Some bird species are capable of communicating in proto-language that is only a few steps removed from full language capability in the human sense, so I think t

Some bird species are capable of communicating in proto-language that is only a few steps removed from full language capability in the human sense, so I think the most likely answer is "accident of evolution". If the primates didn't take over the Earth, maybe evolved parrots would have, given a few more million years.