If you thought it interesting that women have less of aldehyde dehydrogenase, then you'll no doubt be interested to know that many Asians have a deficiency.(1) This is why Chinese, Japanese and Koreans can be much more sensitive to alcohol than Europeans and Americans of European ancestry.(1) You'll notice that Asians with this deficiency are susceptible to alcohol-induced flushing.(1)
The adaptation that those of European ancestry have to be able to handle alcohol may be due differences of water intake in the continents, according to Sharon Moalem, Ph.D.(2) To reduce disease by avoiding pathogens in the water, early Asians boiled water for drinking tea.(2) Early Europeans, however, may have used fermentation so the alcohol would kill the pathogens.(2)
1. Wall, TL, Peterson, CM, Peterson, KP, Johnson, ML, Thomasson, HR, et al. Alcohol Metabolism in Asian-American Men with Genetic Polymorphisms of Aldehyde Dehydrogenase. Annals of Internal Medicine; September 2007:127(5)376-379. Available at http://www.annals.org/cgi/content/full/127/5/376. Accessed on October 4, 2008.
2. Moalem, S. Survival of the Sickest: The Surprising Connections Between Disease and Longevity; 2006. New York: HarperCollins.