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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.
Studies have linked the occurrence of lactase persistence to two different single-nucleotide polymorphisms about 14 and 22 kilobases upstream of the 5'-end of the LPH gene. [26] Both mutations, C→T at position -13910 and G→ A at position -22018, have been independently linked to lactase persistence.
An example of the codominant inheritance of some of the four blood groups. Mendelian traits in humans are human traits that are substantially influenced by Mendelian inheritance . Most – if not all – Mendelian traits are also influenced by other genes, the environment, immune responses, and chance.
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 persistence One of the best known examples is the prevalence of the genotype for adult lactose absorption in human populations, such as Northern Europeans and some African societies, with a long history of raising cattle for milk.
Mendelian traits behave according to the model of monogenic or simple gene inheritance in which one gene corresponds to one trait. Discrete traits (as opposed to continuously varying traits such as height) with simple Mendelian inheritance patterns are relatively rare in nature, and many of the clearest examples in humans cause disorders.
The majority of humans actually follow this protocol as well, and down-regulate lactase production around 3-5 years of age. Interestingly, though, the majority of caucasians, mainly those from northern european background, continue to have elevated lactase activity all the way into adulthood, and so they exhibit “lactase persistence”.
Lactase persistence in humans evolved relatively recently (in the last 10,000 years) among some populations. Around 8,000 years ago in modern-day Turkey, humans became reliant on newly-domesticated animals that could be milked; such as cows, sheep, and goats. This resulted in higher frequency of lactase persistence. [79]