European Cognitive Abilities, Medieval and Modern

Cognitive Evolution in Western Europe, by Peter Frost at Aporia 

As average cognitive ability increased, so did the numbers of the highly intelligent. They were becoming a class of their own... Progress is driven not only by individuals but also by communities that can fully appreciate new ideas and put them to good use. Otherwise, new ideas are left to rot on the vine. For example, the printing press wasn’t really invented by Johannes Gutenberg in 1440 — this was when it became commercially viable. 

He places the inflection point around 1350, which naturally suggests a change in culture and thus selection at the time of the Black Death. If you think you would have just killed it as a thinker before then, likely not. Unless you found one of the few niches you could exploit, your knowledge of the solar system, germ theory, and the Second Law of Thermodynamics would not help you much. The larger monasteries in strong networks would be about the only place you would find people who could follow your reasoning after a few minutes, and those would um, at least reduce your chances of passing on your superior genetics. Hanging out with Jews for knowledge of medicine and accounting might have helped, but you would have acquired extra physical risks for that.

Tangent: He quotes a now-standard estimate of 30-60% of Europe's population dying from plague at that timed.  When I was in school "as much as one-third" was the usual phrasing, which crept up gradually to 40 and 50%. The numbers stopped rising about fifteen years ago, when I would read occasional 60 or 70% estimates. I had a brief conversation then with an historical researcher while we were on vacation who lowered his voice and said in not only towns but small regions the numbers reached 80% death, according to cemetery studies. At that point the towns simply folded, no further bodies were buried there, and the survivors moved to functioning communities, disguising the population decreases there. That is getting into the range of New World death from European (and in western South America, Oriental*) diseases.

Extra controversies are dropped in along the way because well, Peter Frost . 

*Pacific silver trade, similar diseases to Atlantic seaboard