A hallmark of life is the way information flows between different levels of organization. In non-living systems, information flows from the bottom up–the properties of the individual parts determine the fate of the system.
But with living systems, that flow goes both ways. Not only genes dictate the nature of proteins which in turn affect the functioning of cells, tissues and organisms, but the behavior of proteins, cells, and organisms also control gene expression. This is what Walker calls “top-down control” or “top-down causation.”
And to Walker, this transition–from information seeping upward only to information flowing both up and down–is the key to understanding life’s origins. Put differently, the blueprint for building an organism isn’t stored in its DNA only, but it’s distributed in the state of the entire system.
And when it comes to basic chemical networks, Walker thinks, that distribution is something we could potentially measure.
She is looking at “integrated information,” a measure University of Wisconsin neuroscientist Giulio Tononi thinks can calculate how much integrated information a network carries, a quantity he calls “phi.”
All this is as much as to say that the problem of the origin of life is a problem in the origin of information. Software engineer Arminius Mignea’s specifications for a simplest self-replicator in Engineering and the Ultimate would be a useful read, to get some sense of what is required (a brief introduction here).
See also: With Enceladus the toast of the solar system, here’s a wrap-up of the origin-of-life problem
The Science Fictions series at your fingertips (origin of life)
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