It's not terribly surprising, intuitively, that a large range of living things feel and remember pain. The seeming clarity or obviousness doesn't mean it's not

It's not terribly surprising, intuitively, that a large range of living things feel and remember pain. The seeming clarity or obviousness doesn't mean it's not worthwhile to study it, test the assumption, prove or disprove, figure out what creatures are subject to it and to what extent, etc. I imagine we could learn a lot trying to explain it.