Rice, alcohol and genes

Changes in human diet driven by cultural evolution seem to be at the root of many relatively recently emerged patterns of genetic variation. In particular, lactase persistence and varied production of amylase are two well known cases. Both of these new evolutionary genetic developments are responses to the shift toward carbohydrates over the last 10,000 years as mainstays of caloric intake. Rice and wheat serve as the foundations of much of human civilization. It is notable that both China and India are divided into rice and wheat (or millet) belts, so essential are modes of agriculture in our categorizations of societies. Even nomad societies are dependent on carbohydrates in the form of "simple sugars," as much of the nutritive value of milk is from its lactose sugar. Carbohydrates are convenient because they can be grown and controlled by humans, but also because they can be stored, and finally, reprocessed. Some of that reprocessing is straightforward, such as with breads, but for this post alcohol is what we are concerned with. Tom Standage's A History of the World in 6 Glasses documents the importance of beer & wine in ancient human societies (and hard liquor in modern ones), and also argues from both empirics and theory that fermented beverages are almost an inevitability in an agricultural society. Alcohol is rich in energy, portable, keeps, and, has a far lower pathogenic load than water in a pre-modern environment. Not to mention the pleasant "buzz" it provides. But like milk, those "without tolerance" often suffer negative physiological consequences. It turns out that like LCT, the locus critical in controlling the levels of the enzyme lactase, the alcohol metabolization loci exhibit variation across populations. A new paper is out which argues for the causal connection between the spread of rice agriculture, and a derived variant of ADH1B, The ADH1B Arg47His polymorphism in East Asian populations and expansion of rice domestication in history: