The emergence of multicellular organisms 600 million years ago represents a major challenge for biologists. Scientists at the Complex Systems Laboratory , group of the Department of Experimental Sciences and Health (DCEXS) of the UPF and the Institute of Evolutionary Biology (CSIC-UPF), study sufficient conditions to evolve virtual multicellular organisms from cells of reduced complexity. The results are published in the Journal of the Royal Society Interface.

Different lineages of multicellular creatures have appeared throughout evolution. Multicellularity provides several benefits: protection from predators, cooperation rather than competition when foraging ... For this reason, natural selection has benefited multicellularity to the wide diversity that is part of our current biosphere. However, groups of cooperators are normally exposed to defectors: cells that get the benefits of participating in the group without providing the associated costs. A key example in our bodies defectors are tumors: cell lines in which the interests of the cell have been put ahead of the interests of the organism. The danger of these dynamics is obviously the death of the organism. To keep uncooperative mutants at bay, multicellular systems must develop mechanisms to discriminate between self and others, a multicellular identity.

The scientific team led by Ricard Solé, ICREA researcher and head of the Complex Systems Laboratory of UPF, has studied the conditions that promote the creation of a multicellular organism capable of generating an identity mechanism and thus prevent the defectors. The authors of the study observed the evolution of cell populations located in the same environment containing limited nutrients and toxic substances. In these populations, they observed the selection of characteristics of a primitive multicellular organism (or protoorganismo): differentiation, development of robust structures and the emergence of a collective fitness.

"Many of the multicellular organisms of nowadays display intricate spatial patterns implemented by developmental programs, which are tightly controlled by genetic networks", comment the authors. "But an early stage might have involved physical aggregation phenomena that could have given rise to some class of cooperating multicellular assemblies". This implies the existence of a wide range of possible multicellular entities located between what is known as simple cell aggregates and complex multicellular organisms with development programs.

Reference Article: Duran-Nebreda, S.; Bonforti, A.; Montáñez, R.; Valverde, S.; and Solé, R. (2016). Emergence of proto-organisms from bistable stochastic differentiation and adhesion . Journal of the Royal Society Interface DOI: 10.1098/rsif.2016.0108