and P look like they share a history but they don’t. R began as something of a reversed P. The Romans swung this symbol around and the letter then grew a tail (P was achieving its modern form at this time). The classic Roman alphabet showed R with its tail down to the baseline, but in uncial script first raised the tail off the baseline then shortened the tail. Finally the loop was lost, leaving only the tail and the form of our modern miniscule r.
