Nothing would bring us to an expectation that we should remember our births. And, like a shocking accidental death, our end will only be recalled by its witness-- specifically the lizard people. But we can speculate when human memory begins, by trying to find the oldest memory anyone can come up with, and comparing that to other old memories and voting on which one is oldest.
Right now, it seems like "hiring aliens to build the pyramids" and "saving the human race from a flood with a single vessel" are the top two recollections our scientists can retrieve, through Tantric past-life meditation. We've voted, and decided the flood came first. Otherwise the pyramids would have been larger, to withstand T-rex attacks.