Natural selection can explain lactase persistence in humans. Human beings are born with the ability to digest lactase from their mother’s milk. As children stop breastfeeding and age, their ability to digest lactate diminishes. However, the domestication of animals led humans to begin to consume non-human dairy products and thus lactase at numbers greater than ever before.Therefore, lactase tolerance mutations arose more rapidly and prominently within populations that had domesticated cattle. Humans who are able to consume dairy and lactate had an evolutionary advantage over those who could not effectively digest lactase. As a result the environment selected for the mutation that allowed lactase tolerance to continue past breastfeeding years.
