APPENDIX: This narrow, muscular tube attached to the large intestine served as a special area to digest cellulose when the human diet consisted more of plant matter than animal protein. It also produces some white blood cells. Annually, more than 300,000 Americans have an appendectomy.

BODY HAIR: Brows help keep sweat from the eyes, and male facial hair may play a role in sexual selection, but apparently most of the hair left on the human body serves no function.

THIRTEENTH RIB: Our closest cousins, chimpanzees and gorillas, have an extra set of ribs. Most of us have 12, but 8 percent of adults have the extras.

MALE UTERUS: A remnant of an undeveloped female reproductive organ hangs off the male prostate gland.

FIFTH TOE: Lesser apes use all their toes for grasping or clinging to branches. Humans need mainly the big toe for balance while walking upright, the other four are for holding when you slam them on a coffee table at night!