Evo-Ed: Integrative Cases in Evolution Education

Humans are relatively unique among mammal species in that some of their adult population retains the ability to digest lactose, a sugar found in milk. This ability is the result of a mutation that occurred thousands of years ago, and that must have conferred some adaptive advantage to those with the trait. This module will explore how, where, and why this evolutionary event took place.

Molecular Genetics

How can some humans continue to consume milk after they are weaned from breast-feeding? A single nucleotide mutation with a regulatory region of the LCT gene can determine if an adult is lactase persistent or lactose intolerant.

Cell Biology

The presence or absence of the lactase enzyme in the intestine determines whether dairy products are a good source of calories or a potential cause of dysentery. Converting lactose into galactose and glucose can provide useful cellular energy.

Anthropology and Biogeography

The ability to consume milk as an adult probably provided Neolithic farmers with an alternate and reliable calorie source. 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).