Cbc: This caught my attention also in shag's first post, and for essentially the same reasons Michael gives here: Origins and/or evolution of language is not a topic that belongs to any systematic study. One can study the evolution (though that is not really the right word) of English _beginning_ with Old English. Comparative linguistics can study t he evolution (still not really the right word) of (some) language groups (indo-european; afrio-semitic, etc.), but the evolution of language is a matter of personal speculation, not study.
The speculation, however, need not be a sociobiological specualtion: two of the more interesting speculations, one 60 years ago and one in the present decade, are not. The first is that of Susanne Langer, who in Philosophy in a New Key, suggested that language emerged from ritual. The other, by Ian Tattersall, is that it was invented by children playing, probably several times before adults picked it up and developed it for more 'practical' purposes. (Langer does knock down, I think deciseively, the assumption that language developed for practical purposes. After all, right up the to present day the most important functions of language are phatic.) Both speculations are independent from, or rather in absolute opposition to, any sociobiolgoical explanation, for both assume that the _capacity_ for language evolved long before language itself appeared. Ldanguage had nothing whatever to do with the evolution of homo sapeiens but ws invented/developed by biologically modern humans - probably 10s of thousands of years after the emergence of that species. Language is what Gould & Lewontin call a [forget the term - and magnification does not help scanning an index.]
But does shag mean by the "evolution of language" what has happened _subsequent_ to its full emergence. That, as I indicated above, is a question capable, to a point, of systematic study. Looking forward to clarification.
Carrol