Why would lactase persistence be common in some human populations but rare or absent in other human populations?

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.

What is the genetic reason for lactase persistence?

a Lactase genes

What is one way we can explain how lactose intolerance evolved in the human population?

Thousands of years ago, a mutation in the human genome allowed many adults to digest lactose and drink milk. Up until several thousand years ago, that enzyme turned off once a person grew into adulthood — meaning most adults were lactose intolerant (or “lactase nonpersistent,” as scientists call it).

Why do humans drink cow milk instead of human milk?

Cow milk is abundant so humans have become used to drinking it more than human milk, then it has become a preference even if human milk would become abundant. The reason that cow milk is considered as substitute to human milk is because of the fat percentage present in cow milk is similar to that of human milk.

When did humans become lactose tolerant?

The pattern was the same for all mammals: At the end of infancy, we became lactose-intolerant for life. Two hundred thousand years later, around 10,000 B.C., this began to change. A genetic mutation appeared, somewhere near modern-day Turkey, that jammed the lactase-production gene permanently in the “on” position.

What is the relationship between being lactase persistent and lactose tolerant?

Genetics of Lactase Persistence Lactase persistence, and therefore lactose tolerance, is inherited as a dominant trait. Lactose intolerance is the result of being homozygous for the recessive lactase allele that is poorly expressed after early childhood.

Why is lactase persistence an example of convergent evolution?

Once the lactase persistence trait evolved, it quickly spread across northern Europe. A separate independent mutation to the same regulatory DNA region conferred lactase persistence to at least one culture of humans living in Africa (e.g., convergent evolution).

Why do humans become lactose intolerant?

Too little of an enzyme produced in your small intestine (lactase) is usually responsible for lactose intolerance. You can have low levels of lactase and still be able to digest milk products. But if your levels are too low you become lactose intolerant, leading to symptoms after you eat or drink dairy.

Do humans become lactose intolerant?

Approximately 65 percent of the human population has a reduced ability to digest lactose after infancy. Lactose intolerance in adulthood is most prevalent in people of East Asian descent, with 70 to 100 percent of people affected in these communities.

Why humans are lactose intolerant?

Lactose intolerance happens when your small intestine does not make enough of a digestive enzyme called lactase. Lactase breaks down the lactose in food so your body can absorb it. People who are lactose intolerant have unpleasant symptoms after eating or drinking milk or milk products.

Why do some people develop lactose intolerance later in life?

Some individuals have inherited changes in this element that lead to sustained lactase production in the small intestine and the ability to digest lactose throughout life. People without these changes have a reduced ability to digest lactose as they get older, resulting in the signs and symptoms of lactose intolerance.

Did humans evolve to digest lactose?

The ability to digest lactose is also evidence that humans are still evolving. In those 10,000 years, it arose independently in at least four places around the globe. Today, more than 90 percent of all people have some degree of lactose tolerance.

What is the role of lactose Quizlet?

Q1. What is the role of lactose? Lactose is the principal sugar (or carbohydrate) naturally found in milk and dairy. Lactose is composed of glucose and galactose, two simpler sugars used as energy directly by our body. Lactase, an enzyme, splits lactose into glucose and galactose.

Is intestinal lactase expression induced by lactose feeding?

Human studies that have attempted to induce intestinal lactase expression with different lactose feeding protocols have consistently shown lack of enzyme induction. Similarly, withdrawing lactose from the diet does not reduce intestinal lactase expression.