In their considered reviews both Thomas Pradeu and Lindell Bromham introduce important topics not sufficiently covered in our book. Pradeu asks us to enlarge on the epigenetic and ecological context of genes, particularly in the form of symbioses. We use the relationship between eukaryotes and their symbiotic organisms as a welcome opportunity to clarify our concept of the developmental niche, and its relationship to the developmental system. Bromham’s comments reveal that she is primarily interested in identifying macroevolutionary patterns. From her vantage point eco-evo-devo, the study of phenotypic plasticity, epigenetic and exogenetic inheritance, have not yet demonstrated the need for any revolutionary change in evolutionary thought. For us they highlight the extent to which proximate developmental mechanisms can inform ultimate biology.