Human Tails
Human embryos have a tail that measures about one-sixth of the size of the embryo itself. As the embryo develops into a fetus, the tail is absorbed by the growing body. The developmental tail is thus a human vestigial structure. Infrequently, a child is born with a "soft tail", which contains no vertebrae, but only blood vessels, muscles, and nerves, although there have been several documented cases of tails containing cartilage or up to five vertebrae.
Humans have a "tail bone" (the coccyx) attached to the pelvis, formed of fused vertebrae, usually four, at the bottom of the vertebral column. It does not protrude externally.
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