Nick Lane is a biochemist who works on the origin of life at University College London (UK). He's also a science writer who recently won the Royal Society Prize for Life Ascending: The Ten Great Inventions of Evolution. His new book will be called, CHASM: The Outlandish Origins of Complex Life.
Lane is one of the main proponents of the "Metabolism First" view of the origin of life. The idea is that life began with the evolution of an energy source much like the main source of energy in today's cell. The energy is derived from a gradient of proton concentration across a membrane. This was first discovered by Peter Mitchell (chemiosmotic theory) and it was one of the most important discoveries in biochemistry—although most people, including most biochemists, haven't got a clue what it's all about [Ode to Peter Mitchell] [Why Are Cells Powered by Proton Gradients?] [Metabolism First and the Origin of Life ].
If this view is correct then the origin of life depends only on the presence of simple chemical systems that create an energy producing gradient and this is likely to happen on many planets. However, the leap from simple cells to complex cells may have been the rate-limiting step in the evolution of sentient beings.
Lane suggests that large complex cells with large genomes could only have arisen if they discovered an abundant source of energy. That happened when some simple bacteria formed an endosymbiotic relationship with bigger cells to create a new life form with mitochondria [Energetics and genetics across the prokaryoteeukaryote
divide]. This unique event was not inevitable. It happened only once in the history of life—about 2 billion years ago. This sort of lucky accident may never occur on other planets so it may just be a fluke that sentient beings evolved on Earth.
We may be alone in the universe.
