Question

Think about an environment where early humans did not domesticate cows and an environment where early humans domesticated cows. If you measured how common the mutant LCT allele was in each environment, what would you expect to find and why?

Answer 1

LCT gene stands for lactase gene. The lactase enzyme helps digest milk. Generally, the ability to digest lactose is more in childhood and it slowly disappears in the adulthood in mammals, including humans, i.e., they become lactose - intolerant. Now mutation of LCT allele will lead to maintanance of the ability to digest lactose even in the adulthood.

Humans, thousands of years ago, started to domesticate cows. They started milking for their consumption purpose. This is when mutations near the LCT gene became more frequent and humans became lactose - tolerant. Thus, domestication of cows lead to frequent mutations in the LCT allele. The ability to be lactose tolerant and digest lactose even in adulthood was favored and is a biggest example of natural selection in genome. This kind of evolution is an example of convergent evolution.

Thus, in an environment where humans did not domesticate cows, the frequency of LCT allele mutation was low, and, in the environment where humans domesticated cows, the mutation in the LCT allele is more frequent.