Looking for evidence of differentiation and cooperation : natural measures for the study of evolution of multicellularity

Electronic version of an article published as Advances in Complex Systems 12 (3) pp.255 - 271, 2009, DOI: 10.1142/S0219525909002222. Copyright World Scientific Publishing Company at : http://www.worldscinet.com/acs/ [Full text of this article is not available in the UHRA]The understanding of the evolutionary transitions is a major area of research in artificial life and in biology. We follow an artificial life approach to investigate these phenomena, using a system inspired by Anabaena cyanobacteria (which exhibit rudimentary multicellular differentiation and cooperation) in order to look for evidence of emerging differentiation and multicellular cooperation in colonies of individual cells. We first evolve single free-living cells with the help of a Genetic Algorithm (GA). These cells are controlled with genetic regulatory networks. The single cells are evolved to each perform both of two tasks: an abstraction of house-keeping metabolism and a reproductive cycle. Once such a cell was evolved with the GA, the cell is used to seed the growth of a multicellular filamentous colony, whose constituent cells continue to reproduce and evolve. Two types of colonies generated from the seed cell are studied: one with intercellular communication ability and one without. We introduce and apply new measures for assessing the impact of multicellular interaction on individual reproduction and on life span. The conclusion of these studies shows that the colony with the ability to communicate shows, with the help of our new measures, behaviors that hint at the emergence of early cooperation.Peer reviewe