Any city that builds an early wonder should try to get a library up ASAP and run 2 scientists non-stop (or more if in Caste) to lower the chances of getting a non-GS. Our first great person should be a pure-bred GS from Science but after that, all bets are off. These early wonders really could mess with our gene pool. Maybe we shouldn't complete the Great Wall unless we absolutely need to cash in on the fail gold. We'll already have the Oracle and the 'Mids dirty gene pools to deal with so why add to our mess if we don't have to?