MarkE
2025-01-12 08:36:28 UTC
Yes/no/maybe? Or possibly as a precursor or complementary mechanism to
the RNA world?
"Autocatalytic sets have been an attractive alternative to the
“information-polymer-first” hypothesis since their introduction by
Kauffman. It offers a solution to the improbability of the formation of
self-replicating RNA. Simply put, forming many short cross-catalytic
molecules is statistically more likely than forming one highly efficient
self-replicator."
- Sergey Semenov
"It is consensual that life’s emergence necessitates an early appearance
of a self-copying chemical system. One scenario for that is “RNA-first,”
whereby life was seeded by a single polymeric self-replicating molecule.
Another scheme, conceived by Stuart Kauffman, contends that life was set
up by a supramolecular network that occasionally reaches catalytic
closure, leading to self-reproduction of an entire “collectively
autocatalytic set” (CAS)."
- Doron Lancet
"Autocatalysis is a particularly remarkable concept in that it allows us
to inspect the self-referential paradox in physical-chemical phenomena.
Cellular life is the epitome of material self-reference. Several authors
(including Kauffman, Dyson, Eigen, Schuster, Rosen, Ganti, Prigogine,
Maturana, and Varela) posited some form of collective autocatalysis or
chemical closure as central in the origins of life (OoL)."
- Joana Xavier
"It is true that some major researchers in the origin of life field have
given up in despair. I was stunned to learn this. The field is badly
fragmented. There is no overarching view around which many of us
disparate workers can think to organize work...If as a field, some
number of us could coordinate around creating such small molecule
collectively autocatalytic sets de novo, seeing how these might
co-evolve to include lipids, peptides, and RNA, then seeing how these
richer systems might co-evolve to template replication and coding, we
might find a pathway many of us could work on."
- Stuart Kauffman
Quotes above from:
https://www.sciencedirect.com/science/article/pii/S2666386423004022
_________
Regardless, there appear to be several compelling reasons why
autocatalytic sets won't work for OoL:
The concept of autocatalytic sets has been widely discussed as a
potential mechanism for the origin of life, particularly in the context
of abiogenesis. These sets consist of networks of molecules in which
each molecule is catalyzed by others in the set, allowing
self-sustaining chemical processes. While the concept has theoretical
appeal, it has also faced significant criticisms and challenges. Below
are some of the key criticisms:
1. Lack of Experimental Evidence
Criticism: Despite theoretical models, there is limited experimental
evidence demonstrating that autocatalytic sets can arise spontaneously
in prebiotic conditions and maintain stable, self-sustaining behavior.
- Implications: Without experimental validation, the plausibility of
autocatalytic sets as a pathway to life remains speculative.
2. Fragility of Autocatalytic Networks
Criticism: Autocatalytic sets are often considered fragile. If one or
more critical components are lost or degraded, the entire network may
collapse, raising doubts about their robustness in fluctuating prebiotic
environments.
- Implications: Early Earth conditions were dynamic and potentially
hostile, with UV radiation, hydrolysis, and other destructive forces,
making the stability of such networks questionable.
3. Complexity and Probability
Criticism: The formation of an autocatalytic network capable of
self-sustaining replication and evolution requires a sufficiently
diverse and complex set of molecules. The likelihood of such complexity
arising spontaneously is debated.
- Implications: Critics argue that even with favorable conditions, the
emergence of complex networks through random chemical interactions may
be implausibly rare.
4. Lack of Information Encoding
Criticism: Autocatalytic sets, as described in many models, do not
inherently encode information in a manner analogous to nucleic acids
like DNA or RNA.
- Implications: Without a mechanism for hereditary information transfer,
it is unclear how such sets could undergo Darwinian evolution and give
rise to life.
5. Transition to Modern Biochemistry
Criticism: Autocatalytic sets may explain early chemical
self-organization, but it remains unclear how such systems could
transition into modern biochemistry, which relies on templated
replication (e.g., RNA, DNA) and complex metabolic pathways.
- Implications: This "gap" between autocatalytic chemistry and the
RNA/protein world challenges their role as a comprehensive solution to
abiogenesis.
6. Energy Constraints
Criticism: Autocatalytic sets require energy to drive chemical
reactions. The source, concentration, and consistency of energy in
prebiotic environments remain speculative.
- Implications: Without a clear energy source or mechanism for energy
coupling, it is difficult to see how autocatalytic networks could
sustain themselves over time.
7. Dependence on Specific Conditions
Criticism: Some models of autocatalytic sets depend on idealized
conditions, such as specific concentrations of reactants, catalysts, or
environmental factors.
- Implications: Critics argue that these requirements may be too
restrictive or unlikely to have been consistently met on the early Earth.
8. Circular Logic
Criticism: The concept of autocatalytic sets assumes that catalysis and
molecular diversity already exist, but it does not fully explain how
these features arise in the first place.
- Implications: This creates a circular argument, where the existence of
an autocatalytic network presupposes the conditions needed to form it.
9. Compartmentalization Challenge
Criticism: For autocatalytic sets to evolve, they need to be physically
isolated to prevent the dilution of components and maintain localized
reactions (e.g., in vesicles or compartments). However, how such
compartmentalization occurred prebiotically is not well understood.
- Implications: Without compartmentalization, maintaining coherence and
identity in an autocatalytic set seems unlikely.
10. Lack of Specificity in Catalysis
Criticism: Most models assume generalized catalytic properties for
molecules in the set, but real-life catalytic activity often depends on
precise molecular structures and environmental conditions.
