Can someone explain why, if life emerges as 'easily' as is mooted by Cronin, it doesn't keep emerging on Earth over and over again. It's been habitable for billions of years, but the accepted theory is that all life on earth has a common ancestor. I suppose the argument could be that there have been numerous genesis events, but only one lineage has survived. Bit again given the idea that life emerged so quickly, the implication is that it will have kept on emerging and there would be some evidence of that...