Primordial evolvability: Impasses and challenges

Area of Science:

• Origin of Life Studies
• Biochemistry
• Systems Chemistry

Background:

• Metabolism-first approaches propose self-replicating molecules as life's precursors.
• The Graded Autocatalysis Replication Domain (GARD) model, based on amphiphilic molecules, is a prominent example.
• Previous simulations suggested GARD lacks selectability, questioning its evolutionary potential.

Purpose of the Study:

• To analyze the evolvability of the GARD model and similar metabolism-first scenarios.
• To identify limitations in GARD's chemical assumptions for origin of life research.
• To compare GARD's evolvability with alternative models like reflexively autocatalytic networks.

Main Methods:

• Evolutionary simulations of the GARD model.
• Analysis of chemical kinetics and network dynamics.
• Comparison of GARD with reflexively autocatalytic networks.

Main Results:

• GARD model lacks true evolvability; selection has minimal impact.
• Non-covalent bond chemistry and random catalytic interactions in GARD hinder autocatalysis.
• Lognormal distribution of catalytic factors leads to kinetic instability.
• Reflexively autocatalytic networks, utilizing covalent bond formation/breakage, demonstrate superior evolvability.

Conclusions:

• GARD model is unlikely to be a viable precursor to life due to inherent limitations.
• Open-ended evolvability requires chemical reactions forming/breaking covalent bonds, not just incorporation.
• Reflexively autocatalytic networks represent a more plausible pathway for the origin of life.