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There is now a CONTENT FREEZE for Mercury while we switch to a new platform. It began on Friday, March 10 at 6pm and will end on Wednesday, March 15 at noon. No new content can be created during this time, but all material in the system as of the beginning of the freeze will be migrated to the new platform, including users and groups. Functionally the new site is identical to the old one. webteam@gatech.edu
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During the evolution of multicellularity, groups of cells evolve increased complexity by accruing group-level adaptations. Developmental systems play a crucial role in this process, providing a heritable basis for novel multicellular traits. Yet this poses a dilemma: how do multicellular organisms gain the capacity to adapt prior to the origin of genetically-encoded developmental systems, which are themselves a multicellular adaptation? In this talk, I will show that the nearly universal statistics of cellular packing from stochastic cellular reproduction can solve this problem by scaffolding the emergence of novel, heritable multicellular structures. In particular, the distribution of cellular free volumes in early multicellular groups should follow the maximum entropy principle. As a result, properties of multicellular groups that depend on cellular packing should become highly reproducible, and thus heritable. We test this theory using experimentally-evolved multicellular yeast, finding that the distribution of free volumes closely fits maximum entropy predictions and, combined with weakest link theory, correctly predicts the narrow distribution of group sizes generated during growth. Further, we demonstrate that these statistical properties are general, accurately describing diverse, independently-evolved multicellular organisms such as volvocine algaes. Our results highlight the importance of cellular packing in the transition to multicellularity, demonstrating how the emergent physics of multicellular collectives establishes groups as a ``Darwinian material’’ capable of multicellular adaptation prior to the evolution of genetically-encoded multicellular development.
