Recently I remembered that Freeman Dyson has this dissenting view on the origin if life. It’s a little hard to follow, but the basic idea is that life preceded DNA/RNA. It started as simple molecules that were able to metabolize, grow and evolve, but not able to replicate themselves efficiently. In other words, life without DNA. If I understand it correctly, this means DNA/RNA would have had to arise separately, perhaps as a virus that then infected the larger molecules and gave rise to modern cells. The most interesting implication, to me, is that this means life arose more than once. So life arising is not as rare an event as we might think. Maybe it happens relatively frequently under a range of conditions, and maybe Earth is not the only place it happens. Maybe it arises frequently, but it rarely gets off the ground. Dyson admits his theory is rejected or ignored by most biologists, but he insists it fits the facts. I was reading this abstract in Trends in Ecology and Evolution, which was a little over my head but reminded me of Dyson’s theory.

Despite recent progress, the origin of the eukaryotic cell remains enigmatic. It is now known that the last eukaryotic common ancestor was complex and that endosymbiosis played a crucial role in eukaryogenesis at least via the acquisition of the alphaproteobacterial ancestor of mitochondria. However, the nature of the mitochondrial host is controversial, although the recent discovery of an archaeal lineage phylogenetically close to eukaryotes reinforces models proposing archaea-derived hosts. We argue that, in addition to improved phylogenomic analyses with more comprehensive taxon sampling to pinpoint the closest prokaryotic relatives of eukaryotes, determining plausible mechanisms and selective forces at the origin of key eukaryotic features, such as the nucleus or the bacterial-like eukaryotic membrane system, is essential to constrain existing models.