Science Knows Why ...
1. You get goose bumps. When you feel a chill or see something scary, your body releases a surge of adrenaline. The point is to make your body hair stand up—which helped our animal ancestors stay warm and also made them look larger in the face of predators. Getting those individual hairs to stand at attention requires the teeny skin muscles at the base of each follicle to contract, making your skin look vaguely like a goose’s postplucking—hence, goose bumps.
2. You grow wisdom teeth. Wisdom teeth are actually a third set of molars. They allowed our forebearers to munch on rough food such as roots, nuts, and meat, especially when other teeth fell out (alas, our ancestors had poor oral hygiene). About 35 percent of people never develop wisdom teeth, partly because of an evolutionary shift that means the human jaw is often too small for them. The rest of us start developing them by age ten, though they don’t fully emerge until young adulthood, which is when we (allegedly) acquire full-grown wisdom.
3. Your fingers and toes wrinkle in water. When you’re in the bath, water seeping into your skin makes the upper layers swell. That causes the blood vessels below to constrict, which in turn causes some of the upper layers of skin to collapse. The irregular pattern of swelling and falling skin is what we see as wrinkles on our fingertips and toes