castling and en-passant are quite recent. They're not, really. They date back to middle ages. Quite recent is only that they were made "official" and rules wer

castling and en-passant are quite recent. They're not, really. They date back to middle ages. Quite recent is only that they were made "official" and rules were uniformized. As to memorization of openings, the current world champion Magnus Carlsen thinks the attention to opening theory is overrated. Yes, but you need to know the context in which he thinks it's "overrated" :) It's not unusual these days that more than half of the game is prepared at home. Eg. when Topalov played Anand in World Championship 2010, Anand lost the first game, because he forgot the correct 23rd move of his home preparation. The game went on for 7 more moves.