Robust heritability of collective traits via the maximum entropy principle

Multicellular organisms are pervasive and broadly successful. Their success is due in part to their complex structures and functions, which self-assemble through a genetically regulated multicellular development plan. However, early multicellular groups likely lacked the developmental genes necessary to ensure that group traits were heritable. Without developmental genes, cells divide stochastically, meaning that the final cellular configuration emerges at the whim of random events, making it unclear how nascent multicellular groups achieve heritable size and shape. Here, we propose that stochasticity supplied by random cell division can directly lead to highly heritably group traits. We find that experimentally evolved multicellular groups formed with fixed bonds via stochastic cell division achieve robust, heritable multicellular size and reproduction due to emergent statistics from entropic cellular packing. Our results indicate that emergent physics plays a critical role in establishing cellular groups as viable ``Darwinian materials’’, and that both stochastic growth and fixed bonds may have been crucial ingredients for many currently surviving branches of complex multicellularity.