Abstract: While non-human apes have quite sophisticated forms of communication, exchanges between humans display a variety that is unsurpassed by any other species. How did that variety get underway? Starting with chimp-style communication as my baseline and target set of basic human-style exchange types I derive the following partial order:

1. Requestives (“Please do the dishes!”) ; Cohortatives (“Let’s do the dishes!”)

2. Permissives(“You may do the dishes”) ;  Promissives (“I’ll do the dishes.”)

3.Declaratives (“I did the dishes.”)

Cohortatives may or may not be viewed as a sub-category of requests, but either way, I argue that they merit more attention than they have received so far, especially in an evolutionary context. In the proposed model, cohortatives and requests evolved first, followed by promises and permission giving; declaratives evolved out of promises.