> But it sounds unlikely that a) there really was that single origin cell, and not a few that popped up around the same time (on a geological scale) This is no

> But it sounds unlikely that a) there really was that single origin cell, and not a few that popped up around the same time (on a geological scale) This is not a necessity. It is entirely possible life on earth was formed multiple times, completely independently and our lineage simply out-competed other sort(s) of life; and somehow we lost the evidence of it, or couldn't find it yet. As it's suggested by other comments, it's a well established fact that the life we know of share the same single origin (this organism(s?) is called the "Last universal common ancestor" or LUCA [1]); but that doesn't mean there has been a single sort of life our lineage ever interacted with, it just means our lineage was the only good-enough life for the conditions on earth for most of the geological periods. [1] https://en.wikipedia.org/wiki/Last_universal_common_ancestor https://en.wikipedia.org/wiki/Last_universal_common_ancestor