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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.
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.
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]
Lactase is an enzyme that some people are unable to produce in their small intestine. [2] Technology to produce lactose-free milk, ice cream, and yogurt was developed by the USDA Agricultural Research Service in 1985. [3]
In humans, in non-dairy consuming societies, lactase production usually drops about 90% during the first four years of life, although the exact drop over time varies widely. [190] Lactase activity persistence in adults is associated with two polymorphisms: C/T 13910 and G/A 22018 located in the MCM6 gene. [191]
The MCM complex consisting of MCM6 (this protein) and MCM2, 4 and 7 possesses DNA helicase activity, and may act as a DNA unwinding enzyme.The hexameric protein complex formed by the MCM proteins is a key component of the pre-replication complex (pre-RC) and may be involved in the formation of replication forks and in the recruitment of other DNA replication related proteins.
English: Interpolated map of the percentage of adults with a known lactase persistence genotype (-14010 G>C, -13915 T>G, -13907 C>G or -13910 C>T) in the indigenous population of the Old World. Circles mark the sample locations.