Male nipples have been a source of comedy and intrigue over the years as more and more people come to realize that they really don’t serve any functional purpose.
Men have nipples simply because they could have been females in the early stages of development.
In the first two months in the womb, both men and women develop the same way. If a Y chromosome is present, the fetus will start producing testosterone, and subsequently male reproductive organs.
But nipples have been left in the male genome simply because having them isn’t a bad thing or a good thing. They just are.
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.