Spare Parts

Some things that evolution left behind in humans:

THIRD EYELIDA common ancestor of birds and mammals may have had a membrane for protecting the eye and sweeping out debris. Humans retain only a tiny fold in the inner corner of the eye.

DARWIN’S POINT A small folded point of skin toward the top of each ear is occasionally found in modern humans. It may be a remnant of a larger shape that helped focus distant sounds.

SUBCLAVIUS MUSCLE This small muscle stretching under the shoulder from the first rib to the collarbone would be useful if humans still walked on all fours. Some people have one, some have none, and a few have two.

PALMARIS MUSCLE This long, narrow muscle runs from the elbow to the wrist and is missing in 11 percent of modern humans. It may once have been important for hanging and climbing. Surgeons harvest it for reconstructive surgery.

MALE NIPPLES Lactiferous ducts form well before testosterone causes sex differentiation in a fetus. Men have mammary tissue that can be stimulated to produce milk.

ERECTOR PILI Bundles of smooth muscle fibers allow animals to puff up their fur for insulation or to intimidate others. Humans retain this ability (goose bumps are the indicator) but have obviously lost most of the fur.

The link above has more.