Indeed. Just because a human HAS had a vestigal tail (keep in mind that it's VERY rare, and almost always removed as a birth defect), does not mean that you can automatically claim that your particular Pathfinder Human has a tail. Nor does that mean that the DM must allow it unless he provides you RAW reference to the contrary.
Nor does it mean that tail is of sufficient size and strength to make a tail attack. The closest thing to a human with a tail in Pathfinder is probably a Tiefling, and, guess what? They don't have tail attacks.
Personally, if you took the feats as your level 1 Human feats, I'd allow it as your DM. But without a sufficient backstory or justification, I'd also allow your starting town to kick you out as a "demonic oddity". You have no starting gold or equipment but the clothes on your back. It was confiscated by the town as a mercy tax so your parents wouldn't go to jail. Those merchants that DO choose to sell to you might mark up their goods 10% or more. Certain Clerics and Paladins may refuse to offer you sanctuary or healing services. So on and so forth...