Why do cats purr?

You ask: Why cat purr?

Caveman be honest — science tribe still argue on this one. But here what most of them think. Cat brain send a steady beat-signal to little muscles in the throat, near the voice box. Those muscles squeeze and open fast — about twenty-five to a hundred-fifty times every single second — both when cat breathe in and breathe out. Air pass the flapping, and a low hum come out: the purr. Strange thing — cat not only purr when happy. Cat purr when hurt, scared, even close to death. So many think purr also calm the cat itself, and the gentle shaking may even help heal bone and body. Cave wisdom: purr not just cat-smile — it a throat-drum cat beat to soothe self, happy or hurting.