Don Ringe has a new post at the Log (a followup to the one I posted about here) in which, in answer to a question by David Marjanović, he discusses in detail the histories of the IE words for ‘wheel’ (PIE *kwékwlo-s, collective *kwekwlé-h2) and ‘horse’ (PIE *éḱwos). He starts off with a general discussion of the issues involved that should be accessible to anyone; here’s a sample:
Nonspecialists sometimes think of languages, including reconstructed languages, as sets of words; but that’s somewhat less than half true. Yes, every language does have a distinctive lexicon, but the structure of the language is even more distinctive; you can replace a large proportion of the lexicon with words borrowed from other languages without any significant effect on the language’s structure. (Modern English is an obvious example.) Historical linguists reconstruct a protolanguage’s system of sounds and system of inflectional morphology as well as its lexicon. In some cases the sound system and inflectional system turn out to be complex and intricate, and PIE happens to be one of those cases. Moreover, because we reconstruct protolanguages by exploiting the regularity of sound change, competent reconstructions are mathematically precise. Under those circumstances, when we reconstruct a word which fits perfectly into the sound system and inflectional system, with no hint that there is anything out of line, the default hypothesis has to be that it’s an inherited word, simply because the odds that a word borrowed from some other language would fit in well are significantly lower.
He goes on to a detailed analysis of the two words in question, which may be tough sledding for someone with no background in the subject but which gripped me like a good detective story. But this paragraph from his conclusion shouldn’t present problems and is of great theoretical interest:
This raises a methodological point that we can no longer avoid. Is there any difference between a word which is reconstructable for a protolanguage and a word which spread from dialect to dialect of the protolanguage as it was breaking up? As usual, it depends on the individual case. If the real-world separation of the daughters was genuinely abrupt—that is, one group picked up and moved within a generation or so, and subsequent contacts were infrequent and brief—then there is a clear difference between the two scenarios. But most disintegrations of speech communities don’t happen like that; dialects remain in contact as they diverge, continuing to trade linguistic material until some event finally makes them lose touch altogether. (The best discussion of these processes is Ross 1997.) In such cases the “protolanguage” which we reconstruct is most unlikely to correspond to a single, completely uniform dialect that existed in the real world before its speaking population became large enough to exhibit significant linguistic diversity; it almost inevitably corresponds to a dialectally diversified speech community, still unified but no longer uniform, simply because we can’t tell the difference between words and grammatical forms which had been in the language for generations and those which had arrived very recently. It is also likely that our reconstruction will be temporally “out of focus”, including some inherited words and forms which were no longer characteristic of all the dialects and some new words and forms which were still spreading from dialect to dialect. There are good reasons to suspect that our reconstruction of PIE is like that.
Don promises at least one further posting, and I hope there will be many more.