Yi Peng et al. The ADH1B Arg47His polymorphism in East Asian populations and expansion of rice domestication in history. BMC Evolutionary Biology, 2010. Open access.
The authors have mapped the allele for alcohol intolerance within the gene among Chinese populations, both Han and non-Han (cf. table 1 for frequencies). There are sharp differences among ethnicities with Tibeto-Burman and Austroasiatic nations showing low levels of the allele.
The highest densities of the allele are in the province of Zhejiang, just south of Shanghai, where nearly everybody is alcohol intolerant. The authors have estimated possible ages for the origin and spread of this allele and conclude that it originated and spread with rice agriculture. However I am not fully convinced, as happens with all molecular clock estimates. Whatever the case it does seem reasonable to accept that the seemingly oldest variants of the allele are in Central/South Western China.
Above: map of the alcohol intolerance allele included in the study (notice that the Chinese border is pretty much fictitious, including all claims the PRC may have) with clines of frequency and symbols for different estimated ages.
Notice that if the claim of Neolithic origin and spread of this allele is correct it would frontally clash with the notion that the Mongoloid morphotype spread within this same period. Personally I am pretty much skeptic of both claims. However I can imagine that this allele may have spread along some South to North demic expansion like the one associated to Y-DNA haplogroup O maybe.