Our ability to map sound into pronunciation--vocal imitation--is necessary for vocabulary learning, and so the existence of language. It is also unexplained. Here I show that speech is imitable due because of the brain's use of the innate sensitivities of the vertebrate auditory system for speech motor targets. Their public nature enables speech to transmit articulation information. These units I suggest closely link with phones, the minimal unit of speech segmentation. The conjecture that phones function as a replicative code removes five unexplained anomalies in language science: (i) why nearly eight hundred phones exist but any language uses only a tiny subset of them (evolutionarily this makes no sense); (ii) why newborn infants hear phones of all languages; (iii) why animals also hear them; (iv) why the Wernicke's and Broca's areas arose from homologous areas in primates which process imitation, and why (v) in humans these areas process nonspeech imitation.