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.
Some human body parts serve no purpose despite once having a specific function among our ancestors.
The appendix, for example, is not an essential body part (though some research suggests it may act as storage for good bacteria). In some cases, the appendix gets inflamed or ruptures, which requires surgical removal of the organ.
Several other body parts used to be important for humans' survival, but they have since become useless. Some of them can be removed, and their absence does not lower people's quality of life.
Take a look at nine of the most useless body parts.
The appendix may be the most commonly known useless organ.
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 our wisdom teeth properly.
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.
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.
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.
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.
The palmaris longus muscle runs from the wrist to the elbow. About 10% of humans do not have it.
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.
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.