AI never researches Xeno Ethics?

From what I have seen the AIs are slow to research Xeno Ethics but evenually, they will. However, the AIs are very slow to research the techs after Xeno Ethics which give them access to the special good/evil/neutral planet buildings. If I'm not mistaken, the neutral AIs are usually 1st to research Xeno Ethics since it gives them access to all of the planet tiles.

How many years does it take them? They just seem to climb the weapn tech trees.

I usually research it and trade it and get lots of goodies for it!

I try never to trade Xeno Ethics, at least early to mid game, because of the incredible bonuses it brings. But the AI will EVENTUALLY research Xeno Ethics, if only because it finishes researching everything else. But I believe it assigns Xeno Ethics a lower priority, possibly because all the computer AI's are basicaly *set* in their alignments and aren't programmed to recognize the benefits it would provide them (aside from influence and diplomacy bonuses), assuming a random event doesn't turn them evil.

They research it between 2230 and 2235

I usallu have to buy xeno ethics off the AI for 200-300 BC

Generally after a few years all but two AIs are left and then soon after it's one left and it's me and them if I haven't conquered them by then.