I have heard it said that the Middle Ages changed the genetic makeup of the European population to be more tolerant of alcohol, through a kind of Darwinistic weeding out of those who were most negatively affected by it, both physically and cognitively. There was so much alcohol during the middle ages, so the story goes, and it was so suddenly a major factor on cultural development, that alcohol tended to ruin lives and end the blood lines of those who were most (genetically) effected. The result is that the more alcohol tolerant blood lines were more likely to live on past the Middle Ages and therefore the gene pool as a whole is more

The Asian populations did not have a period like this and even less so the native Americans. So in those populations today there are still physical complications associated with alcohol that are much more prevalent than in the West, namely the symptoms that come with "Asian flush" such as headaches, dizziness, palpitations, and nausea occurring to a much greater degree in Asian drinkers than with Western drinkers. The incidence of "alcohol flush reaction" are not limited to Asia, but Asians are more genetically predisposed to it.

Is there any truth to the idea the Middle Ages played a role in all this?