Alcohol dehydrogenase: "The enzyme is contained in the lining of the stomach and in the liver. It catalyzes the oxidation of ethanol to acetaldehyde:

CH3CH2OH + NAD+ → CH3CHO + NADH + H+
This allows the consumption of alcoholic beverages, but its evolutionary purpose is probably the breakdown of alcohols naturally contained in foods or produced by bacteria in the digestive tract. "

Also affects people of southeast asia.

I don't know anything about the rest of your post though