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Universal ancestor only half alive?

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From Michael Le Page at New Scientist:

Many of the genes in our cells evolved billions of years ago and a few of them can be traced back to the last common ancestor of all life.

Now we have the best picture yet of what that ancestor was like and where it lived, thanks to a study that identified 355 genes that it probably possessed.

Half alive?

One characteristic of almost all living cells is that they pump ions across a membrane to generate an electrochemical gradient, then use that gradient to make the energy-rich molecule ATP. Martin’s results suggest LUCA could not generate such a gradient, but could harness an existing one to make ATP.

That fits in beautifully with the idea that the first life got its energy from the natural gradient between vent water and seawater, and so was bound to these vents. Only later did the ability to generate gradients evolve, allowing life to break away from the vents on at least two occasions – one giving rise to the first archaea, the other to bacteria. More.

Not clear how this volcanic vent thesis relates to being “half alive.” The LUCA may have featured a lower level of information but the main thing that characterizes a life form is the drive to stay alive.

Critics of such theories 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.

See also: Hydrothermal vent models make life inevitable?

What can we hope to learn about animal minds? (the drive in all life forms to go on existing)


Origin of life: Could it all have come together in one very special place? (hydrothermal vents)

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