Do we know for sure what was in the Beaker People's beakers?
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Alcohol is reckoned to have been invented in the Middle East, no doubt. If so, wouldn't it have spread equally sideways?
Alcohol is poisonous and resistance to its effects is genetic. World-leading piss artists in the extreme west of the Old World; light-weights-floored-by-half-a-pint in the extreme east. Guess who's been routinely alcohol-soaked longest?