This project focuses on innovations and mechanisms that facilitate evolutionary changes at the organismal level, in particular the constraining effects of internal selection, i.e., selection caused by characteristics of the developmental system. The main focus is on the conservation of the early organogenesis stage and on the conservation of adult traits that are determined during that stage, with the goal of understanding the interplay between genetic architecture, developmental mechanisms and stabilising selection. A first subproject on Evo-Devo largely concentrates on the role of internal selection as a conserving evolutionary force, using data available in the, immense but currently rather neglected, older literature for the anatomical basis, and a variety of datasets obtained from elsewhere for inferring selective pressures. These datasets are obtained through the internet, gleaned from e.g. the farmacological literature, or obtained through collaborations with various medical and veterinary research groups. A collaborative experimental program is going on with the Pathology department of the VUMC (Free University Medical Center). In this collaboration we study the internal selection against mutations affecting the highly conserved embryonic neurula stage and the number of cervical vertebrae and digits (determined during this stage). This internal selection is due to pleiotropic effects: multiple congenital abnormalities, including importantly cardiovascular and bleeding abnormalities and childhood cancers. We have deduced from the literature which developmental mechanisms are probably underlying the pleiotropic effects. By determining the specific pleiotropic effects (pathology associations) we are testing our hypothesis on the underlying mechanisms. Furthermore, the importance of internal selection against highly conserved traits (number of cervical vertebrae and digits) is compared to that against variations in less conserved traits (e.g. lumbar vertebral number). Conserved traits are expected to be indicators of medical risks. All this is done against the theory of high dimensional fitness landscapes, studied in projects 3 and 4, and the methodological principles studied in project 5, as a backdrop. A second subproject concerns the role of phenotypic plasticity and genetic assimilation in the process of adaptation and evolutionary change of cichlid fishes in collaboration with Lauren Chapman of McGill University and Thomas DeWit of the Texas A & M University. A third subproject is on the intra-specific relationship between size and longevity in dogs in collaboration with Tom van Dooren and Inke van der Sluijs of the Animal Ecology section and with Marc Nussbaumer of the Natural History Museum in Berne.