The Piranhã  are an Amazonian tribe in Brazil, that simple refuse anything foreign, and speak a weird birdsong-like language, experts are baffled, even questions like if they are retarded arise, of course that can't be it, after all they are human and therefore the basic elements that make human speech different from other animals have to be there, they just have to, they can't find them but they know they are there, or at least another reasonable explanation exists. :rolleyes: