But language has the potential to appear more or less universally interpretable (if you speak the language, that is), so we get the impression that it's non-individual, and thus individual speech differences become more obvious when we think about it, as you've been doing.

But the surprising part is that there's no way it can be non-individual. Everybody learns their language by imitating what people around them say, and figuring out how it all works. By themselves. People can help or hinder, but not really control, how children learn languages, and the result is that everybody learns their own languages, and then spends the rest of their life trying to pass as a speaker of the same languages as the people around them. With, of course, vastly varying degrees of success. The wonder is that we can understand one another at all, or at least convince ourselves that we do.

Some will say that language is in the DNA, but that's only because there's no place else they can think of. But even if that were true (and our current state of ignorance about molecular genetics is profound enough to keep us from disproving this hypothesis for a long time), it wouldn't explain how we manage to learn whatever languages are around us, nor how we sort out the individual differences and arrive at the belief that we're all speaking the same ones.

Simply amazing! This amazement is what's kept me interested as a linguist for half a century, and it seems unlikely to go away soon.

-John 

Lawler http://www.umich.edu/~jlawler 

"Bokonon invites us to sing along with him: 

'Horse got to run, bird got to fly, 

Man got to wonder, Why? Why? Why? 

Horse got to sleep, bird got to land, 

Man got to tell himself he understand.'" 

-- Kurt Vonnegut, "Cat's Cradle"