9 useless body parts that humans no longer need
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Humans' appendix, tail bone, and other organs no longer serve a purpose. Our wisdom teeth also became useless after we began eating softer foods.
Some human body parts have become useless over the past few million years.
Useless body parts include the appendix, the tail bone, and the muscle fibers that produce goose bumps.
Take a look at nine body parts that remained in the human body despite having no function for millions of years.
Some human body parts serve no purpose despite once having a specific function among our ancestors.
Several other body parts used to be important for humans' survival, but they have since become useless. Some of them can be removed, and the absence of them does not lower people's quality of life.
Take a look at nine body parts that remained in the human body despite having no function for millions of years.
The appendix may be the most commonly known useless organ.
"As we started switching to a more diverse diet and targeting meat, we didn't need super long and complicated intestinal tracts anymore," Amir told Business Insider.
However, there is increasing evidence that the appendix does store some useful gut bacteria, but it is unclear if "this was always its function for us, or whether this was an old dog learning new tricks," she said.
The palmaris longus muscle runs from the wrist to the elbow. About 10% of humans do not have it.
"It's been a while since it was useful," Amir said.
Now, however, someone's grip strength is the same whether or not they have the muscle. "Natural selection is not a system geared toward perfect efficiency," Amir said.Â
Humans no longer need very powerful jaws because our diets have shifted toward soft foods and cooked grains. Our jaws are also smaller, so we can't all fit in our wisdom teeth properly.
"Given that we eat pretty soft food now, and molars are usually used for grinding, we don’t really need them anymore," Amir said.
Arrector pili are muscle fibers that produce goose bumps when they contract. Our ancestors, who had a lot more body hair, used these fibers to their advantage, but we don't have a use for them anymore.
For animals with thick fur, arrector pili can help provide insulation. The fibers can also make animals look bigger — a porcupine benefits from this phenomenon.
Human embryos develop a tail between five and eight weeks after conception. The tail vanishes by the time humans are born, and the remaining vertebrae merge to form the coccyx, or tailbone.
Tailbones helped our ancestors with mobility and balance, but the tail shrank as humans learned to walk upright. The coccyx now serves no purpose in humans.
"Our ancestors who had mutations that got rid of the tail seemed to fare better, and thus our tails went away over many generations," Amir told Business Insider.
Auricular muscles control the visible part of the ear, but humans have lost the ability to use them. Other mammals use these muscles to detect prey and predators.
Some humans can wiggle their ears, but that's the best we can do.
The pyramidalis muscle, which is located in the lower abdomen, is shaped like a triangle. People have from zero to two of these muscles, but they don't help us.
About 20% of humans do not have any pyramidalis muscles.
Male and female fetuses initially develop the same way, and testosterone triggers the formation of male sex organs later on. Before these hormones kick in, however, nipples have already begun to develop.
While many male mammals could lactate under extreme scenarios, only the Dayak fruit bat, found in Southeast Asia, lactates spontaneously, according to Scientific American.
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The plica semilunaris, or third eyelid, is a fold of tissue found on the inside corner of the eye. It resembles membranes that some animals use to protect their eyes.
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Birds, reptiles, and some mammals can pull these membranes across their eyes to keep them moist and free of debris.
"It's not exactly clear why humans don't have these anymore," Amir said, "but they're actually rare among primates so we must have lost them a long time ago."
This story was originally published in January 2019.
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