I'm not a biologist, but I'd be surprised that genetic reproduction would be as stable 3 billion years ago than now. I would not be surprised that monocellular

I'm not a biologist, but I'd be surprised that genetic reproduction would be as stable 3 billion years ago than now. I would not be surprised that monocellular beings, which don't need DNA replication to survive, had a more defective cloning system, thus more subject to whichever DNA replication bug. Plus, life took about 1 billion years to emerge. This is huge. The solar system took about the same time to form. Also, life may be extremely slow to appear, but once it's there, progression is quicker. Since the beginning of phanerozoic eon (and Cambrian explosion), a geologic period (Pleistocene, Jurassic, Cambrian...) only lasts a few tens of millions years. I find it very plausible that at the beginning of Cambrian era, a critical step in evolution was reached, allowing a better and faster evolution.