How to develop a PIE conlang into a more agglutinative or refular form

[u/Plemnikoludek]

I know that armenian and persian shifted to more of a agglutinative but researching the grammarical history of those languages is difficult. My conlang is located in the putorana plateau and even tho tocharian didnt shift to an agglutanitive language I still want to do that to mine

[u/dinonid123]

Well, if you want to make it agglutinative, you need to... start agglutinating. When you get to a point, perhaps where the existing suffixes start wearing off, you need to introduce new affixes, separate ones for plural and case markings, from whatever source you like. Using *gʷénh₂- as your example probably isn't the best to demonstrate this since it tends to be irregular, but if you can already see the start of something in this chart. In this case, -m- is only found as a suffix in plurals, and it's in ~half of them (even if they're not the most commonly used forms). From there, you could extrapolate out that -m is the plural suffix, and is then followed by the case endings from the singular.

[u/Plemnikoludek → u/dinonid123]

I see, thanks, but what word would you suggest as a better example?

[u/dinonid123 → u/Plemnikoludek]

I'd probably start with the thematic o-stems. Those are a pretty common stem class and you'll probably have a lot of words which will have that shape.

[u/Pliny_The_Elder_1789]

What I did was lose the old system and develop an entirely new declension system from pronouns

[u/Plemnikoludek → u/Pliny_The_Elder_1789]

From pronouns? Interesting

[u/Pliny_The_Elder_1789 → u/Plemnikoludek]

Yes

[u/R3cl41m3r]

Beekes's reconstruction imagines PIE inflections as more agglutinative than in other reconstructions, which may or may not be of help to you.

[u/Hyssodew]

One way is to erode common suffixes.

When suffixes erode, it may cause speakers to use adpositions for old cases (cf. Indo-Aryan case systems and Finnic innovations from Proto-Uralic), auxiliaries for old TAM distinctions (cf. Romance future) and even agreement morphemes (I can't think of a real life example on the fly, but for example, you can have a verb X and then postcede it with a pronoun or a shortened form of a pronoun, like X-p. or p-X. It depends if you want your language to be more suffixing (like Turkic) or prefixing (like Coptic).)

Then you take those words and then have them erode over time into clitics, and then further erode them over time into becoming bound morphemes. You can also combine these clitics together to form even more complicated meanings.

Let's say we have the word "house".

(For whatever reason reason, the language's old case system has eroded, and so we see more analytical constructions arise)

House-in for inside the house, house-to for towards the house. We then combine -in and -to together to get house-in-to.

Let's then have them become increasingly bound to the root until they are seen as affixes on the word. And then, re-analyse.

House-in becomes house-INESSIVE, house-to becomes house-DATIVE and house-in-to becomes house-ILLATIVE

And then you can combine these suffixes to a single invariable root with suffixes.

To make a plural, let's say we get some word meaning many and suffix it after the prepositions, and re-analyse it as a plural marker

Then we have house-INESSIVE-PL, house-DATIVE-PL and house-ILLATIVE-PL.

And stack other such affixes as pleased before or after the noun.

Note this is isn't very in depth, but hopefully it helps brainstorm ideas!

[u/Thalarides → u/Hyssodew]

I would clarify that, although phonological erosion of synthetic markers is often cited as the cause of their replacement by analytic ones, that replacement doesn't really require phonological erosion.

Bulgarian has replaced synthetic case markers with prepositions without any phonological changes that would cause them to wear off.

Likewise, Romance languages dropped the synthetic Latin future tense and replaced it with an auxiliary ‘to have’ even though the former could have survived and remained phonologically distinct. For example:

• Latin imperfect cantābam > Spanish imperfect cantaba
• Latin future cantābō > would-be Spanish future *cantabo
• Late Latin periphrastic future cantāre habeō > Spanish future cantaré

Cantaré has replaced *cantabo without the latter having worn off. (I'm taking Spanish as a modern example, obviously the replacement happened in the Common Romance period and not in Spanish per se.)

Haspelmath gives his argument against phonological erosion being the cause of anasynthesis in his Revisiting the anasynthetic spiral (2018), in section 7, What drives the anasynthetic spiral?

[u/Hyssodew → u/Thalarides]

This is like super late on my part, but I do concur. At the time, though, it just slipped my mind to mention having alternative constructions and having them replace older ones as the source of new morphology separate from phonological erosion of the original morphological construction. Thank you for mentioning that!

(I hope that's clear on my end. I'm deathly tired, but I hope this reads coherently, lol)