ABSTRACT
Evo-devo, the study of the evidence from development that illuminates evolution is essentially the study of how homologous proteins, functioning either alone or in networks, have similar roles in sometimes very dierent embryos. is was not an obvious expectation; even the idea seemed inconceivable before the molecular basis of regulatory control mechanisms in eukaryotes began to be understood, late in the last century. ere was thus no reason to suppose that there should be any similarity in the means of producing functionally similar, but morphologically dierent, organs, such as, for example, the eyes of vertebrates, mollusks, and arthropods. It was in this context that Salvini-Plawen and Mayr (1977) suggested that eyes had separately evolved some 40 times across the phyla; they would certainly never have predicted that a single gene, Pax6, had a key role in the development of each.
