A tiny percentage of the world's population is born with a small hole near the top of their ear, and while it looks like a piercing, the real explanation is much more interesting.
The hole, or pit, is typically situated on the front of the upper ear, where the cartilage meets the face. In the United States, only 0.1 percent of people have it, while nearly 1 percent have it in the United Kingdom. In Asia and parts of Africa, anywhere from 4 to 10 percent of people have it. One study concluded that 5 percent of South Koreans have this ear pit.
This small minority of people suffer from a congenital disorder known as preauricular sinus, which may affect one or both ears.
Discovered by Van Heusinger in 1864, the preauricular sinus usually does not cause any symptoms. However, it can lead to complications if it becomes infected or forms a cyst, and sometimes it is necessary to surgically remove the sinus, according to the Genetic and Rare Diseases Information Center.
IFLScience reports that the condition is caused by the first and second pharyngeal arches, and here is where things get intriguing. These arches emerge during embryonic development and are common to all vertebrates. In mammals they develop into structures within the head and neck, while in fish they evolve into gills.
EvolutionEvidence.org expands on the subject:
Early in development humans (as well as birds, reptiles, amphibians, and, of course, fish) all have these gill like arches. In our ancestors, they developed into gill arches. In us, some of these gills develop into parts of our jaw, inner ear, and throat, such as the hyoid bone (the free floating bone directly above the "Adam's apple" on our neck …). One such example is the preauricular (before the ear) pit, which in essence is a tiny gill slit.
This theory comes from fish paleontologist and evolutionary biologist Neil Shubin, who argues that the preauricular sinus is actually an evolutionary remnant of fish gills, according to IFLScience.
Shubin was featured in a PBS series called "Your Inner Fish," in which he explained why we should look to fish to learn more about ourselves.
"It soon became clear that being a fish paleontologist is a very powerful way to teach human anatomy," Shubin said in the video. "Because often some of the best road maps to our own bodies are seen in other creatures."
Sources: IFLScience, Genetic and Rare Diseases Information Center, EvolutionEvidence.org, PBS / Featured Image: Smooth_O/Wikimedia Commons / Embedded Images: Kiara Sapinoso/Twitter via IFLScience, Caleb Long/Wikimedia Commons