Gabe Mirkin, M.D.
In prehistoric times, goose bumps may have helped
humans frighten their enemies. Now they’re not much use. The
hairs on your body lie close to your skin and have small muscles
attached to them called arectores pilorum. When you feel cold or
are frightened, these muscles pull on the hairs so they stand out
almost perpendicular to your body, causing small bumps to
appear. Hairs trap air between them in the same way that the
fibers in a sweater trap air, helping to keep you warm. The
arectores pilorum muscles also press against the oil glands
located at the base of each hair shaft and squeeze oil onto the
surface of the skin. The oil covers the skin's surface and helps to
keep the skin warm by reducing evaporation of sweat from the
skin's surface.
Many thousands of years ago, people had more body
hair and fewer clothes. Contraction of arectores pilorum muscles
caused hair to stand on end, making a man appear larger than
he was. Today, our greatest adversaries are other people, and
goose bumps may reveal that you are scared. Now most people
hide their goosebumps with clothes.
December 10, 2005