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Autocatalytic networks offer one possible way for organized chemistry to arise before cells, proteins and RNA: reactions can form a mutually supporting system in which the products of some reactions help catalyze others. Researchers have identified structures with this pattern in modern microbial metabolism. That makes the idea scientifically testable, but it does not show that such a network existed on early Earth or that it was the first step toward life.
What an autocatalytic network is
In an autocatalytic network, molecules participate in reactions that produce molecules which, in turn, help catalyze reactions in the network. The key idea is collective self-support: the network’s reactions can sustain the availability of catalysts and products needed for further reactions.
This does not necessarily mean that one molecule makes an identical copy of itself. A network may instead produce different molecules that collectively help catalyze one another’s formation. Nor does the label alone establish that the chemistry would persist in a particular environment, grow, or evolve into life.
How RAF theory defines the pattern
Reflexively autocatalytic and food-generated (RAF) theory gives the idea two formal tests. A proposed RAF is evaluated relative to a specified set of starting compounds, called the food set, and a specified pattern of which molecules catalyze which reactions.
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Reflexively autocatalytic
Every reaction in the set must have at least one catalyst that is either in the food set or produced by reactions in the set. The reactions are therefore catalyzed using resources available from the starting materials or from the network itself.
Food-generated
The reactants needed by the network’s reactions must be buildable from the food set using reactions in the set. The network cannot depend on a required reactant that it has no way to obtain from its starting materials and reactions.
Satisfying both criteria is a mathematical property of a reaction network under those assumptions. It is not, by itself, proof that the network would operate under real environmental conditions or have the persistence and other properties associated with life. Hordijk and Steel’s 2018 review explains this distinction between formal network properties and life-like behavior.
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What the microbial metabolism findings show
A 2020 study in Proceedings of the Royal Society B, “Autocatalytic chemical networks at the origin of metabolism,” searched metabolic networks of living microbes for RAF structures. The authors reported RAFs in the metabolism of ancient anaerobic autotrophs. In their analysis, when supplied with small-molecule catalysts, these networks could generate acetyl-CoA as well as amino acids and bases.
The study also reported that amino acids and bases, without organic catalysts, did not generate metabolic RAFs in its analysis. The authors interpreted their results as consistent with an autotrophic origin of metabolism and proposed that autocatalytic chemical networks may have preceded proteins and RNA.
These results show that RAF patterns can be identified in modern microbial metabolic networks and can inform hypotheses about early metabolism. They do not amount to observing a prebiotic network: the networks analyzed belong to extant organisms, and the study uses their structure to investigate what may be relevant to origins.
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What remains unproven about early Earth
The central historical question is whether smaller autocatalytic networks actually existed as intermediates before life, and whether they could have developed into more complex biological systems. The 2020 study states directly that “evidence for their role in prebiotic evolution is lacking.” Its findings therefore support a possible origin scenario, not a demonstrated sequence of events.
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- Suggested, not established: Autocatalytic chemistry may have contributed to early metabolism and may have preceded proteins and RNA.
- Not demonstrated: A specific RAF existed on early Earth, arose before other biological systems, or developed into the first life.
The word “could” matters: the proposal is plausible enough to study using formal network analysis, but the available findings do not establish it as the historical explanation for life’s origin.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How RAF research contributes to origin-of-life study
RAF theory makes a broad idea—chemical reactions supporting one another—more precise. Researchers can test whether a proposed reaction system meets the RAF criteria, examine how its structure changes with different food sets or catalyst assumptions, and compare network patterns with biochemical organization.
A 2020 methods paper, “The structure of autocatalytic networks, with application to early biochemistry,” developed tools for exploring and visualizing RAF structures and applied them to large metabolic networks from archaeal and bacterial lineages near early branches of the tree of life. This extends RAFs as an analytical framework for studying biochemical organization. It does not independently resolve whether RAFs were prebiotic intermediates.
Earlier work by Wim Hordijk and Mike Steel, including their 2017 review “Chasing the tail: The emergence of autocatalytic networks,” traces the concept to early proposals by Stuart Kauffman and surveys theoretical, computational and experimental work. Laboratory examples show that autocatalytic chemistry is not solely a mathematical abstraction; they are not, however, demonstrations of the historical origin of life.
How to assess claims about autocatalysis and evolution
When a study or popular account says an autocatalytic network could have played a role in life’s beginnings, separate the network result from the historical inference. Useful questions include:
- What compounds are assumed to be available as the food set?
- What catalyzes each reaction, and are those catalysts supplied or produced within the proposed network?
- Can the network build the reactants its reactions require from the food set?
- Is the claim about a formal network pattern, a laboratory reaction system, a modern organism’s metabolism, or chemistry on early Earth?
- What evidence connects the proposed chemistry to prebiotic conditions and to a transition toward life?
Those distinctions help explain both the value and the limits of RAF research: it can clarify how chemical organization might work without, by itself, establishing when or where such organization first arose.
Quick Recap
Further reading
- Hordijk and Steel, “Chasing the tail: The emergence of autocatalytic networks,” Biosystems 152 (February 2017).
- Hordijk and Steel, “Autocatalytic Networks at the Basis of Life’s Origin and Organization,” Life (2018).
- “Autocatalytic chemical networks at the origin of metabolism,” Proceedings of the Royal Society B (published March 11, 2020).
- “The structure of autocatalytic networks, with application to early biochemistry,” Journal of the Royal Society Interface (2020).
- For broader background on Kauffman’s ideas about self-organization, Stuart Kauffman’s At Home in the Universe: The Search for the Laws of Self-Organization and Complexity (Oxford University Press, 1995) predates modern RAF research and is not a current review of it.
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