The human body is a marvelous machine, but like many machines that have evolved over time, it contains some leftover parts. According to the Mother Nature Network website, these leftover body parts appear to have lost their original uses:
- Appendix. This tiny pouch in the abdomen near the intestines may have been necessary when early humans survived on a plant-based diet. Today it seems largely superfluous, aside from being an unwanted storage place for bacteria.
- Wisdom teeth. A leftover from when humans’ jaws were larger, the extra molar no longer comfortably fits in most people’s mouths and frequently has to be extracted in early adulthood.
- Jacobsen’s organ. In animals, including reptiles and amphibians, this organ in the nose detectspheromones emitted by potential mates. Although present in the human nose, it appears not to function in modern-day humans.
- Extra eyelid. Birds and reptiles have a nictitating membrane in their eyes that functions as a third eyelid. It’s called the plica semilunaris, and apparently humans have it too, left over from earlier incarnations. It isn’t entirely useless, though; it still helps to drain tears and remove foreign objects from the eye.
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