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Therefore, lactase persistence is often cited as an example of both recent human evolution [15] and, as lactase persistence is a genetic trait but animal husbandry a cultural trait, gene-culture coevolution in the mutual human-animal symbiosis initiated with the advent of agriculture.
An example of this is the demographic transition, which describes the fall of birth rates within industrialized societies. Dual inheritance theorists hypothesize that the demographic transition may be a result of a prestige bias, where individuals that forgo reproduction to gain more influence in industrial societies are more likely to be ...
A well-researched example is the finding that dairy farming created the selection pressure that led to the spread of alleles for adult lactase persistence. [30] Analyses of the human genome have identified many hundreds of genes subject to recent selection, and human cultural activities are thought to be a major source of selection in many cases.
Lactase persistence is a rare ability among mammals. [74] Because it involves a single gene, it is a simple example of convergent evolution in humans. Other examples of convergent evolution, such as the light skin of Europeans and East Asians or the various means of resistance to malaria, are much more complicated.
Lactase (EC 3.2.1.108) is an enzyme produced by many organisms and is essential to the complete digestion of whole milk.It breaks down the sugar lactose into its component parts, galactose and glucose.
In most mammals, production of lactase diminishes after infants are weaned from maternal milk. However, 5% to 90% of the human population possess an advantageous autosomal mutation in which lactase production persists after infancy. The geographic distribution of lactase persistence is concordant with areas of high milk intake.
Analysis of his nuclear DNA indicates that he was a typical member of the Western European hunter-gatherer population at the time, with a most likely phenotype of blue-green eyes, dark brown or black hair, and dark or dark-to-black skin, with no genetic adaption for lactase persistence into adulthood. [4]
Lactase persistence [ edit ] In one study, five ancient DNA samples from Yamnaya sites had a frequency of over 25% of an allele that is associated with lactase persistence , conferring lactose tolerance into adulthood . [ 45 ]