2008) suggest that if selective factors are responsible for the high ALDH2*2 frequency in East Asia, their nature may be unrelated to the current association with esophageal cancer or ethanol metabolism. Alternative hypotheses of increased resistance to some disease organisms (Enoch and Goldman, 1990;Yokoyama et al., 2001; Oota et al., 2004; Yokoyama & Omori, 2005; Yang et al., 2007; Li et al., 2008) would also explain a clear advantage to heterozygotes. However, statistically positive selection on ALDH2*504Lys cannot be detected using the extended haplotype test (Sabeti et al., 2007) as very low levels of recombination exist in the genomic region of ALDH2 locus (Oota et al., 2004). Other methods suggest positive selection on ALDH2*504Lys (Long et al., 2006).
