Evolution of irreversible somatic differentiation

A key innovation emerging in complex animals is irreversible somatic differentiation: daughters of a vegetative cell perform a vegetative function as well, thus, forming a somatic lineage that can no longer be directly involved in reproduction. Primitive species use a different strategy: vegetative and reproductive tasks are separated in time rather than in space. Starting from such a strategy, how is it possible to evolve life forms which use some of their cells exclusively for vegetative functions? Here, we develop an evolutionary model of development of a simple multicellular organism and find that three components are necessary for the evolution of irreversible somatic differentiation: (i) costly cell differentiation, (ii) vegetative cells that significantly improve the organism's performance even if present in small numbers, and (iii) large enough organism size. Our findings demonstrate how an egalitarian development typical for loose cell colonies can evolve into germ-soma differentiation dominating metazoans.

Automated summary

The article discusses the emergence of irreversible somatic differentiation in complex animals, as well as the differences in cell differentiation and separation of reproductive tasks between primitive species and complex animals. The study found that costly cell differentiation, vegetative cells that can significantly improve organism performance even in small numbers, and large enough organism size are necessary components for the evolution of irreversible somatic differentiation.