This chapter considers two competing views about what modularity might consist of, which the authors refer to as sui generis modularity and descent-with-modification modularity. Descent-with-modification helps make sense of the considerable phylogenetic continuity that has been documented in recent years, in terms of comparative psychology, comparative neuroanatomy, and comparative genomics. The chapter also considers language, the canonical putative module, and its relation to cognitive systems. Cognitive mechanisms for spatial and temporal representation seem to run deeply through the structure of the linguistic system. The notion of descent-with-modification, once recognized, has significant implications for how one can assesses debates about modularity. The descent-with-modification perspective suggests caution for inferring the absence of modularity from many studies of "normal" cognition. Descent-with-modification also suggests that one should expect the hallmarks of ancestry even in the very machinery that makes abstract linguistic representation possible.