- Implications: The assumption of broad catalytic activity may
oversimplify the challenges of forming and maintaining autocatalytic
networks.
the RNA world?
"Autocatalytic sets have been an attractive alternative to the
“information-polymer-first” hypothesis since their introduction by
Kauffman. It offers a solution to the improbability of the formation of
self-replicating RNA. Simply put, forming many short cross-catalytic
molecules is statistically more likely than forming one highly efficient
self-replicator."
- Sergey Semenov
"It is consensual that life’s emergence necessitates an early appearance
of a self-copying chemical system. One scenario for that is “RNA-first,”
whereby life was seeded by a single polymeric self-replicating molecule.
Another scheme, conceived by Stuart Kauffman, contends that life was set
up by a supramolecular network that occasionally reaches catalytic
closure, leading to self-reproduction of an entire “collectively
autocatalytic set” (CAS)."
- Doron Lancet
"Autocatalysis is a particularly remarkable concept in that it allows us
to inspect the self-referential paradox in physical-chemical phenomena.
Cellular life is the epitome of material self-reference. Several authors
(including Kauffman, Dyson, Eigen, Schuster, Rosen, Ganti, Prigogine,
Maturana, and Varela) posited some form of collective autocatalysis or
chemical closure as central in the origins of life (OoL)."
- Joana Xavier
"It is true that some major researchers in the origin of life field have
given up in despair. I was stunned to learn this. The field is badly
fragmented. There is no overarching view around which many of us
disparate workers can think to organize work...If as a field, some
number of us could coordinate around creating such small molecule
collectively autocatalytic sets de novo, seeing how these might
co-evolve to include lipids, peptides, and RNA, then seeing how these
richer systems might co-evolve to template replication and coding, we
might find a pathway many of us could work on."
- Stuart Kauffman
Quotes above from:
https://www.sciencedirect.com/science/article/pii/S2666386423004022
_________
Regardless, there appear to be several compelling reasons why
autocatalytic sets won't work for OoL:
The concept of autocatalytic sets has been widely discussed as a
potential mechanism for the origin of life, particularly in the context
of abiogenesis. These sets consist of networks of molecules in which
each molecule is catalyzed by others in the set, allowing
self-sustaining chemical processes. While the concept has theoretical
appeal, it has also faced significant criticisms and challenges. Below
are some of the key criticisms:
1. Lack of Experimental Evidence
Criticism: Despite theoretical models, there is limited experimental
evidence demonstrating that autocatalytic sets can arise spontaneously
in prebiotic conditions and maintain stable, self-sustaining behavior.
- Implications: Without experimental validation, the plausibility of
autocatalytic sets as a pathway to life remains speculative.
2. Fragility of Autocatalytic Networks
Criticism: Autocatalytic sets are often considered fragile. If one or
more critical components are lost or degraded, the entire network may
collapse, raising doubts about their robustness in fluctuating prebiotic
environments.
- Implications: Early Earth conditions were dynamic and potentially
hostile, with UV radiation, hydrolysis, and other destructive forces,
making the stability of such networks questionable.
3. Complexity and Probability
Criticism: The formation of an autocatalytic network capable of
self-sustaining replication and evolution requires a sufficiently
diverse and complex set of molecules. The likelihood of such complexity
arising spontaneously is debated.
- Implications: Critics argue that even with favorable conditions, the
emergence of complex networks through random chemical interactions may
be implausibly rare.
4. Lack of Information Encoding
Criticism: Autocatalytic sets, as described in many models, do not
inherently encode information in a manner analogous to nucleic acids
like DNA or RNA.
- Implications: Without a mechanism for hereditary information transfer,
it is unclear how such sets could undergo Darwinian evolution and give
rise to life.
5. Transition to Modern Biochemistry
Criticism: Autocatalytic sets may explain early chemical
self-organization, but it remains unclear how such systems could
transition into modern biochemistry, which relies on templated
replication (e.g., RNA, DNA) and complex metabolic pathways.
- Implications: This "gap" between autocatalytic chemistry and the
RNA/protein world challenges their role as a comprehensive solution to
abiogenesis.
6. Energy Constraints
Criticism: Autocatalytic sets require energy to drive chemical
reactions. The source, concentration, and consistency of energy in
prebiotic environments remain speculative.
- Implications: Without a clear energy source or mechanism for energy
coupling, it is difficult to see how autocatalytic networks could
sustain themselves over time.
7. Dependence on Specific Conditions
Criticism: Some models of autocatalytic sets depend on idealized
conditions, such as specific concentrations of reactants, catalysts, or
environmental factors.
- Implications: Critics argue that these requirements may be too
restrictive or unlikely to have been consistently met on the early Earth.
8. Circular Logic
Criticism: The concept of autocatalytic sets assumes that catalysis and
molecular diversity already exist, but it does not fully explain how
these features arise in the first place.
- Implications: This creates a circular argument, where the existence of
an autocatalytic network presupposes the conditions needed to form it.
9. Compartmentalization Challenge
Criticism: For autocatalytic sets to evolve, they need to be physically
isolated to prevent the dilution of components and maintain localized
reactions (e.g., in vesicles or compartments). However, how such
compartmentalization occurred prebiotically is not well understood.
- Implications: Without compartmentalization, maintaining coherence and
identity in an autocatalytic set seems unlikely.
10. Lack of Specificity in Catalysis
Criticism: Most models assume generalized catalytic properties for
molecules in the set, but real-life catalytic activity often depends on
precise molecular structures and environmental conditions.
- Implications: The assumption of broad catalytic activity may
oversimplify the challenges of forming and maintaining autocatalytic
networks.