Yesterday we asked when and how life on earth began. We didn't answer that question. We offered a scenario for a proto-life, but also noted that much more would have to happen for that to become cellular life as we generally understand the term. It is possible that life -- considered as something DISTINCT from the proto-life I discussed yesterday, had two origins. There were two paths forward, so to speak, bacteria and archaea. The bacteria developed first. Muh later, the archaea developed and absorbed the bacteria so the later became the energy producing part (the mitochondria) of larger cells. As to the timing? The best guess sets the early RNA replication (proto-life) at about 4 billion years ago. There were complicated cells, leaving a fossil record, by 3.5 billion years ago, so each of the two paths described above had been executed by then. IF any of this is right. Science proceeds by falsification, and this all may be falsif...
The origin of life on earth -- a lasting scientific mystery -- may have a lot to do with alkaline hydrothermal vents. These are geysers - like vents found in the ocean floor. Marine biologists have long noted that they create the sort of chemically rich and energy intensive environment around them that mimics the electrochemical conditions found in cells. So ... maybe (thinking that thought in reverse) the cells of the world are indeed to this day mimicking that sea floor environment. In this context, with the vents themselves offering abundant energy, scientists can model the creation of RNA molecules, some of which prove to be self-replicating, although in a highly imperfect fashion. Does it make sense to call this already "life"? Probably not. Call it "proto-life" if you will. There is some irony here, though. We often think of life as paradigmatically bound up with the absorption of sunlight. Light, through photosynthesis, becomes plant mat...