The following is a paper that I wrote for a bio-archaeology course in 2013 focusing on the interrelationship between human evolution and alcohol.
From a chemical perspective, alcohol is simply an organic molecule consisting of carbon attached to a hydroxyl functional group, with only saturated bonds. The form of alcohol that can be consumed by humans is ethanol. Ethanol consists of two carbons and the hydroxyl group and has an empirical formula of C2H5OH. The cultural definition of alcohol however varies greatly, as does the view on how alcohol affects one’s health. In some cultures, alcohol is considered a food source, while on others it is considered an “anti-food.” (Dietler M. 2006) In this paper, I will address the interrelationship between humans and ethanol from an evolutionary perspective, first noting why microorganisms produce alcohol, the impact on human evolution coming into contact with alcohol in nature had, and then addressing humanity’s overall mastering control over alcohol producing microbes in order to suit our wants and needs.
Humans use the help of yeasts in the production of alcohol. Yeasts are a group of unicellular fungi. The primary species of yeast used is Saccharomyces cerevisiae. Various strains of this yeast are used for the production of wines, beers, and also breads. (Stefanini I. 2012; McGovern P. E. 2009) Ethanol producing yeasts have existed for millions of years. An increase in fermentable sugars at the end of the Cretaceous, due to a surge in fruiting plants may have acted as a selective pressure in the evolution of ethanol producing yeasts. The production of ethanol by such yeasts, and their tolerance to relatively high concentrations of ethanol could be used to reduce competition. The ethanol produced could then be converted into usable energy for the yeast cells. S. cerevisiae especially combines factors such as “fast growth, efficient glucose repression, good ability to produce and consume ethanol, and a tolerance for several environmental stresses, such as high ethanol concentration and low oxygen levels.” These properties make S. cerevisiae particularly well suited to be harnessed for ethanol production by humans. (Piskur J et al. 2006)
Human ancestors have a long history with fermented fruits. As far back as 24 mya, dental morphology from hominid fossils show adaptations useful in consuming fruit (Dudley R. 2004; 5). These same adaptations are seen in modern hominids that tend to be frugivorous. Fruit that has fallen to the group and become overripe can contain as much as 5% alcohol. (McGovern, P. E. 2003.) Contact with ethanol early in our evolutionary history, would have been a selective pressure for the evolution of metabolic pathways, which could process ethanol. This may be why roughly “10% of the enzymes in the human liver, including alcohol dehydrogenase, function to generate energy from alcohol.” (McGovern, PE. 2009; 7361)
The human body handles ethanol through a metabolic pathway that involves converting the ethanol to acetaldehyde using a class of enzymes called aldehyde dehydrogenase, or ADH, and then further converting the acetaldehyde into acetate, which is then converted to CO2 by various muscles, as it spreads through the bloodstream. Side effects of alcohol consumption include hypoxia in organs that process the alcohol and tissue damage. (Zakhari S. 2006) Further complications from alcohol can occur due to the presence of congeners: impurities formed during the fermentation process. It is hypothesized that the presence of congeners are one of the primary causes of hangovers. (Howland J. et al. 2008) In one study “Hangover effects…were proportional to congener content, with brandy yielding the most severe effects and vodka yielding the least.” (Howland J. et al. 2008; 42)
There are a few prerequisites for large scale alcohol production. Pottery is necessary because it is used as a storage vessel for the fermenting beverages and also for long term storage of the product. The evidence of oldest use of pottery comes from China and indicates pottery has been produced for at least 20,000 years. (Wu X. et al. 2012) “Chemical analyses of ancient organics absorbed into pottery jars from the early Neolithic village of Jiahu in Henan province in China…revealed that a mixed fermented beverage of rice, honey, and fruit (hawthorn fruit and or grape) was being produced as early as the seventh millennium before Christ (B.C.).” (McGovern P.E. et al. 2004; 17593) This was found through a chemical analysis of Jiahu pottery shards. Because alcohol is volatile, there is little direct chemical evidence of alcohol within ancient holding vessels. “Fermentation of the mixed ingredients, however, can be inferred, because the ‘wine yeast’ (Saccharomyces cerevisiae) occurs in honey and on the skins of sugar-rich fruits.” (McGovern P.E. et al. 2004; 17597)
