Abstract
This first introductory lecture retraces the major historical stages in the concept of morphogenetic information, particularly in a mechanical framework of epigenesis where forms are elaborated progressively. This culminates in the concept of positional information, which determines the spatial coordinates of cells. The lecture is divided into two main parts, each devoted to one of the two general modes of information flow.
In the first time, we retrace the key stages of a long tradition which has seen the deployment of developmental information as the execution of a deterministic program, organized in a hierarchical and modular fashion, where genes control all cellular events in space and time. The concepts of master or selector genes, epigenetic landscape, cell lineage that models development as a decision tree, organizing center and morphogenes testify to this " programmatic " vision of developmental information.
Secondly , the lecture develops the concept of self-organization, which abandons any hierarchy in the flow of information, and any determinism : organized forms emerge from disorganized stochastic processes at a lower scale, without hierarchy, as seen in anthills or tree structures. Self-organization also implies the existence of numerous feedbacks.
The lecture concludes with a revised definition of morphogenetic information, whose nature is mechano-chemical and not just genetic, operating recursively at different scales.
