Comment Language (Score 1) 481
Its of course not a perfect measure, but the ability to communicate would probably be the easiest guidepost as to what we should/shouldn't eat. Language of some sort is required for a society/culture to develop and without society/culture creatures often act on a purely instinctual level. I don't think we have any concrete evidence of a non-human species on Earth having a language, the closest possibilities would be certain cetaceans. I am sure there are other guideposts (personality, intelligence, problem solving, etc) but communication should be the easiest to recognize.