Two other innovations are necessary for the large scale production of alcohol in society: cultivation and domestication of source crops and the production of pottery. Because of their use as source material in the production of alcohol, no discussion of alcohol production would be complete without addressing the cultivation and domestication of various crops. This includes cereals such as wheat and rice, tubers such as potatoes, and fruits such as grapes. Cereals are a group of modified grass species that were first domesticated about 13,000 years ago. They include, among other crops, the triticeae: wheat, barley, and rye; rice and maize. (Glémin S. and Bataillon T. 2009) There is no single point of origin for the domestication of these crops. The process of domesticating various cereals occurred in multiple locations at multiple periods of time. (Remigereau M-S et al. 2011) Evidence suggests that rice was domesticated in China somewhere between 8,200 and 13,500 years ago (Molina, J. et al. 2011). Maize originated in the Americas. The exact origin is contested. It may have first been domesticated in Mexico roughly 9,000 years ago after which it spread across South America. (Matsuoka Y. 2002)
Wine is produced from varieties of the domesticated grape subspecies Vitis vinifera subsp. vinifera. Based on archaeological and genetic evidence, cultivation of domesticated grapes began roughly 6,000 – 8,000 years ago, in the near east. Approximately 8 million ha of vineyards are currently being maintained. Most of the grapes harvested are used in the production of wine. Changes due to domestication include larger berry size and a higher sugar content, as well as a wide variety of berry colors and the formation of perfect flowers: flowers which have both stamens and carpels (source: dictionary). Grape varieties can have flowers that are male, female, or perfect. Having perfect flowers improves fertility and thus yield. (“Breeding Grapes- Grape Flowers”; Myles S. 2011)
While hominids have been influenced by contact with ethanol in nature for millions of years, it may be that humans started influencing the direction of yeast evolution, through intentional fermentation, at least as far back as 11,000 years ago. While unicellular organisms like yeast might not generally come to mind when one hears the word domestication, humans have manipulated many microbial genomes both unintentionally and deliberately. In order to determine the time period in which domestication of yeast strains might have occurred, molecular analysis was done on various strains of S. cerevisiae and closely related wild species. Based on molecular analysis, two groups, the vineyard and sake groups split approximately 11,900 years ago, and the vineyard group and saké group saw further intragroup divergence approximately 2,700 and approximately 3,800 years ago, respectively. (Fay J. C. and Benavides J. A. 2005)
Based on available evidence, it is likely that S. cerevisiae was first used in the production of wine. DNA evidence dates winemaking to 3150 BC, and the earliest molecular evidence available indicates winemaking having taken place at least as early as 7000 BC in China. (Fay J. C. and Benavides J. A. 2005) There might be a reasonable explanation as to why the production of wine preceded the production of beer: S. cerevisiae is not an airborne yeast and therefore requires a vector, most likely social wasps. These wasps may also be responsible for providing a mechanism for overwintering. This was indicated when a study looking at the gut fauna of social wasps and bees identified various yeast strains including S. cerevisiae. The grapes would be inoculated with the yeast when a wasp bit into the fruit. (Stefanini I. 2012)
Even though beer was likely to be secondary advent because of the nature of how S. cerevisiae spreads, this is not to say that beer production always requires intentional inoculation with the yeast. Lambic beers are produced using naturally occurring yeasts and bacteria as such are produced in certain regions that have micro fauna populations capable of fermenting the wort, such as Belgium. (Lambic beer. 2013)
Can alcohol be considered a food source? The answer, it seems, is yes. “[S]ome varieties of alcoholic drinks have substantial nutritional value, and they may form a significant component of the diet of many peoples” (Dietler M. 2006; 231) M. Dietler addresses this point and suggests considering “…alcohol as a special class of food with psychoactive properties resulting from the application of alternative culinary techniques…” (Dietler M. (2006); 231) As evidence that one can survive on alcohol as a food source, J. Wilson, a “homebrewer and certified beer judge”, fasted on nothing but beer and water for 46 days. This was instigated by the legend of monks fasting on nothing but beer and water. Wilson noted that while he did have cravings, he began to realize that he did not need certain foods, but merely wanted them. However, he also noted that the type of beer he was consuming lacked enough protein to continue the fast longer than the 46 days. (“My Faith: What I learned from my 46-day beer-only fast”)
