Theoretical origin of life: a very different approach (Introduction)

by David Turell , Monday, March 06, 2023, 15:00 (418 days ago) @ David Turell

Ocean hydrothermal vents are absolutely the spot:

https://aeon.co/essays/why-life-is-not-a-thing-but-a-restless-manner-of-being?utm_sourc...

"For decades, most origin-of-life research has focused on how such self-replicating chemistry could have arisen. They largely brushed aside the other key question, how the first living things obtained the energy to grow, reproduce and evolve to greater complexity.

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"within modern organisms there is another clue to life’s origins, one that is more obscure than DNA but just as universal – the way cells harvest energy by shuffling around electrically charged molecules. This process goes by the mouthful ‘chemiosmosis’, and was first proposed in 1961 by the eccentric British biochemist Peter Mitchell. Chemiosmosis lacks the coded rigour of DNA, but that primal messiness might be exactly what makes it so revealing.

"Energy, Russell thinks, must have preceded anything resembling DNA or RNA, so the origin of chemiosmosis could help to reveal how the first organisms arose. Chemiosmosis takes place deep in our body’s cells, most of which harbour hundreds or thousands of microscopic structures called mitochondria. The mitochondria extract the chemical energy from food and, with the help of the oxygen we breathe, convert it into a molecule called adenosine triphosphate (ATP). Just as much as DNA, ATP is the molecule of life; it is the currency we spend to grow, move or think.

"No replication-focused origin-of-life theory has yet provided good explanation for the parallel origin of the elaborate machinery of chemiosmosis.

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"From Martin’s perspective , it made perfect sense that chemiosmosis came first, before RNA. ‘When you look at a group of organisms – in this case all life as we know it – and there is a property that is present in all forms, you put this property in the common ancestor. And that common property is harnessing an ion gradient,’ he says.

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"The expanded chemical garden hypothesis addressed another key question about the origin of life: how molecular building blocks become concentrated enough to react and link up with each other. Russell predicted there would be a temperature gradient across ocean-vent rocks – cool on the outside, warm on the inside. That gradient would have promoted a convective process called thermophoresis, which traps larger organic molecules in the compartments, encouraging the formation of sugars, amino acids, lipids and nucleotides – the building blocks of life. At the intense temperature and pressure of the deep sea, such building blocks inevitably began to link up, forming larger and more intricate molecules.

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"Over the next 15 years, more data began to pile up in support of life’s origin in a chemical garden. In one major change, most researchers are now convinced that life’s universal ancestor was an autotroph – meaning it made its own food from inorganic matter – just as Russell and Martin had predicted. A 2015 genomic study provided the most convincing evidence to date. An analysis of nearly 40 genes strongly suggested that the most ancient microbes generated methane from carbon dioxide and hydrogen. This analysis dovetails with geological work showing that methane formed by biological processes is the earliest organic compound found in ancient rocks.

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"...past the half-mile mark on the depth gauge. Suddenly, the vehicle’s lamps illuminated something utterly unexpected: a cluster of otherworldly pinnacles rising from the ocean floor, as tall as 20-storey buildings. Shimmering plumes of heated water billowed from their tops like smoke from chimneys. This strange landscape turned out to host an exotic ecosystem of snails, crabs, worms and shellfish, sustained by microbes that convert raw elements from the inner Earth into life without any help from the Sun. This field of hydrothermal vents, dubbed the Lost City, conformed almost exactly to Russell’s 1983 predictions. His chemical gardens had been found.

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"Over the next 15 years, more data began to pile up in support of life’s origin in a chemical garden. In one major change, most researchers are now convinced that life’s universal ancestor was an autotroph – meaning it made its own food from inorganic matter – just as Russell and Martin had predicted. A 2015 genomic study provided the most convincing evidence to date. An analysis of nearly 40 genes strongly suggested that the most ancient microbes generated methane from carbon dioxide and hydrogen. This analysis dovetails with geological work showing that methane formed by biological processes is the earliest organic compound found in ancient rocks.

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"Without energy gradients, even if all the right ingredients are in the right place for an RNA world, life cannot just appear. The implication is that biological information systems – the codes needed for life to reproduce – cannot just spring into existence. ‘The key to the beginning of living systems is to generate this energy storage conformation system, and to use the same energy machine to build the storage of information through DNA and RNA,’ Karsenti explained. ‘I would say energy came first.'’ (my bold)

Comment: An important new view of how to look at the problem. Note the bold. A just-so story of how deeply complex genetic information just falls into place.