Vestigial structures are parts of the body that we have evolved to no longer needed. The process of natural selection dictates that we retain traits that continue to serve a purpose while others become dysfunctional or degenerate. Here are five rudimentary body parts.
1. Application
In humans, this organ dates back almost 80 million years and was used by our ancestors to digest tough plants and vegetables. Located in the lower right part of the intestine, the appendix is approximately 3.5 inches long and less than 0.5 inch wide—its shape is reflected in its Latin name “vermiform,” meaning “worm-shaped.”
Although the appendix is considered vestigial in terms of its original usefulness, modern researchers believed to have evolved to play a role in supporting the immune system thanks to its abundance of lymphoid cells. Other scientists believe that we will evolve to the point where the appendix will no longer be part of the human body.
Read more: What is the function of the appendix?
2. Ear muscles
Our ancient ancestors could move their ears — which they did in response to various sounds. This allowed more accurate identification of the source of the sound. Eventually, human ancestors began to walk upright and sight became more important than sound.
More than 30 million years ago, dry-nosed primates evolved; along with their evolution, the size of their ears and muscles decrease. A 2015 study found that rudimentary ear muscles can still be activated by certain intense or exciting sounds. This led the researchers to believe that further study of the rudimentary auditory system could lead to significant insights. These include the potential to develop tests for auditory deficits in infants and to measure emotions in adults.
3. The sinuses
The paranasal sinuses are air pockets in our skull and facial bones. People have four sets from them:
- Frontal: Located above the eyes — near the forehead.
- Ethmoid: Located on each side of the bridge of the nose, near the eyes.
- Sphenoid: Located behind the nose.
- Maxillary: Located below the cheekbones.
The researchers believe that early ancestors relied on the sinuses for a more pronounced sense of smell, which aided in survival. In modern times, apart from humidifying and warming the air we breathe, they do not appear to serve a significant function. However, these open spaces are prone to infection, either through congestion or disease. They seem to have evolved to possibly aid in production nitrogen oxide, which can strengthen the protection of the nasal cavity. But right now there is no definitive need for sinuses and people can live without them.
4. Coccyx
Many primates have tails that help them balance when swinging through trees. However, when apes evolved about 25 million years ago – they did so without tails. This evolution eventually led to humans. Still human embryos develop tails in early pregnancy, although it is absorbed back into the body. The remainder that remains is the coccyx, also called the coccyx.
Although most babies are born without a tail, there are extremely rare cases where a path is available. When this occurs, the treatment is usually surgical removal, mostly for aesthetic purposes. When the tail exists, it can reach 5 inches in length and is composed of connective tissue, blood vessels, and muscle—but no bone or cartilage.
5. Sages
The diet of early humans consisted of solid food such as raw meat, leaves, roots, plants, nuts and bark. Wisdom teeth (or the third set of molars) were once necessary to grind these foods for proper digestion. The discovery of fire, cooking and eventually eating utensils led to the consumption of softer foods.
Softer foods mean the need for sages was eliminated. During the hunter-gatherer lifestyle, human jaws were adapted for stronger, larger teeth and muscles. As humans transitioned to a more modern diet, this led to the development of smaller jaws. Smaller jaws do not accommodate wisdom teeth easily, so they often cause dental problems.
Read more: How did humans evolve?