The 2008-2009 lecture focused on the evolution of the nervous system. It began with theoretical considerations on the concepts of robustness and plasticity. Naturally, questions of evolution were linked to those of development from an Evo/Devo perspective. We introduced the notion of evolvability, defined as the ability to respond to a change in the environment by creating new forms (in the broadest sense) with a selective advantage.
We discussed the hypothesis that there are neutral zones in the "genotype-to-phenotype" landscape within which mutations do not modify the phenotype. These neutral spaces, synonymous with robustness, increase evolvability by enabling unconstrained navigation within this "landscape" and approaching regions that can allow sometimes abrupt transitions. If such shifts were not possible, then the system would be too constrained to leave a zone of strong adaptation.
To illustrate the importance of epigenetic phenomena, we have introduced heat shock proteins and described, in Drosophila and fish, how their pharmacological inhibition can reveal underlying phenotypes, with, in Drosophila, the possibility of the revealed phenotype remaining fixed for several generations, even after the pharmacological inhibitor has been withdrawn.
