[rquantz]

What an excellent idea. My first thought was that it must have something to do with speech or expression – maybe having a protruding bone bobbing up and down somehow makes speech more comprehensible? The idea of it contributing to facial expressions seem more likely though. Hopefully someone here will take up this line of inquiry.

[dalke]

The article mentions that hypothesis:

> Others have suggested that the chin is an adaptation for chinwags: It resists the forces we create when speaking. After all, speech is certainly a feature that separates us from other living animals. But there's no good evidence that the tongue exerts substantial enough forces to warrant a thick chunk of reinforcing bone. “And any mammal that also communicates vocally or suckles or engages in complex feeding behaviors that involve the tongue are probably experiencing similar stresses and strains, and they're not getting chins,” says Pampush.

Nor should we think that extra structure for complex sounds are needed for a language or comprehensibility. Consider the Silbo Gomero Language, which is "a whistled form of a dialect of Spanish." It "has only 2 vowels and 4 consonants, according to the official nomination document submitted during the UNESCO convention." (Quotes from Wikipedia.)

Verbalized Morse code is another example of how simple vocalizations are all that are needed for a comprehensible language.

[vorg]

> Nor should we think that extra structure for complex sounds are needed for a language or comprehensibility

A language which evolved from an earlier language, e.g. Italian, or is based on another language, e.g. Silbo Gomero, doesn't need complex sounds to get started, and often replaces "words" in the source language with rules, i.e. replaces lexical and phonological complexity with inflectional and grammatical complexity. But perhaps the very first language to ever be invented will rely on many different sounds and on many different words made from those sounds, but have a simple grammar. A recent study showed the likely dispersal of language from an initial point somewhere in Africa by counting the phonemic diversity, i.e. number of different speech sounds, in various languages around the world. [1] Perhaps the very first language had over a hundred different sounds to compensate for lack of grammar rules.

Perhaps a chin is needed to speak that very first language. Perhaps it had far more clicks than Khoisan, as well as the usual array of consonants, vowels, and tones. Maybe a chin helps with many of the clicking-like sounds.

[1] http://archive.cosmosmagazine.com/news/human-language-spread...

[dalke]

What does "the very first language to ever be invented" mean?

We know that other primates communicate with each other. This form of communication includes different sorts of warning calls, and perhaps also vocalizations for identification.

Any human language would have developed from a similar sort of proto-language, without an a-ha moment when two humans finally invented the language. (And if there was such a moment, then the chin would have had to evolve first, for some other reason.)

Therefore, I don't think it makes much sense to say "very first language" or "invented."

Let's suppose it's meaningful to talk about the first truly human language. In that case, the population of the original speakers would be small. According to the paper you gave, "phoneme number decreases as a population gets smaller." Thus, it would suggest the first language had a low phoneme count.

The problem is, that guideline isn't useful for the timescale we're talking about. It's believed there was a genetic bottleneck some 50,000 to 100,000 years ago (see https://en.wikipedia.org/wiki/Population_bottleneck#Humans ). All living humans come from a relatively small and relatively recent population, which means all of the diverse languages of Africa come from an originally quite small population, which therefore would have had a lower phoneme number.

Thus, on the flip side, what happens when populations get larger and isolated? Proto-Indo-European shows that it only takes a few thousand years to develop German and Celtic from the same language, and we know modern language can have sounds that weren't in the parent languages.

So while the principle might be useful for migrations within the last 10,000 years, that's still quite recent in the evolution of humans.