Not sure all the pieces of an explanation are present here... What does the "connection from the brain's central processing *back* to the auditory processing pathway" do exactly? It's hard to imagine what thoughts sound like before language, insofar as those thoughts are not already auditory contents. And what is it's relation to the eventual emerge of language? A necessary condition only? Or was it sufficient?

I'm surprised this part is puzzling, since it is such an intimate part of human experience. The connection enables us to "play sounds in our heads". That we "play" sounds indicates they originate in central processing. That we play "sounds" indicates that they partake of the same neural machinery external sounds do.

Try the following exercises, which test the strength of the different perceptual feedback loops of this kind. I don't claim my results are universal, so ymmv.

Imagine the sound of wind chimes.
Easy. I can do this with seeming perfect fidelity.

Imagine a rose
A wispy, unstable thing. I'm sure many can do better than me here.

Imagine the taste of mint
I immediately visualize a sprig of mint. I'm not sure I can do this at all.

Imagine the smell of coffee
I visualize a cup of coffee. Not sure I can do this either

Imagine the feel of sandpaper
I visualize the sandpaper, in one of those tools. This one seems otherwise inconceivable.

According to my theory it is no accident that the auditory feedback loop is by far the most developed.

It's hard to imagine what thoughts sound like before language, insofar as those thoughts are not already auditory content — Welkin Rogue

Prior to language I would call these proto-thoughts. Strings of the noises that the animal makes in the world, noises which have innate, instictive meaning, played in the head. My intuition tells me that this ability enabled a greater communicative complexity, without yet arriving at language. Via rumination, play with onself and others, and expanded cultural transmission. But I haven't worked out the details.

Okay sure so we've got the ability to play sounds just like we're hearing them. How does this lead to language acquisition? It seems like there are many possible forms of language, but that this neurological development inclined us towards a verbal form, though it hardly explains the emergence of language itself (it might be a necessary condition for a certain form of language). I'm not ruling out a deeper connection... your second post indicates that this is where you are focusing now. If I think of anything further useful to contribute I'll post.

I enjoyed your mental exercises. I think I can do pretty well in simulating visual images, tastes and textures. I've never been good with smells.

I think I have a comprehensive theory of how human language was naturally selected, but rather than try to summarize in a brief post, I'll provide links to a couple chapters I wrote on the subject, located at philosophyofhumanism.com . This will give some good insight into how language evolved if you want to trouble reading it.

Phylogenetic Factors and Evolutionary Origins of Humanity's Language and Conception
The Evolution from Precivilized to Civilized Human Conception

Because it's not just playing sound, it's thinking! Proto-thinking, because it is prelinguistic, but thinking still. What more natural thing for an animal to subvocalize than what they vocalize? Once a cohort starts thinking, it is a natural conclusion that their communicative scope increases. For my theory to work it needs only to increase in scope enough so that "sophisticated" seduction becomes possible, meaning that it relies on verbal virtuosity.

I don't understand your objection that this development inclines us towards a verbal firm of language. All natural language is verbal. If the visual pathway has developed first we might all be signing.

We know we can think, and we know we have verbal language. I think the strength of my theory is that thinking is actually the simple part and so came first, and it plausibly suggests how language arose subsequent to thinking.

One necessary condition is that there be a sufficient richness of vocalizations already present for thinking to be able to do anything at all. Otherwise as you say it would just be playing sounds in the head to no effect.

One necessary condition is that there be a sufficient richness of vocalizations already present for thinking to be able to do anything at all. Otherwise as you say it would just be playing sounds in the head to no effect. — hypericin

Ok I'm starting to see the idea more clearly now. So is the thought that the crucial auditory simulations that this neurological development facilitated were simulations of the organism's own vocalisations? Prior to language, these vocalisations would have been, I guess, various emotive vocalisations. I'm no anthropologist or primatologist, so I can only consult my cartoonish intuition about what these might have been like - an intuition tutored by my culture in various peculiar (non-universal) ways, no doubt. I am thinking of: gasping when surprised, yelling or roaring when angry, crying and whimpering sounds when sad, sighing when contented, laughing sounds when amused, moaning when experiencing pleasure, and so forth.

Then is the idea that we use these resources to develop a proto-language - that these subvocalisations (auditory simulations of vocalisations) begin to increase in complexity and eventually stand as 'signs' with something like semantic content which we can manipulate into strings (sentences)? This makes it sounds like a private language. But I don't think that's what you have in mind, is it? The development of this increasingly complex subvocalisation must be informed by social and cooperative processes, as everyone is going through the same developmental process.

The next part of your theory is that the increasing complexity eventually leading to full-blown language is fuelled by sexual selection. Maybe that's true. I don't know.

I'd still like to hear more about what advantage the auditory connection (auditory simulation ability) conferred, if any. Is it to do with increasing the richness of our imaginative capacities, and hence improving our learning from the past and planning for the future? Of course, it may have been due to other evolutionary processes, but we all like an explanation in terms of adaptation.

So is the thought that the crucial auditory simulations that this neurological development facilitated were simulations of the organism's own vocalisations? — Welkin Rogue

Right

Prior to language, these vocalisations would have been, I guess, various emotive vocalisations. — Welkin Rogue

If you think about it, many modern words which can stand alone as a sentence could have served as primitive vocalizations: hmm. wow! huh. huh? awwww. yes! no!

The development of this increasingly complex subvocalisation must be informed by social and cooperative processes, as everyone is going through the same developmental process. — Welkin Rogue

Right. Before this neuroevolutionary event, there was only public "language". After it, there is public and private "language", each informing and contributing to the other, in a cycle. Individual innovations could e transmitted to the group, who would transmit their collective innovations to other groups, and to the next generation. I believe the expressive limit of prelinguistic vocalizations would be quickly reached.

but we all like an explanation in terms of adaptation. — Welkin Rogue

I think the key immediate benefit is improved general cognition, without spending too much neurally. Something like what we do with the visual feedback loop. At least for me, the visual loop is not nearly as developed as the auditory. It is non-linguistic. And yet, it is indispensable for thinking, if it were to disappear (as it does sometimes when I am under a lot of stress) I would be mentally crippled.

And even though I am linguistic and so I predominantly use the auditory loop for saying words to myself, I sometimes use it to think in other ways, for instance musically. Sometimes music will accompany my visual thinking, in such a way that the "logic" of the music is somehow analogous to the logic of the problem. There is more utility to playing sounds to yourself than words.

This advantage gives the trait breathing room before the point is reached when a female be seduced with savvy vocalizations. As soon as this is possible, vocal flexibility, linguistic ability, and general brain power along with it, explode like an atom bomb.