While alcohol does seem to have at least some nutritional content, this does not mean that it does not have its negative consequences. While it seems consumption of alcohol can be useful, over consumption can be destructive. This is evidenced by the case of ritual drunkenness as practices by the Quichua speakers in Otavalo, Ecuador. The Quichua speakers, descendants of the Inca commonly consume Chicha, a relatively low alcohol content drink produced from Maize, during religious ceremonies. However, with the introduction of high alcohol content drinks such as trago, a distilled liquor produced from sugarcane, alcoholism became a problem. Eventually the practice of ritual drunkenness in the region came to a stop due to the negative effects of overconsumption and because the people viewed a major earthquake as a sign from the gods to stop. (Butler B. 2006)
Alcoholic drinks were not only used as a food source. Herbalism, the treatment of disease using various herbs, has a long tradition. Many groups of people used herbal infused alcoholic drinks as forms of medicine. Once such usage was in Ancient Egypt. (McGovern P. E 2009) We still see remnants of this usage in modern productions of liquors such as Chartreuse: a liquor crafted from 130 different botanicals. According to the information provided by Chartreuse, the recipe was likely originally created by an alchemist. It was the Chartreuse monks who studied the recipe and recreated the product. The production is still managed by the monks. (History of the Chartreuse Liqueurs. 2013)
It should not be surprising to see clergy handling the development and production of alcohol. Many religious groups consider alcoholic drinks to be of religious importance. The Inca and their descendants, for instance, considered imbibing a low alcohol corn beer called chicha, even to the point of drunkenness, to be a form of paying respect to and communing with the gods. This treatment of alcohol can act as a social glue. It brings people together and encourages them to interact with one another. In the same way, bars can act as a social glue in secular cultures. (Butler B. 2006) This gives us an alternative view into alcohol use as being a benefit, at least to some extent, for society, rather than just a pathology.
Humans and alcohol have a long history. Alcohol had both direct and indirect impacts on our evolution. The presence of fermenting sugars in fruits created a selective pressure for humans to evolve metabolic pathways to break down alcohol into non toxic compounds such as Carbon Dioxide. Once humans mastered agriculture, domestication, and tool use, we began taking control of alcohol production. We then began using it not only for recreational use, but for medical use and in the production of foods such as bread. Thus fermentation of sugars using S. cerevisiae, the primary method of alcohol production became of great economic importance to humans. However, at the same time, overconsumption of alcohol, and more so the ability to produce beverages with high concentration of alcohol has created conditions of alcoholism in within populations such as the Quichua speakers of Ecuador. Overall, I found that the prevalence of alcohol production has had both positive and negative impacts on societal and individual levels.
Butler B. 2006. Holy Intoxication to Drunken Dissipation: Alcohol Among Quichua Speakers in Otavalo, Ecuador. New Mexico: University of New Mexico Press
Dietler M. 2006. Alcohol: Anthropological/Archaeological Perspectives. Annual Review of Anthropology. 35:229-249
Dudley R. 2004. Ethanol, Fruit Ripening, and the Historical Origins of Human Alcoholism in Primate Frugivory. Integrative and Comparative Biology. 44, No. 4:315-323
Fay J. C. and Benavides JA. 2005. Evidence for domesticated and wild populations of Saccharomyces cerevisiae. PLoS Genet 1(1): e5
Glémin S. and Bataillon T. 2009. A Comparative View of the Evolution of Grasses under Domestication. New Phytologist, Vol. 183, No. 2: pp. 273-290
Heun M, Schäfer-Pregl R, Klawan D, Castagna R, Accerbi M, Borghi B. and Salamini F. 1997. Science , New Series, Vol. 278, No. 5341:1312-1314
Howland J. Rohsenow D. J. and Edwards E. M. 2008. Are Some Drinkers Resistant to Hangover? A Literature Review. Current Drug Abuse Reviews, vol 1:42-46
Matsuoka Y, Vigouroux Y, Goodman M. M. Sanchez G. J, Buckler E, and Doebley J. 2002. A single domestication for maize shown by multilocus microsatellite genotyping. Proc. Natl. Acad. Sci. USA, Vol. 99 No 9: 6080-6084
McGovern, P. E. 2003. Ancient Wine: The Search for the Origins of Viniculture. Princeton: Princeton University Press. p. 314
McGovern P. E, Mirzoian A, Hall GR. and Bar-Yosef O. 2009. Ancient Egyptian Herbal Wines. Proceedings of the National Academy of Sciences of the United States of America. 106, No. 18:7361-7366
McGovern P. E, Zhang J., Tang J., Zhang Z., Hall GR., Moreau RA., Nuñez A., Butrym ED., Richards MP., Wang C., Cheng G., Zhao Z., Wang C. and Bar-Yosef O. 2004. Fermented Beverages of Pre- and Proto-Historic China. Proceedings of the National Academy of Sciences of the United States of America. 101, No. 51:17593-17598
Molina, J, Sikora, M, Garud, N, Flowers, J. M, Rubinstein, S, Reynolds, A, Huang, P, Jackson, S, Schaal, B. A, Bustamante, C. D, Boyko, A. R. and Purugganan, M. D. (2011). “Molecular evidence for a single evolutionary origin of domesticated rice”. Proceedings of the National Academy of Sciences 108 (20): 8351.
