It turns out the human body has a sort of junk drawer, too.
We have a number of body parts that served an important purpose for our distant ancestors but are essentially useless now, yet continue to take up space.
In fact, these body parts often cause problems for us, from pain to life-threatening infections, leading us to remove them and confirm that yes, we actually don’t need them at all.
And evolution doesn’t stop. A few of these features are already on their way out, with a good chunk of us born without them at all.
1. Appendix
Your appendix is a tiny tube at the end of your large intestine, on the lower right side of your midsection.
That tiny pouch can become infected and inflamed (appendicitis), which causes sudden pain, nausea, constipation, and bloating. If it ruptures, it could spread infection through the body and become life-threatening.
That’s why removal of the entire organ is a common emergency surgery (about 300,000 performed a year in the US). After it’s gone, you can live a completely normal and healthy life without one.
For a long time, scientists assumed it had no function — that it was a vestigial organ, leftover from when our evolutionary ancestors ate mostly plants, thanks to Charles Darwin.
However, in recent years, evidence has emerged showing that the organ contains a large amount of immune cells, helping the body fight germs, as well as holding beneficial bacteria to help digestion run smoothly.
2. Gallbladder
The gallbladder stores and concentrates bile, a digestive fluid that breaks down fats that are made by the liver. It rests right below the liver in the upper right area of the abdomen.
Like the appendix, removing the gallbladder is a common surgery — more than 1.2 million removals are done each year in the US. This might be required when gallstones cause painful blockages, or a patient experiences frequent “gallbladder attacks” of stabbing pain after eating heavy meals. Surgery might be required when the organ is infected, as well.
When the gallbladder is removed, bile flows from the liver to the small intestine without stopping for storage in the gallbladder first. Digestion can continue normally — bile simply just drips steadily into the digestive tract rather than releasing in large bursts.
3. Tonsils
Tonsils function like lymph nodes, filtering germs that enter through the nose or mouth to protect the rest of the body from infection.
The two fleshy masses live in the back of your throat, and can become chronically swollen or infected. Enlarged tonsils can also block the airway during sleep, causing snoring and disrupted sleep.
If this happens, doctors might recommend getting them removed. This is very common, especially in children — more than half a million are performed in the US every year. Without tonsils, people can still fight off infection without problems.
4. Wisdom teeth
Wisdom teeth can come in at the very back of the mouth in young adulthood, around ages 17 to 25.
Because there’s rarely room for them, they can cause issues like getting stuck under the gum, coming up and pushing the existing teeth togther and damaging them, or harboring decay since they’re hard to reach. This can all cause a lot of pain and swelling.
Around 5 million people get their wisdom teeth removed each year, if they come in at all. About 20% of people don’t have them.
Wisdom teeth are likely remnants from our evolutionary ancestors, when we were eating tough, uncooked food that needed more help from a third set of molars. Research even shows our jaws were bigger back then, big enough to accommodate the extra teeth.
5. Palmaris longus, a muscle in the forearm
This muscle runs from your inner forearm to the palm. It’s used whenever you flex your wrist — from typing on a keyboard, opening a jar, writing, and more — but as much as 25% of people were born without one.
To see if you have this muscle, hold your hand flat and face up. Pinch your fingers together, and if a thin tendon rises just below your palm in the middle of your rest, that’s the palmaris longus. (See example pictures here.)
Even stranger, the muscle may appear on one side but not the other, while others might have multiple in one arm.
Researchers believe we evolved this muscle to climb trees and swing from branches. Now that we’re not doing so much of that anymore, researchers have found not having this muscle doesn’t affect our strength at all.
6. Plantaris, a leg muscle
Like the palmaris longus, the plantaris is a small thin muscle, but runs down the back of the lower leg.
You may have heard of “tennis leg,” which is when this muscle tears, often alongside a tear in the larger calf muscle. This causes sharp pain and even a popping sound in the calf.
An estimated 7% to 16% of people will never have that problem since they’re born without one. While most experts have long considered this to be a basically useless muscle, others suggest that its use lies outside strength, helping us with balance, posture and movement.
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