I recently created a scenario in which I turned off science. The ai nevertheless was able to tech slowly.
I think the reason is that they can still use Great Scientists to get a free tech (Same may be true for the social policy of "free thought", but I disabled the tree by every civ giving the first piety policy).
Another bug: When science is turned off and, as a human player, you use a Great Scientist for getting a free tech, then the tech tree will be empty (you cannot chose a tech) and you cannot finish the turn. Same is true for the "free thought" policy.
I think the reason is that they can still use Great Scientists to get a free tech (Same may be true for the social policy of "free thought", but I disabled the tree by every civ giving the first piety policy).
Another bug: When science is turned off and, as a human player, you use a Great Scientist for getting a free tech, then the tech tree will be empty (you cannot chose a tech) and you cannot finish the turn. Same is true for the "free thought" policy.
