You may not know it, but you have a third eyelid. Pull open the two more noticeable eyelids and take a look – it’s located right in the corner by the tear duct. The third eyelid is left over from what’s known as a “nictitating membrane”, which is still present in animals like chickens, lizards and sharks.

No doubt we were once hairier. Up until about 3 million years ago, we were covered with hairs. But by the time Homo-erectus arrived, the ability to sweat meant we could shed our wooly ways.

Doctors don’t really know much about sinuses, only that we have a lot of them. Possibilities for their function range from insulating our eyes to changing the pitch and tone of our voice.

Adenoids trap bacteria, but they’re also prone to swelling and infection. Just ask any 7-year-old. Luckily, our adenoids shrink with age and are often removed.

More useful as a game-winning Scrabble word than a part of the anatomy, the coccyx, or tailbone, is several fused vertebrae left over from the olden days when we had tails.

When were hairier (see No. 9), the erector pili made the hairs stand on end when we needed to appear bigger and scarier. Now, it just gives us goose bumps.

Back in the days when we ate mammoth’s meat off the bone and didn’t floss afterward, our teeth tended to fall out. Therefore, when those reserve molars, aka “wisdom teeth,” came in they were welcomed. Nowadays, fluoride and dental plans have just made them a huge pain.

Darwin claimed the appendix was useful for digestion during our early plant-eating years; it’s dwindled down to little since we started eating more digestible foods.