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A Brazilian baby boy was born with a 5-inch real human tail. After the ultrasound was negative for any nervous system involvement, the baby was taken to the operating room and had a successful surgery to remove it.
There are approximately 40 cases of real human tails have ever been reported.
Around the fourth week of gestation, most of us start to grow a tail while in the womb, but it usually disappears by the eighth week, eventually morphing into the tailbone, otherwise known as the coccyx.
It is thought our ancestors originally had some form of a tail, but we evolved as a species over time without the need for the organ, so we no longer grow them.