According to one influential tradition, to assert that p is to express a belief that p. Yet how do assertions provide strong evidence for belief? Philosophers have recently drawn on evolutionary biology to help explain the stability of assertive communication. Mitchell Green suggests that assertions are akin to biological handicaps. Peter Graham argues against the handicap view and instead claims that the norms of assertion are deterrents. Contra Graham, I argue that both mechanisms may play a role in assertive communication, although assertions as deterrents will often fail to provide strong evidence for belief.