The emergence of cellular organisms occurred sometime between the origin of life and the evolution of the last universal common ancestor and represents one of the major transitions in evolutionary history. Here we describe a series of artificial life simulations that reveal a close relationship between the evolution of cellularity, the evolution of metabolism, and the richness of the environment. When environments are rich in processing energy, a resource that the digital organisms require to both process their genomes and replicate, populations evolve toward a state of non-cellularity. But when processing energy is not readily available in the environment and organisms must produce their own processing energy from food puzzles, populations always evolve both a proficient metabolism and a high level of cellular impermeability. Even between these two environmental extremes, the population-averaged values of cellular impermeability and metabolic proficiency exhibit a very strong correlation with one another. Further investigations show that non-cellularity is selectively advantageous when environmental processing energy is abundant because it allows organisms to access the available energy, while cellularity is selectively advantageous when environmental processing energy is scarce because it affords organisms the genetic fidelity required to incrementally evolve efficient metabolisms. The selection pressures favoring either non-cellularity or cellularity can be reversed when the environment transitions from one of abundant processing energy to one of scarce processing energy. These results have important implications for when and why cellular organisms evolved following the origin of life.

细胞生物的出现发生在生命起源和最后一个祖先的进化之间，它代表了进化史上的主要转变之一。在这里，我们描述了一系列人工生命模拟，揭示了细胞进化，新陈代谢进化和环境丰富度之间的密切关系。当环境中的加工能量丰富时，数字有机体既需要处理它们的基因组又需要复制这些资源，种群便会朝着非细胞状态发展。但是，当环境中不容易获得加工能并且有机体必须从食物难题中产生自己的加工能时，人们总会进化出高效的新陈代谢和高度的细胞不渗透性。即使在这两个极端环境之间，细胞不渗透性和代谢能力的群体平均值也显示出非常强的相关性。进一步的研究表明，当环境处理能量丰富时，非细胞性具有选择性优势，因为它允许生物体获取可用能量；而当环境处理能量匮乏时，非细胞性则具有选择性优势，因为它为生物体提供了逐步进化有效代谢所需的遗传保真度。 。当环境从丰富的处理能之一转换为稀缺的处理能之一时，有利于非细胞性或细胞性的选择压力可以逆转。