Natural Selection for Lactose Tolerance

This animation shows how a mutation that allows adult humans to digest milk can be lost or spread under different circumstances.

Whether a mutation provides an advantage in the course of human evolution depends on both environmental and cultural factors. Advantageous mutations can spread rapidly through a population due to natural selection. The animation illustrates an example of this process with a mutation that allows adult humans to produce lactase, an enzyme used to digest milk, in cultures that have adopted dairy farming.

Depending on students’ background, it may be helpful to pause the animation at various points to discuss different components or steps of natural selection.