In studies of the "RNA world," a theoretical early stage in the origin of life where RNA molecules played a crucial role, researchers have observed that parasitism is a common phenomenon. This means that some molecules can exploit others for their own benefit, which could lead to the extinction of those being exploited unless certain protective measures are in place, such as separating the molecules into compartments or arranging them in specific patterns.
By thinking of RNA replication as a kind of active process, similar to a computer running a program, researchers can explore various strategies that RNA might use to adapt to challenges in its environment. The study uses computer models to investigate how parasitism emerges and how complexity develops in response.
Initially, the system starts with a designed RNA molecule that can copy itself and occasionally makes small mistakes (mutations) during this process. Very quickly, shorter RNA molecules that act as parasites appear. These parasites are copied more rapidly because of their shorter length, giving them an advantage. In response, the original replicating molecules also become shorter to speed up their own replication. They develop ways to slow down the copying process, which helps reduce the advantage parasites have.
Over time, the replicating molecules also evolve more complex methods to distinguish between their own copies and the parasites. This complexity grows as new parasite species keep arising, not from evolving existing parasites, but from mutations in the replicating molecules themselves.
The process of evolution changes as well, with increases in mutation rates and the emergence of new mutation processes. As a result, parasitism not only drives the evolution of more complex replicators but also leads to the development of complex ecosystems. In summary, the study shows how parasitism can be a powerful force that promotes complexity and diversity in evolving systems.