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==Evolution and Agriculture==
Natural selection, the process first uncovered by Charles Darwin, tells us that specific traits, over time, could become selected for, leading to a transformed species as given traits become advantageous for reproduction.<ref>For information on the process of natural selection, see: Endler, John A. 1986. ''Natural Selection in the Wild''. Monographs in Population Biology 21. Princeton, N.J: Princeton University Press.</ref> Dairy consumption, in fact, is an example of how relatively recent natural selection pressures have transformed our human DNA. Over 11,000 years ago, that is before the invention of agriculture, almost all societies depended on hunting and gathering. Their diets were much more diverse than ours and consumed a large variety of meats, fruits, and vegetables.<ref> For information on the human diet in pre-agricultural societies, see: Hockett, Bryan, and Jonathan Haws. 2003. “Nutritional Ecology and Diachronic Trends in Paleolithic Diet and Health.” ''Evolutionary Anthropology: Issues, News, and Reviews'' 12 (5): 211–16. dos:10.1002/evan.10116. </ref> However, dairy was not a caloric resource they would have typically encountered during adulthood.
During the rise of agriculture in the Near East at about 11,000 years ago, we see that sheep, goats, and cows were among the earliest animals domesticated. Other early domesticates include dogs and pigs. As all mammals produce milk, this led to early agricultural villages having now far greater dairy resources naturally available. Initially, very likely dairy would not have been easily consumed by adults and perhaps even avoided; however, genetic mutations naturally show a very small percentage of the human population would have had alleles or groups of genes that allow for the consumption of dairy later in life (i.e., they are lactose persistent).<ref> For genetic information about lactose persistence in pre-agriculture humans, see: Knapp, Michael, Carles Lalueza-Fox, and Michael Hofreiter. 2015. “Re-Inventing Ancient Human DNA.” ''Investigative Genetics 6'' (1). dos:10.1186/s13323-015-0020-4.</ref>
This is made possible by the production of the lactase enzyme need to breakdown lactose into digestible carbohydrates. With greater availability of milk in early settled societies, the advantages of having a high caloric product that has calcium and fats that are beneficial became a greater selective pressure for human populations. The genes that then produce the lactase enzyme became selected for or gave advantages to given human populations that then allowed the consumption of lactose found in diary. The fact that milk was utilized very early in the Near East has meant that populations there do show a relatively high ratio of lactose persistence in adulthood (Figure 1).