The affordances of civilization are founded on informational and mechanical extensions of human perception and action. In the natural world such extensions are not that unusual. Richard Dawkins coined the term “extended phenotype” to describe situations in which gene sequences project their effects beyond the animal to which they belong. For example, the alarm calls of vervet monkeys describe affordances, perceptions of threats coupled to specific evasive behaviors. However, they are confined to the local spatial and temporal context. To describe affordances that may be distant in time or space, or subject to uncertainty, sequences incorporate a grammar of extension. The here-and-now-and-must can become the there-and-then-and-might. In human language, the grammar of extension depends on prepositions such as over, under, between, beyond, etc., deictic (pointing) words like this, that, here, there, etc., and modals that express probabilities, like will, could, and might. New nouns and verbs can be coined freely; they are an open class. Prepositions, deictics, and modals form a closed class; we cannot coin new members. In the cell, sequences of DNA also contain closed and open classes, open being exons that are expressed and closed being short, conserved marker sequences that govern gene expression and alternative splicing.