Recently, I reviewed origin-of-life articles published over the past few years. The publications did little to inspire confidence that the field is making progress toward explaining how any significant step in abiogenesis is even remotely plausible. Moreover, despite numerous concerns raised about the direction of the field (here, here, here), investigators continue to recycle the same failed models, repackaging them with new chemical narratives, more elaborate experimental setups, and slicker marketing.
The representative example I will address here is chemist Yongdong Jin’s article, published in the AAAS (American Association for the Advancement of Science) journal Research, titled “On the Origin of Life on Earth: The Nanozymes Hypothesis, and More.”
Provocative Proposal
Jin proposes that microscopic particles, which he terms nanozymes, orchestrated many of the major steps in the synthesis of the first cell. He asserts that these versatile molecules catalyzed metabolic reactions, generated and confined biological molecules, harnessed solar energy, and synthesized proteins, RNA, and DNA:
The initial inorganic MN-zymes catalyze the syntheses of the initial small (bio)molecules and can polymerize the formation of longer (bio)molecules (oligomers) on their surfaces, while in later stage, proteins, DNA, and RNA precursors or analogs can be spontaneously formed almost simultaneously at a certain stage (the Big Bang of molecular diversity), as a result of catalytic diversity caused by increasingly abundant and iterated inorganic/organic hybrid nanozymes.
Nanozyme Nonsense
Par for the course, most of Jin’s claims are based on overinterpretation of previous studies:
- Polymerization: He references the experimental results of Ferris et al. (1996) to justify inorganic molecules assisting in the formation of long nucleotide chains, the precursors of RNA. But the experiment required a constant supply of high concentrations of activated nucleotides onto manufactured mineral surfaces. The study could only produce long chains under carefully controlled and highly unnatural conditions; it did not demonstrate what could have occurred on the ancient Earth (here, here).
- Photosynthesis: Jin relies heavily on Mulkidjanian’s (2009) “Zinc World” hypothesis to argue that UV-irradiated ZnS could reduce CO₂ and supply organic compounds. He confidently asserts that “inorganic photosynthesis…undoubtedly played a vital role in the long history of the primordial OoL on Earth.” Here again, spontaneous photosynthesis at significant rates has only been observed using highly orchestrated experimental protocols. For instance, Zhang (2007) employed colloidal ZnS under specified UV radiation in the presence of a sulfur “hole scavenger,” with carefully selected pH and inorganic-carbon concentration. The early Earth could never have been so accommodating.
- RNA-peptide production: Jin references Müller et al. (2022) to posit that ancient self-replicating RNA could have linked amino acids into peptides (protein precursors), jump starting cellular metabolism. But no aspect of this research even remotely corresponds to what could transpire through prebiotic chemistry. In fact, the RNA-peptide model brings together the most implausible features of both the RNA World and Protein World hypotheses. I detail the enormous investigator intervention required by Müller et al. (2022) in my article “Another Claim by Origin-of-Life Researchers Dissolves on Inspection.”
Jin makes several other inferential leaps from limited laboratory observations to solutions of much larger problems in abiogenesis. In addition to the previous examples, he exaggerates the results of research on chirality, compartmentalization, and wet–dry cycling. He does concede that evidence from artificial gold-nanoparticle nanozymes “may be overextended to prebiotic conditions.” But the same types of qualifications apply to his other claims.
Inescapable Impediments
Neither the nanozyme hypothesis nor any other model can overcome three key impediments to life’s origin through undirected processes:
- A minimally complex autonomous cell represents a fantastically improbable arrangement of molecules. Estimates of the chance of randomly arranged molecules corresponding to a self-sustaining cell are far smaller than 1 in 10 to the power of 1,000,000,000 (1 with a billion zeros after it).
- Thermodynamic processes drive chemical systems away from life, never toward it. Any arrangement of molecules corresponding to a state intermediate between thermal equilibrium and a cell would spontaneously decompose and move back toward equilibrium (here, here, here).
- Energy sources on the early Earth and available molecules that bias chemical reactions are too indiscriminate to assist life’s origin. They would always move a chemical mixture toward a uselessly complexity (here, here).
The only explanation for the first cell — an autonomous nanovessel capable of energy production, information processing, and much more — is a mind vastly superior to our own.