Well, this is an interesting subject, tabú since racial critic differences are involved.
In the matter are involved the enzimes, as lactasa and Deshidrogenasa (spanish).
European population have been exposed to non processed (non fermented mainly) milk in adult stages as well to exposed to alcohol in critic episodes of the vital life (read here previous copulation or previous battle).
Alcohol exposure has been a constant in europeans.
We will understand easily that the less adapted (read here: the individual with less amount of the specific enzyme to "deal" with the alcohol, for example) had less success in the sexual relation after drinking lots of alcohol in the solstice party in a celtiberian tribe (as european example) or would have his motricity enough afected in a violent confrontation that would impede of difficult the survival. (selective breed).
The same happens with the adults with tolerance to the lactose (presence in adult stages of lactase enzyme, only produced in early stages except mutations). They would have extra amount of decisive nutrients.
So, the alcoholism seems to be more common in europeans than in asiatic, for example, because the major presence of deshidrogenasa among the first, would act as a "shield" that will hide the nocive effects of alcohol until reaching critical stages of dependence.
It's quite easy see this example among southamericans, whose tolerance or "mal beber" ("bad drinking" -losing easily control and massive behaviour consequences with low amount of alcohol, related to low presence of deshidrogenasa-) can be easily related to the amerindian phenotype.
