Research shows that humans, among many other creatures, used to have tails, but it has taken more than one evolutionary event to fully get rid of it. The pelvic tailbone may be one of the only clues as to what humans looked like when we had tails.
Human embryos while developing in the womb develop a tail-like structure because the vertebrae is much longer than the body. As the human embryo develops further, this tail like structure becomes unnoticeable and becomes what is known as the coccyx or pelvic tailbone. This is the final segment of the vertebral column and is common in many mammals.
According to a report from Medical Daily, there are some children who are born with "soft tails" which may have developed abnormally as the vertebrae was taking its full form. These small "soft tails" are normally boneless and are only made from muscles and excess skin.
Although this is medically considered as a genetic anomaly, a report from Institute for Creation Research has indicated that this is an undeniable evidence that we may have been linked to ancient and primitive primates. Since significant anatomy between apes and humans are similar, it is highly likely that they may have come from one source and have simultaneously "mutated" out their tails.
As reported by Live Science, it is in the evolutionary history of all animals that most organisms have evolved from sea creatures or ancient fishes. This is the first incident for which humans may have "lost" or evolved out their tails. However, the report from Medical Daily has shown that a tree-dwelling creature known as Dryomomys szalayi, one of the first and primitive primates ever discovered, may be traced genetically to humans and many other primates. These small tree dwellers are well known for their tales that they use for climbing and balancing on tree branches.