When Will We Evolve Out of Our Useless Appendages?

 

  Never. We’re probably permanently stuck with our pinky toes, tailbone, and just about all our other evolutionary holdovers. Wisdom teeth could eventually go, but significant changes like losing an appendage (teeth included) take millions and millions of years—who knows if humans will even be around that long? What’s more, most of our seemingly useless vestiges are actually helpful.

   

   The coccyx, or tailbone, “is an attachment point of a number of muscles at the pelvis. We need it for upright locomotion. It would be catastrophic if it went away,” says Kenneth Saladin, an anatomist and physiologist at Georgia College and State University. The pinky toe helps us keep our balance and diffuses impact throughout the foot when we run.

   There are only a handful of truly useless parts of our body, but these are hanging on, too. As Saladin puts it, “Since vestiges like the muscles behind our ears have very little impact on reproductive success, there’s no way to select against them.” In other words, the ability to ear-wiggle doesn’t interfere with the ability to have kids.

    The silliest of all vestiges is the male nipple. “Those don’t have a function,” Stearns says, “but they won’t disappear, either.” All embryos, male and female, begin developing according to the female body plan. Only around the sixth week of gestation do the genes on males’ Y chromosomes kick in. “The developmental plan has the two nipples there, so you can’t get rid of them genetically, because that would mess up the breasts of females.” and nobody wants that.