Animals have this in common with one another: unlike humans they appear to spend every minute of every hour of every day of their lives being themselves. A tree frog (so far as we can ascertain) doesn't wake up in the morning feeling guilty that it was a bad tree frog the night before, nor does it spend any time wishing it were a wallaby or a crane fly. It just gets on with the business of being a tree frog, a job it does supremely well. We humans, well . . . we are never content, always guilty, and rarely that good at being what nature asked us to be--Homo sapiens.