In some human populations, though, lactase persistence has recently evolved as an adaptation to the consumption of nonhuman milk and dairy products beyond infancy. The majority of people around the world remain lactase nonpersistent, and consequently are affected by varying degrees of lactose intolerance as adults.
Why is lactase persistence an adaptation in some groups?
Lactase persistence—the ability of adults to digest the lactose in milk—varies widely in frequency across human populations. This trait represents an adaptation to the domestication of dairying animals and the subsequent consumption of their milk.
Do all human individuals who are lactose persistence have the same genetic mutation?
Some humans, however, continue to produce lactase throughout adulthood, a trait known as lactase persistence. In European populations, a single mutation (−13910*T) explains the distribution of the phenotype, whereas several mutations are associated with it in Africa and the Middle East.
Why lactase persistence mutations are found in some populations and not others?
The lactase-persistence mutation would become common if it provided a survival and reproductive advantage in a particular environment. For example, in a population with domesticated cows, where milk is available, the ability to drink milk might have been advantageous in periods of drought or when food was limited.
Why is lactose persistence evolved in humans?
But around 8,000 years ago in what's now Turkey — just when humans were starting to milk newly domesticated cows, goats and sheep — mutations near the gene that produces the lactase enzyme started becoming more frequent. And around the same time, adult lactose tolerance developed.
Why did lactase persistence only evolve in some human populations?
Since lactase's only function is the digestion of lactose in milk, in most mammal species, the activity of the enzyme is dramatically reduced after weaning. In some human populations, though, lactase persistence has recently evolved as an adaptation to the consumption of nonhuman milk and dairy products beyond infancy.
Is lactase persistence dominant or recessive?
Lactase persistence is an autosomal-dominant trait that is common in European-derived populations.
Why is lactase persistence more prevalent in indigenous populations?
The competitive advantage conferred on lactose-tolerant individuals would have given rise to strong selective pressures for this genotype, especially in times of starvation and famine, which in turn gave rise to higher frequencies in lactase persistence within the populations.
Is lactase persistence genetic?
In other healthy humans, lactase activity persists at a high level throughout adult life, enabling them to digest lactose as adults. This dominantly inherited genetic trait is known as lactase persistence.
In what regions of the world is lactase persistence most prevalent?
Lactase persistence is common in people of European ancestry as well as some African, Middle Eastern and Southern Asian groups, but is rare or absent elsewhere in the world.