5 Body Parts No One Really Needs Anymore
Most humans have mastered balance by now, so having a tail is no longer necessary.
Almost all mammals develop a tail at some point during their growth cycle, but not all of them still have it by the time they're ready to pop out of momma.
Humans, for example, have some semblance of a tail around five to eight weeks after being conceived, but it simply becomes part of our vertebrae as we continue to develop.
If you really want to see humans with tails, a quick Google search will satisfy your intrigue.