These definitions come from various pages of Stuart Kauffman’s book “Investigations”, a highly tentative outline of what he calls “a general biology”, i. e. one not dependent on Earthly materials or conditions – a biology that could apply anywhere in the Universe.
Page 32: “Life is based on collectively autocatalytic sets of molecules, not on template reproduction per se.” This means that a purely protein-based world could have preceded even an RNA world, although RNA can be both an enzyme and a template. Moreover, it means that on extraterrestrial planets, some other complex macromolecules could take the place of proteins, RNA and DNA, if they can form complex collectively autocatalytic networks.
Page 35: “Life is an expected, emergent property of complex chemical reaction networks. Under rather general conditions, as the diversity of molecular species in a reaction system increases, a phase transition is crossed beyond which the formation of collectively autocatalytic sets of molecules suddenly becomes almost inevitable. If so, we are birthed of molecular diversity, children of second generation stars.” [Second generation stars produced CHNOPS, the elements of life.] This is like “the Virgin birth of us all”.
Again, on page 46: “Life is an expected emergent pro perty of complex chemical reaction networks.”
Page 72: “Autonomous agents may constitute a proper definition of life itself”. Supplementing that, on page 8 is a definition of an autonomous agent: “A molecular autonomous agent is a self-reproducing molecular system able to carry out one or more thermodynamic work cycles.” It can do so by coupling exothermal reactions (stemming ultimately from sunlight) with endothermal reactions which build up complex molecules of its body from simple molecules (food). [Proteins from amino acid, complex carbohydrates from glucose, fats from fatty acids, nucleic acids from mononucleotides.] There is a further discussion of thermodynamic work cycles, based on the Carnot cycle. still further, “work cycles cannot occur at equilibrium’.’. It follows that “an autonomous agent must be displaced from thermodynamic equilibrium.”
Page 48: “This non-equilibrium flow into a persistent adjacent possible may be the proper arrow of time, rather than the more familiar appeal to the second law of thermodynamics in closed thermodynamic systems.” In other words, life tends to proliferate and spread. Later in the book, he postulates “a fourth law of thermodynamics”, which states that a biosphere will tend to expand “as fast as possible”, i.e. without disrupting itself. One gets a picture of a spreading contagion. But’ I don’t see how the second and the fourth law can be reconciled. After all, while life decreases its own internal entropy, it thereby increases the entropy of the environment even faster than would otherwise be the case. I would think that life is a spatially and temporally limited system, a transitory and local fluctuation. But Kauffman would disagree with my view.
Page 86. “Maxwell’s demon is almost an autonomous agent.” This is a fictitious creature who can sort fast from slow molecules of a gas and thereby negate the second law of thermodynamics. But the demon cannot perform a work cycle because the gas system is at equilibrium. (Pages 81-82.) On page 83 it is stated that “work is the constrained release of energy, but it often takes work to construct the constraints.”
Kauffman states in many places that the evolution of a biosphere cannot be predetermined; it is contingent on a changing environment, which is being changed by the evolution of the biosphere itself. (This is co-evolution.) This is an indeterminacy quite different both from the Heisenberg uncertainty principle and the evolution of chaos. On page 152 he states: “The biosphere is profoundly contingent upon history.” And “History enters when the space of the possible that might have been explored is larger, or vastly larger, than what has actually occurred.”
Kauffman’s exploration of the origin and nature of life rings true to me. I am even prepared to accept that the transition to life, with its vastly increased complexity , is actually easy and frequently occurring, not rare in the Universe. Probably, we are not alone; even though our fellow creatures may be only lowly bacteria. However, when Kauffman diverges into creativity of the Universe itself, in its creation of complexity, I get lost – partly through not understanding his theories, partly because of my perceived lack of credibility of what I do understand. The Universe itself is not alive; life forms only green islands in a vast blackness. Why should that not be enough?