As different individuals and races are very different comparing this trait, alcohol tolerance has/is probably under heavy genetic selection. As there isn't much alcohol outside human society, i wonder whether people craved alcohol by accident already before it became abundant or did that trait also become more prominent after alcoholic inventions. If the first one is true then possibly people less affected by alcohol gave more children but the whole group became vulnerable compared to sober human populations. If the latter is true then it was beneficial being able to consume alcohol and doing a lot of it. As i understand light alcohol (5%) does in fact hydrate you? and is less prone to becoming poisonous in other ways? Also why alcohol tolerance became strongest in Europe, Mediterranean? More suitable climate and more extensive trade relationships?