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 outlived their apparent usefulness, linger simply because there’s no real reason to leave: What good or bad is hair on the little toe—or even the little toe itself?
Nearly a century and a quarter after Darwin’s death, science still can’t offer a full explanation for why one outdated anatomic trait lingers in the gene pool and another goes. Modern genomics research has revealed that our DNA carries broken genes for things that seem as though they might be useful, like odor receptors for a bloodhound’s sense of smell or enzymes that once enabled us to make our own vitamin C. In a few million years, humans may very well have shed a few more odd features. So look now before they’re gone.
PARANASAL SINUSES
