Humankind has always been looking for an answer to the question of how life began and coming up with different theories on the origin of life. But now for almost two centuries, Darwin's theory of evolution has been shedding light upon many enigmas that were unknown to humans.
Inspired by the theory of evolution, researchers at the University of Tokyo conducted a long-term experiment on RNA replication and through this, they discovered a transition from a chemical system to biological complexity. Eventually, the research team created an RNA molecule that can not only reproduce but also "evolve" into a variety of more complicated molecules, according, to a study published in Nature Communications. This finding can give us clues about the early stages of evolution.
The new finding is a significant breakthrough in terms of Darwinism because the researchers experimented with a unique RNA replication system, which leads to a self-perpetuating process of continuous change based on mutations and natural selection.
The experiment included the incubation of RNA replicase molecules in droplets of water encased in oil at 98.6 °F for five hours at a time. And then the nutrients were added to be mixed before being put into an incubator for another five hours. This process was repeated up to 240 rounds. The result of this sequence analysis was that two RNA lineages branched into multiple sublineages of host and parasitic RNAs.
“Honestly, we initially doubted that such diverse RNAs could evolve and coexist,” commented Ryo Mizuuchi, corresponding author of the study. “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.”
A new insight into how life began
The study provides us with further insight into the first stages of evolution and a possible evolutionary route. It has also been proved that RNA can evolve and lead to complex life. The researchers intend to carry out additional research to learn more about how RNA may have paved the way for biological systems. “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 said.
In prebiotic evolution, self-replicating molecules are believed to have evolved into complex living systems by expanding their information and functions open-endedly. Theoretically, such evolutionary complexification could occur through successive appearance of novel replicators that interact with one another to form replication networks. Here we perform long-term evolution experiments of RNA that replicates using a self-encoded RNA replicase. The RNA diversifies into multiple coexisting host and parasite lineages, whose frequencies in the population initially fluctuate and gradually stabilize. The final population, comprising five RNA lineages, forms a replicator network with diverse interactions, including cooperation to help the replication of all other members. These results support the capability of molecular replicators to spontaneously develop complexity through Darwinian evolution, a critical step for the emergence of life.