In my current game I was researching Alphabet in the hopes of trading it to the two AIs I'd encountered. Alphabet never showed up on their Technolgies list while I was researching it. But once I discovered Alphabet, it did not show up on the Technolgies I could trade them. I continued on researching Writing and the same thing happened. I saw no indication that either had learned Writing (I did see they both learned Mysticism) and yet I could not trade it once it was discovered. This is the second game in which this has happened to me. In a previous one it happened on Alphabet, Writing, and Literature. Could it be that the AIs are learning this path at the same pace at which I am learning it? I thought so at first but having this repeat in a second game is too much coincidence. Is there some game mechanism in place which prevents me from trading these techs?