Why some people have a small hole in front of their upper ears

There is a birth defect of the ear that is visible and relatively common around the world.

It is called preauricular sinus which, according to the U.S. National Institutes of Health, or NIH, "generally appears as a tiny skin-lined hole or pit, often just in front of the upper ear where the cartilage of the ear rim meets the face."

The condition can occur on one or both sides and was reportedly first documented in 1864.

A Business Insider video about preauricular sinus points out that evolutionary biologist Neil Shubin suspects "these holes could be evolutionary remnant of fish gills."

While the exact cause is unknown, according to NIH, "Preauricular sinus may occur sporadically during the development of an embryo or it may be inherited."

Though complications are fairly minimal, they can get infected, but this problem can be addressed with antibiotics or surgery.

Business Insider reports that "between .1% and .9% of the European and U.S. population are born with preauricular sinus."