Study Shows RNA Undergoing Darwinian Evolution

Researchers in Japan have created an RNA molecule that replicates, diversifies and develops complexity in line with the principles of Darwinian evolution. The findings provide the first empirical evidence that simple biological molecules can evolve into complex lifelike systems and supports the origin of life theory that RNA molecules began to self-replicate around 4 billion years ago, developing over time from a simple, single RNA molecule into diverse, complex molecules and higher forms of life.

Professors Ryo Mizuuchi and Norikazu Ichihashi and colleagues at the University of Tokyo set out to test this origin of life theory through a long-term RNA replication experiment. Their findings, published recently in Nature Communications, details RNA’s transition from a chemical system towards biological complexity. “We found that the single RNA species evolved into a complex replication system: a replicator network comprising five types of RNAs with diverse interactions, supporting the plausibility of a long-envisioned evolutionary transition scenario,” says Mizuuchi.

Compared to previous empirical studies, their results are novel because they used a unique RNA replication system that can undergo Darwinian evolution, i.e., a self-perpetuating process of continuous change based on mutations and natural selection. This enabled different characteristics to emerge, including adaptations to the environment for survival.

“Honestly, we initially doubted that such diverse RNAs could evolve and coexist,” says Mizuuchi. “In evolutionary biology, the ‘competitive exclusion principle’ states that more than one species cannot coexist if they are competing for the same resources. This means that the molecules must establish a way to use different resources one after another for sustained diversification. They are just molecules, so we wondered if it were possible for nonliving chemical species to spontaneously develop such innovation.”

Mizuuchi says the evolution of complexity seen in their experiment is just the beginning. “The simplicity of our molecular replication system, compared with biological organisms, allows us to examine evolutionary phenomena with unprecedented resolution… Many more events should occur towards the emergence of living systems.”

The findings provide an empirically based insight into a possible evolutionary route that an early RNA replicator may have taken on primitive Earth. “The results could be a clue to solving the ultimate question that human beings have been asking for thousands of years — what are the origins of life?” Mizuuchi adds.