Dexx writes:
Still, i cant help but think that 3 billion years is an awefully long time. Perhaps another species rose to the height of hunter-gatherers with stone tools and was then wiped out in an extinction event. We may never know.
Keep in mind thought that for the vast majority of those 3 billion years, life was simple and single celled. Multicellular, more complex creatures didn't appear until somewhere around the Cambrian, which was some 550 million years ago. A great bit shorter than the 3 billion you're proposing.