Evolving multicellularity in digital organisms through reproductive altruism

Abstract

The processes by which multicellular organisms first emerged from their unicellular ancestors are fundamental to the biology of complex, differentiated life forms. Previous work suggests that reproductive division of labor between specialized germ and soma cells was central to this evolution in some cases. Here, we use the digital life platform Avida to examine the trade-off between survival and replication in multicellular organisms. Avida uses a grid of self-replicating computer programs capable of mutation and evolution to address biological questions computationally. We model our digital organisms after the Volvocales, a flagellated order of photosynthetic green algae that includes both unicellular and multicellular species. We show that, given selective pressures similar to those experienced by the Volvocales in nature, digital organisms are capable of evolving multicellularity within the Avida platform. The strategies we observed that best handled the trade-off between survival and replication involved germ cells producing sterile, somatic offspring. These strategies are similar to those observed in volvocine algae, which suggests that digital platforms are appropriate to use in the study of reproductive altruism.