The question is not, "can they talk"?

An argument for denying moral rights to nonhuman species is that beliefs, desires, and interests are inherent in the normal human capacity for speech and, since only humans are linguistically capable, only humans can have rights. We argue that linguistics and many conceptual abilities are ontogenetically independent in humans and that various morally relevant mental capacities can exist independently. We also then argue that phylogenetic independence is also possible and hence, that the concept of an inherent dependence of moral standing on having linguistic capabilities is insufficient for denying rights to nonhumans.