 Onomatopoeia (and mimesis more broadly) may be seen as a kind of iconicity, though even onomatopoeic sounds have a large degree of arbitrariness.Derek Bickerton has posited that iconic signs, both verbal and gestural, were crucial in the evolution of human language.Animal communication systems, Bickerton has argued, are largely composed of indexical (and, occasionally, iconic) signs, whereas in human language, "most words are symbolic, and ... without symbolic words we couldn’t have language".