Living cells are powered by a totally unexpected process. The energy from food is used to pump protons across a membrane to build up an electrochemical gradient. This gradient drives the machinery of life, like water from a dam driving a turbine.
And Lane argues that life has been powered by proton gradients from the very beginning. Forget all those primordial soups or “warm ponds”: only the natural proton gradients found in undersea alkaline hydrothermal vents could have provided the continuous flux of carbon and energy that life requires. These vents may be common on rocky planets so, if this reasoning is correct, simple cells should be too.
It’s the next step that is tricky. To become more complex, cells need more membrane to provide more energy. But the larger the area of membrane, the harder it is to keep control of the proton gradient – and losing control means death. So cells stayed simple. “There is no innate or universal trajectory towards complex life,” Lane writes.
Not, at least, until something extraordinary happened: one kind of simple cell somehow started living inside another. More.
See also: Origin of life: Could it all have come together in one very special place?:
Critics argue that hydrothermal vent fields are too hot and too acid for a promising soup of free-floating amino acids. A critic (who advocates ancient mud volcanoes instead) charges, “It’d be like trying to make life evolve from hot Coca-Cola.” Stanley Miller of Miller-Urey experiment fame told Discover Magazine in 1992 that overall, “The vent hypothesis is a real loser. I don’t understand why we even have to discuss it.” One difficulty is that the oldest known fossils are stromatolites, clumps of bacteria from 3.5 billion years ago, which suggests that life began in shallow seas, not deep ones. More.
A cheat sheet on origin of life
But the vents make way better vid than warm ponds do.
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