Topic markers and adpositions

[Benturi]

Are topic particles generally derived from adpositions? I don't know many languages that have a specific topic marker (Japanese, Korean, Kawésqar...); but all of them are head-final, postpositional languages and the topic marker also follows the topic. And then there are prepositional languages like English, German or Spanish, where one can optionally mark the topic with a preposition or prepositional phrase like "as to", "bezüglich", "en cuanto a". Is there any postpositional language with a topic marker that precedes the topic, or viceversa? If a topic marker were derived from a relative clause, a participle or an adjective, then it would be on the opposite side of the adpositions, isn't it? Something like (in a head-initial language):
X of-which-we-speak > X TOP
X spoken-of > X TOP

[zompist]

Quechua -qa presumably didn't derive from adpositions, because the language has none.

[Miekko]

Quechua -qa presumably didn't derive from adpositions, because the language has none.

Where do Quechua suffixes originate from?

[Benturi]

I don't know the specific case of Quechua, but I think case affixes usually originate from adpositions and ultimately from adverbs, nouns or verbs as the head of the construction. In any case, Quechua -qa attaches enclitically to the topic and is thus "on the same side" of the case suffixes.

[Miekko]

I don't know the specific case of Quechua, but I think case affixes usually originate from adpositions and ultimately from adverbs, nouns or verbs as the head of the construction. In any case, Quechua -qa attaches enclitically to the topic and is thus "on the same side" of the case suffixes.

Other things can turn into case affixes though - determiners and classifiers, for instance.