Lactase Persistance in Adults

Human populations adapt and develop according to their environmental and cultural surroundings. As stated in Dr. Richard McElreath's online lecture, Introduction to Human Evolution, cultural variation is more prominent than genetic variation between different human populations. Survival methods and diet are distinct cultural customs of every population, thus traditions and habits such as food processing skills are passed on from one generation to the next. This was the result of the transfer of information and genes over time which constituted the ability to break down and digest lactose past youthful stages of development, allowing human adults to drink milk.

Most individuals cease to produce lactase after weaning, typically around the age of five, only some human populations develop and pass on the genetic mutation which allows for the tolerance of lactose otherwise known as lactase persistence. Lactase persistence enables an individual to carry the lactase enzyme which breaks lactose down into more digestible forms of glucose and galactose (Check. E pg. 994). According to Erika Check in her article “How Africa Learned to Love the Cow” most groups which develop this tolerance to lactose happen to be pastoralist or semi-pastoralist groups who rely on herding for survival. Many pastoral cultures reside in sub-Saharan Africa, these include the Zulu, Xhosa, and Swazi people who devote themselves to their Nguni cattle. In addition, most northern Europeans and a number of North African and Arabian populations also retain the ability to digest lactose as adults (Boyd R. & Silk J. pg. 347). The ability to digest lactose as an adult is controlled by a single dominant gene. The discovery of the genetic basis for lactose intolerance ...

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...e, but perhaps lose the attribution when reproducing causing future generations to cease to be tolerant to drinking milk as adults.

Natural selection generally favors attributes that ultimately increase the relative fitness of individuals. Cultures whose ancestors herded cattle evolved to make use of their milk; in maximizing the use of their resources they increased their fitness and chances of survival. To several other populations, drinking milk may not be so advantageous and therefore the lack of the dominant allele has very little affect on their well being with consideration to their ecological environment.

Works Cited

Boyd, R. and Silk, J. B. 1997. How humans evolved. 6th ed. New York: W.W. Norton & Company.

Check, Erika. 2006. How Africa Learned to Love the Cow. Nature Vol 444: 994-996.

Dr. Richard McElreath. 2014. 3.01 Introduction to Human Evolution.