 What is the probability of being human?
kd5bjo: Your question is ill-formed, and cannot be answered without further information.  In particular, you haven't specified the domain of inquiry.  If you're asking about the probability that a person reading your question is human, the answer is close to 1.  If, on the other hand, you're asking about the probability that a group of protons, neutrons, and electrons form themselves into a human, it is vanishingly small.