In the first chapter of The Descent of Man, Charles Darwin identified roughly a dozen anatomic traits that he gleefully described as “useless, or nearly useless, and consequently no longer subject to natural selection.” The list included body hair, wisdom teeth, and the coccyx—superfluous features that served as Exhibit A in his argument that humans did not descend from “demigods” but rather from a long line of fur-insulated, plant-chewing creatures that sported tails.
Darwin’s catalog of oddities was far from complete—our bodies are littered with parts we don’t need. Some are vanishing leftovers from our prehominid ancestors, such as muscles useful for walking on all fours or hanging from trees that appear in various atrophied forms. Others are by-products of a natural redundancy inherent in human sexual development, including nipples on men and the tiny vestigial sperm ducts lurking behind the ovaries of women. Then there are curiosities that, having ...
