What do we know about the origin of the ablaut series as a tense marker in Germanic (or any other) languages?

a look at OneLook took me to the Wikipedia, which had this:

Ablaut

From Wikipedia, the free encyclopedia.

In linguistics, the process of ablaut (from German ab-: off + laut: sound) is a vowel change accompanying a change in grammatic function. For example, the vowel change in English from i to a to u in sing (present tense), sang (preterite), sung (past-participle) is referred to as an ablaut.

Verbs that display ablaut in English, and that do not form their preterites with a dental suffix like -ed or added -t or d, are called strong verbs. There used to be several regular classes of strong verbs in English, and many more of them; virtually all monosyllable verbs were strong verbs in Old English. Now, there are fewer of them; the force of analogy has remade many of them in the image of weak verbs, those verbs that form the preterite with a dental suffix. Sound changes like the Great Vowel Shift have also obscured some of the underlying regularity of the former classes of strong verbs. Now most of them are considered irregular verbs.

Ablaut is a common characteristic of many Indo-European languages and is also known as gradation. Latin displays ablaut in verbs such as ago (present tense), "I drive"; egi, (perfect tense), "I drove." Ablaut is a semi-regular phenomenon that affects whole classes of verbs in Ancient Greek and Sanskrit.

Indo-European had a characteristic general ablaut sequence that contrasted the vowel phonemes o/e/ə/Ø through the same root. Most philologists believe that the presence of laryngeals in the Indo-European roots, and their subsequent loss in most daughter languages, led to the development of several parallel ablaut sequences in Indo-European and its daughter languages.(e.a.) When ablaut is a regular feature of a language's grammar, it is often called vowel gradation.

The ablaut is distinguished from the phonetic influence of a succeeding vowel, called umlaut.

See also: reduplication; augment

http://en.wikipedia.org/wiki/Ablaut

here's Wikipedia on laryngeals:

http://en.wikipedia.org/wiki/Laryngeal_theory
neat stuff. wish I had more time today to look it over...

another interesting site, at least to me.
http://www.tundria.com/Linguistics/IEPhonol.htm

It seems that the sound change came first and then the grammatical reanalysis. This is a process called grammaticalization and is much studied. Laryngeals are interestesting because they were posited by Saussure for the proto-language even though none of the daugther languages displayed them. Then along came Hittite, and it had an example of one laryngeal surviving. Though, Hittite may have been a sister language of PIE. Your mileage may vary.

Thanks, cygne. I never think to look at wikipedia.

Thanks, Nuncle. You're saying that it's lost in the mists of time?

S'pose so. I've heard ablaut ascribed to a change in stress / tone in PIE words which why you have a bunch of e ~ o ~ null phonemes in some linguists' reconstructions of PIE phonology. OTOH, umlaut (a sibling process) is common enough in languages the world over, and (who knows) may be related to vowel harmony ...

vowel harmony

ooh, tell us more!

Turkish and Finnish have it. The way it works in those languages is that there are X groups of vowels and endings have to match their vowel(s) with the vowels in the root / word they're attached to. Keeps things harmonious.

http://en.wikipedia.org/wiki/Vowel_harmony

thanks, jheem, I never knew anything like that existed. cool.

You're welcome. Ain't language wunnerful?

It seems that the sound change came first and then the grammatical reanalysis. This is a process called grammaticalization

Jheem, doesn't grammaticalisation refer to only a change in the *meaning of a word, specifically when, it transforms in from something concrete and tangible to one with mere grammatical connotations? I am trying to think of an example, but am struggling with one.
I imagined that the word doesn't morph in either spelling or pronunciation, its meaning however undergoes a specific change.

<i>doesn't grammaticalisation refer to only a change in the *meaning of a word, specifically when, it transforms in from something concrete and tangible to one with mere grammatical connotations? I am trying to think of an example, but am struggling with one.</i>

But that's kinda what I meant. The ablaut went from being a purely phonological phenomenon (that happened in other environments) to being one that was reanalyzed as being morphological. Some weak verbs in English have been reanalyzed as strong ones of the ablaut-series. This is slightly different from your definition, because it doesn't have to be words, but can be morphemes.

<i>I imagined that the word doesn't morph in either spelling or pronunciation, its meaning however undergoes a specific change.</i>

Not necessarily. One classic example of grammaticalization is howe the modern Greek future morpheme, <i>tha</i> developed out of <i>thelo ina</i> 'I wish that'.

Maahey, would an example of what you're thinking of be the combination of 'by' and 'cause' into the conjunction because?

Bingley

Thanks Jheem. Bingley, I am rather uncertain of this, since I read it all a good while ago, but, the example that keeps coming back to mind is, 'has'. The spelling/ pronunciation is unaltered, but the word itself has gone from meaning, possession of something to, a verb qualifier in the past tense.

Bingley has the book.
Bingley has scored a goal.

Whilst re-reading my earlier post, 'since' caught my eye. Is this also a case of grammaticalization? (at least as I have understood it)

Liz was married last year; she has since changed her name
Harry keeps forgetting the details, since it all happened so long ago.

Which usage came first?

I think that since as because is later in meaning. Or did you mean one is an adverb and the other a conjunction? I'll see if I can round up a couple of good examples. (There's a good book by CUP on Grammaticalization.)

I categorically deny that Bingley has ever scored a goal in his life.

Bingley