Hi Jaybird —
There's a lot of websites that insist on this point, but really it's not 'case closed' and nowhere near as certain as we'd like to think.
Certainly Origen's theology was often genius, and often skated close to the edge. The Church Fathers believed that the Word of Scripture was true, and that their faith was reasonable, and therefore could be reasoned philosophically. They were nearly all Platonists by training, and at times their Christianity seemed remarkably Platonic, their Platonism remarkably Christian. It's a fine line. Platonic Christianity will inevitably lead to questionable beliefs — Arius for example — whereas Christian Platonism has produced some of the most lucid theological voices in the Tradition: Augustine and Aquinas, for example.
There was a time when I might challenge and denounce the above point by point, but those days have passed. All I will say now is be careful what you read on the web, look to what is being said, who is saying it, what sources is the argument based on, and then try and double-check those sources. The misrepresentation and fabrication surrounding Origen by the pro-reincarnationalists is a textbook example of 'fake news'.
As ever, as long as people think that reincarnation means "I" get another bite of the cherry, we're really into a misunderstanding of the original doctrine in its own context, let alone how it might appear in other traditions.
To understand Origen's ideas about the migration of souls, you'll need to look into the Greek ideas about metempsychosis.
The history of the doctrine is uncertain, and some would claim therefore that it was imported from Asia. Personally I like to think it arose naturally, from the observation of nature. Man of Antiquity thought cyclically, so it's hardly surprising his speculations would be along those lines.
Orphism and the Eleusian mysteries appear around 6BC, then through Pythagoras, Plato and on...
One thing I might throw in — the belief that man might reincarnate as an animal, insect or other is worse than condemnation to a period in hell. Logically, as far as kara is concerned, once you step below the human threshold, you are ••••••. There's no way back, as animals are fixed in their nature. It's just one of the many populist teachings on reincarnation that I find chilling.
