Selection for propagule formation in prebiotic chemical ecosystems

The formation of biological individuals on Earth is a complex process that likely began with the spontaneous emergence of simple cellular structures. However, these early cells were too intricate to have formed without assistance. Researchers have proposed a new hypothesis to explain how the first biological individuals could have emerged through the process of selection for propagule formation. This hypothesis suggests that the development of propagules could have been advantageous in specific environmental conditions.

The key conditions for the advantage of propagule formation were identified as 1) the distribution of sites supporting autocatalysis being far apart, and 2) the environment experiencing regular disturbances. To test this hypothesis, the researchers employed computational reaction-diffusion models to simulate surface-catalyzed autocatalytic systems in environments characterized by patchy landscapes and frequent disturbances.

Two competing autocatalytic cycles were examined, each made up of mutually beneficial subcycles. One of these subcycles was responsible for the production of propagules. The findings of the analysis revealed that propagules generally had a negative impact in environments that were well-mixed or where viable surfaces were too close together to reliably disperse through single-species dispersal.

However, the study showed that propagule formation became advantageous in environments where long stretches of empty space needed to be traversed to access new resources, or when environmental disturbances were common.

These results imply that spatial structure could have played a crucial role in selecting for reliable forms of codispersal, where propagules are dispersed alongside beneficial autocatalytic species. Over time, this mechanism could have led to the evolution of vesicles, which would have transported multiple autocatalytic species and eventually became independent protocells.

This proposed mechanism of propagule formation in prebiotic chemical ecosystems provides a potential explanation for the emergence of biological individuality on Earth.