The physical differences between men and women are apparent in the size of various body parts, the existence of various body parts and how body parts function, explains LiveScience. Most body parts are different between the sexes for reproductive purposes, including breasts; pitch of voice; body hair; skin pigmentation; and fat deposits.
While filled with fat rather than milk, the full appearance of breasts theoretically indicates a woman's ability to feed children, explains LiveScience. Breasts also signal the likelihood that a woman can reproduce, as prepubescent girls do not have breasts and post-menopausal women have drooping and shrunken breasts. Boys and girls develop nipples in utero at an early embryonic stage, before sex determination occurs.
Skeletal structure varies between the sexes, as men typically have a longer head, a more protruding chin, longer legs and a narrow face, states Dr. James Dobson's Family Talk. Boys' teeth often last longer, and their third finger is usually longer than the first, whereas the opposite is true for girls.
Men have larger voice boxes, which gives them deeper voices and protruding cartilage in their necks, according to LiveScience. The pitch of a man's voice correlates with the level of testosterone he has, an indicator of his sexual fitness. Generally attracted to men with deeper voices, women subconsciously seek mates that are more apt to produce offspring.