We present a model of parallel co-evolution of development and motion control in soft-bodied, multicellular animats without neural networks. Development is guided by an artificial gene regulatory network (GRN), with real-valued expression levels, contained in every cell. Embryos develop within a simulated physics environment and are converted into animat structures by connecting neighboring cells through elastic springs. Outer cells, which form the external envelope, are affected by drag forces in a fluid-like environment. Both the developmental program and locomotion controller are encoded into a single genomic sequence, which consists of regulatory regions and genes expressed into transcription factors and morphogens. We apply a genetic algorithm to evolve individuals able to swim in the simulated fluid, where the fitness depends on distance traveled during the evaluation phase. We obtain various emergent morphologies and types of locomotion, some of them showing the use of rudimentary appendages. An analysis of the selected evolved controllers is provided.
2. Figure 4 - example of evolved morphologies and
The figure demonstrates a sample of obtained morphologies and locomotion types in the system. Note that the individuals were evolved only for their ability to move in a fluid. Neither their morphology nor the type of controller were externally enforced. Each individual develops from a single cell into its final morphology and each cell is controlled (both during developmental stage and locomotion stage) by activity of its gene regulatory network encoded in linear genome.
Fig. 4a The turtle strategy, an example of the use of appendages
Fig. 4b The shark strategy: the use of a tail fin for propelling
Fig. 4c The worm strategy: propelling with undulatory movements
Fig. 4d The jellyfish strategy: an exploitation of asymmetric contraction and expansion speed combined with one blunt end (contractions are faster than expansions)
Joachimczak, M., Kowaliw, T., Doursat, R., and Wróbel, B. (2012). Brainless bodies: Controlling the development and behavior of multicellular animats by gene regulation and diffusive signals. In Adami, C., Bryson, D. M., Ofria, C., and Pennock, R. T., editors, Artificial Life XIII: Proceedings of the Thirteenth International Conference on the Simulation and Synthesis of Living Systems, pages 349-356, Cambridge, MA. MIT Press. PDF / BibTeX / RIS / CiteULike
4. Related work on the system
Have a look at our first paper, in which cells were controlled by sine oscillators: