Two separate laboratory breakthroughs have produced RNA molecules that can build copies of themselves or assemble functional structures without any help from proteins or DNA. These results offer the strongest experimental evidence yet that life on Earth may have started with self-replicating RNA alone, lending new weight to the long-debated RNA world hypothesis. But the findings also expose a gap between what happens in a controlled lab and what could have survived on a violent, young planet.
RNA That Copies and Evolves on Its Own
For decades, origin-of-life researchers have faced a chicken-and-egg problem: DNA needs protein enzymes to replicate, yet proteins need DNA instructions to be built. RNA offered a theoretical escape because it can both store genetic information and drive chemical reactions, a dual capability that could have allowed it to perform the earliest genetic and catalytic roles before the modern DNA–protein system existed. The discovery of ribozymes, RNA molecules with enzyme-like activity, showed that RNA is not just a passive messenger. Under the RNA world hypothesis, one key function of these ribozymes would have been to replicate other RNA sequences as templates to make complementary strands, setting up a primitive form of heredity and variation long before cells appeared.
Turning that theory into a working demonstration has been the challenge. Gerald Joyce and colleagues at the Salk Institute for Biological Studies used directed evolution to produce an RNA polymerase ribozyme that can propagate a functional RNA through repeated rounds of copying and selection. In practical terms, this molecule copies other RNA accurately enough to enable Darwinian evolution in an RNA-only system: its products are faithful enough for useful traits to persist, yet imperfect enough that new variants appear and can be selected. Reporting on the work notes that the team’s next milestone is a polymerase that can replicate itself as well as other RNAs, which would close the loop on fully autonomous self-replication. As covered in a recent account of the experiment, that threshold has not yet been reached, underscoring the difference between a sophisticated lab construct and a free-living ancestor of all biology.
Amino Acid Bridges and Self-Assembling Ribozymes
A second line of research, led by Jack Szostak’s former group, attacks a different piece of the puzzle: how complex catalysts might assemble from simpler parts. In work published in Science Advances, the team described a self-sustaining chimeric ribozyme composed of long RNA pieces bridged by intervening amino acids, forming a hybrid of genetic and protein-like chemistry. Rather than relying on a single continuous chain, this catalyst stitches itself together from shorter RNA fragments linked by amino acids, and it does so through an autocatalytic cycle in which the product helps accelerate its own formation. The result is a system where a small initial amount of the ribozyme can trigger more efficient assembly of the same structure, hinting at how prebiotic chemistry could bootstrap itself toward greater complexity.
What makes this molecule especially striking is its ability to assemble other ribozymes in trans, not just copies of itself. That capacity suggests a plausible route from isolated self-assembling molecules to cooperative molecular networks, a step that would be necessary for any pre-biological chemistry to resemble metabolism. The amino acid bridges also hint at how the transition from an RNA-only world to one that incorporated proteins might have begun, since the chimeric structure already integrates both types of building block. Scientists’ best-supported scenario remains that life emerged from self-replicating RNA strands that eventually evolved the ability to build proteins, and this chimeric ribozyme provides a first experimental glimpse of how that handoff might have looked in molecular terms.
Surviving Early Earth’s Harsh Conditions
Even if RNA can copy itself and assemble functional structures in a laboratory, the early Earth was no sterile bench. Temperatures swung wildly, ultraviolet radiation was intense, and liquid water itself posed a threat because it can break apart the chemical bonds holding RNA together. One proposed solution is that longer RNA chains could have taken refuge in porous rocks near volcanic sites, where mineral surfaces and confined spaces would have shielded fragile molecules from degradation while concentrating them enough to react. A recent analysis of this scenario argues that such geological microenvironments could help resolve a “genetic paradox”: how long, information-rich polymers might persist long enough to be copied and improved by selection in a world otherwise hostile to delicate nucleic acids.
Separate work on the so‑called water problem reinforces this idea from a different angle. A follow-up study found that when wet–dry cycles repeatedly expose simple building blocks to evaporation and rehydration, the resulting conditions can actually promote the formation of nucleic acids such as RNA rather than simply destroying them. Under these fluctuating regimes, condensation reactions that link nucleotides together become more favorable, and the newly formed strands can be partially protected within microscopic films and pores. Researchers reported that such wet–dry cycles might therefore have acted not only as a stressor but also as a creative force, driving the emergence of longer RNA chains in shallow pools or volcanic hot springs. Together with the rock-pore hypothesis, these findings sketch a more forgiving picture of early Earth, where the same harsh processes that threatened fragile molecules could also have supplied the energy and concentration needed to assemble them.
From Molecules to Protocells
Self-copying RNA and self-assembling ribozymes are necessary ingredients for life, but they are not sufficient on their own. To move from chemistry to biology, these molecules would have needed to become encapsulated in compartments that could grow, divide, and compete. Modern origin-of-life research explores how fatty acids and related lipids, which can form vesicles spontaneously in water, might have provided such primitive containers. Within these tiny bubbles, replicating RNA could have been kept close to its own products, allowing successful combinations of sequences and catalysts to persist together. Experimental programs at dedicated centers such as the origins-of-life initiative in Chicago are now combining work on ribozymes, membranes, and energy sources to test whether simple protocells can emerge from realistic mixtures of prebiotic ingredients.
The new ribozyme systems slot into this broader picture as potential “engines” inside early protocells. An RNA polymerase that can copy many different sequences could maintain a small genome of functional RNAs, while a chimeric catalyst that assembles other ribozymes could help diversify the internal chemistry of a compartment. If wet–dry cycles or rock pores periodically concentrated protocells and their contents, selection might favor those that replicated more reliably or harnessed environmental energy more effectively. Over time, this could transform a loose network of replicating strands into a population of competing micro-environments, edging closer to something we would recognize as living. In that sense, the recent breakthroughs are not isolated curiosities but test cases for how far chemistry can go before biology takes over.
What the Breakthroughs Do and Don’t Prove
Taken together, the polymerase ribozyme and the chimeric self-assembler represent a leap in our ability to build life-like systems from RNA. They show that unassisted nucleic acids can, under the right conditions, carry out copying, evolution, and cooperative assembly, three pillars of living systems. They also provide concrete targets for further refinement: more accurate copying, faster autocatalysis, and eventually the capacity for a single RNA network to maintain and reproduce itself without human intervention. Each incremental improvement tightens the connection between what we can do in glassware and what might once have happened in warm ponds, hydrothermal vents, or volcanic pools on the young Earth.
At the same time, these achievements highlight how much remains unknown. The lab-built ribozymes are products of intense human-guided selection, not spontaneous products of raw geochemistry, and they operate in carefully tuned solutions rather than muddy, mineral-rich environments. No experiment yet shows a fully autonomous, open-ended evolutionary system of RNAs that can arise, persist, and diversify without outside help. The gap between today’s demonstrations and a complete origin-of-life scenario is still wide. Yet by revealing that RNA alone can shoulder more of life’s essential tasks than previously proven, the new work narrows that gap and offers a more detailed roadmap for future experiments. Each step brings the abstract idea of an RNA world closer to a testable, experimentally grounded story of how life began.
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*This article was researched with the help of AI, with human editors creating the final content.
