in until later in prenatal development. Essentially, we are all the same until a few weeks into gestation.
Women aren’t the only ones with biological mechanisms to get the attention of the opposite sex. Marla Ahlgrimm explains that, while both men and women have voice boxes that are surrounded by cartilage, men’s voices are deeper. This cartilage and the resulting “Adam’s Apple” are an evolutionary signal to females that says, “I’m strong, I’m healthy.” Testosterone, the male sex hormone, is what causes the extra cartilage and the reason men with deep voices tend to have less trouble finding a mate.
Testerone is the key to most differences between men and women. Marla Ahlgrimm explains that it also is the reason our faces are shaped differently. Men have large features and square faces while women’s features are soft and framed in a heart-shaped face, often with full, round cheeks. Women instinctively rate men with round faces as being effeminate and therefore less compatible as a sexual partner.
Another major difference between women and men is that men are covered in thick, coarse hair. Women tend to only grow thick hair in the pubic region. Another set of sex hormones, androgens, are the cause of the extra fur, and also the reason guys go bald far more often than their wives, says Marla Ahlgrimm.