Myles S, Boyko A. R, Owens C. L, Brown P. J, Grassi F, Aradhya M. K, Prins B, Reynolds A, Chia J-M, Ware D, Bustamante C. D, and Buckler E. S. 2011. Genetic structure and domestication history of the grape PNAS. published ahead of print January 18, doi:10.1073/pnas.1009363108
Omenn GS. and Ellison PT. 2010. Evolution and Public Health. Proceedings of the National Academy of Sciences of the United States of America. 107, Supplement 1: Evolution in Health and Medicine: 1702-1709
Piskur J, Rozpedowska E, Polakova S, Merico A, Compagno C. 2006. How did Saccharomyces evolve to become a good brewer? Trends Genet vol 22(4):183-6.
Remigereau M-S, Lakis G, Rekima S, Leveugle M, Fontaine MC, et al. (2011) Cereal Domestication and Evolution of Branching: Evidence for Soft Selection in the Tb1 Orthologue of Pearl Millet (Pennisetum glaucum [L.] R. Br.). PLoS ONE 6(7): e22404. doi:10.1371/journal.pone.0022404
Smith F. H. 2008. The Archaeology of Alcohol and Drinking: American Antiquity: University Press of Florida.
Stefanini I, Dapporto L, Legras J-L, Calabretta A, Paola M. Di, Filippo C. De, Viola R, Capretti P, Polsinell M, Turillazzi S., and Cavalieri D. 2012. Role of social wasps in Saccharomyces cerevisiae ecology and evolution PNAS. published ahead of print July 30, 2012, doi:10.1073/pnas.1208362109
Wu X, Zhang C, Goldberg P, Cohen D, Pan Y, Arpin T and Bar-Yosef O. Early Pottery at 20,000 Years Ago in Xianrendong Cave, China. 2012. Science, New Series, Vol. 336, No. 6089: 1696-1700
Zakhari S. 2006. Overview: how is alcohol metabolized by the body? Alcohol Res Health.. 29(4). 245-54.
Breeding Grapes – Grape Flowers (2013). Accessed from http://www.hort.cornell.edu/reisch/grapegenetics/breeding/crossing1.html
cereal. (2013). In Encyclopædia Britannica. Retrieved from http://www.britannica.com/EBchecked/topic/103301/cereal
History of the Chartreuse Liqueurs. (2013) in Chartreuse. Retrieved from http://www.chartreuse.fr/history-of-the-liqueurs;article;40;uk.html
lambic beer. (2013). In Encyclopædia Britannica. Retrieved from http://www.britannica.com/EBchecked/topic/1064631/lambic-beer
“My Faith: What I learned from my 46-day beer-only fast” (2013). in CNN Belief Blog – CNN.com Blogs. Accessed from http://religion.blogs.cnn.com/2012/02/25/my-take-what-i-learned-from-my-46-day-beer-only-fast/
- Some works mentioned in the bibliography were not expressly mentioned in the paper. However, since I had read these works in order to formulate an opinion, I decided that it was appropriate to include them regardless.