How did molecules form self-replicating systems? This is a harder problem than we sometimes think because it’s not obvious why molecules should seek to develop into complex organisms that can self-replicate. Science journalist Katharine Sanderson notes that University of Glasgow chemist Lee Cronin is using robots to test the “billions of ways” it could have happened:
He and his team have set up machines that combine a selection of simple substances – acids, inorganic minerals, carbon-based molecules – to react randomly. The outcome is analysed and then an algorithm helps the robot choose how to proceed. In this way, the robot can hunt through vast swathes of chemical space to see if any self-replicating systems emerge. Cronin thinks this automated strategy could overcome the biggest hurdle facing chemists in this field: “To remove the bias from the experimenter and see how evolutionary principles manifest in simple chemistry.”Katharine Sanderson, “How artificial intelligence can help us figure out how life began” at New Scientist (March 2, 2022)
One hope is that if an origin of life can be recreated, we would be in a better position to look for life on other planets. Kronin favors Venus as a place to look (“maybe almost alive but not quite”):
Anderson also tells us that
Cronin has also developed a way of assigning molecules a score that reflects their complexity. Get beyond a certain score, and the molecule could only have arisen from a life-like process, he argues. “It will give a yes or no answer to if something is alive or not,” he says.Katharine Sanderson, “How artificial intelligence can help us figure out how life began” at New Scientist (March 2, 2022)
Such a score might, of course, take us into deeper waters. For one thing, life cannot be simply reduced to chemistry. That is because in a universe where everything is running down (entropy), life violates entropy via self-replication. Something is happening which goes beyond chemistry so if Cronin finds it, he will probably not be finding only chemistry.
His approach is based on a concept he calls the molecular assembly index, a measure of the number of “steps” needed to attain a given molecule. The more complex the molecule, the higher its index — which mean the lower the probability that it formed by chance.
Cronin posits an assembly index of 15–20 as the cut-off, which would mean that one molecule formed by chance in a mole of a substance. The simplest amino acid, glycine, has an index of 4, but the energy currency of the cell, ATP. has an index of 21, which implies that it was not the product of chance processes. His paper on the topic is open access.
While many researchers believe that natural selection acting on random mutations (Darwinism) could cause life to form, it’s worth noting that, prior to the existence of life, there is nothing doing the selecting and nothing to select.
It’s not clear how the robots — themselves entirely a product of design — can help with that one.
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