The bottom-up approach to understanding the evolution of organisms is by studying molecular evolution. With the large number of protein structures identified in the past decades, we have discovered peculiar patterns that nature imprints on protein structural space in the course of evolution. In particular, we have discovered that the universe of protein structures is organized hierarchically into a scale-free network. By understanding the cause of these patterns, we attempt to glance at the very origin of life.
Abbreviations: PDUG, protein domain universe graph
Source: Dokholyan, N. V., Shakhnovich, B., & Shakhnovich, E. I. (2002). Expanding protein universe and its origin from the biological Big Bang. Proceedings of the National Academy of Sciences, 99(22), 14132–14136. https://doi.org/10.1073/pnas.202497999