Might languages have developed hard-to-pronounce sounds to mark outsiders? Mark Pagel, professor of evolutionary biology in Reading thinks that the answer to this question is “almost certainly yes”.
“We don’t even have to assert that this happened deliberately; it could just be that by stumbling upon these difficult-to-pronounce sounds, ancient tribal groups came to recognize that they could profitably identify “insiders” and “outsiders.” One of the best examples of this is the “click” sound of the San Bushmen’s and the Hadza languages of Africa. If you don’t learn to make this sound in your youth, you can never properly make it, and so this sound, among other uses for it, can reliably identify outsiders.”
Sounds cannot be faked
“The ability to identify outsiders has been important throughout our history because our tribal groups have been of enormous value to us in promoting our survival and prosperity. They have also been in an almost continual state of conflict with other groups competing over the same lands and resources.”
“As a result, tribal groups developed a variety of ways of promoting tribal cohesion and identity, and language is perhaps the most salient of these. The significance of difficult-to-pronounce sounds is that they genuinely mark out someone who can make them as someone with whom you share a long cultural history. So, in this sense, they cannot be ‘faked’, and this is why they become trustworthy or reliable ‘badges’ of identity.”