A cattle herder drives his animals in Tanzania. The study linked the spread of pastoralism with the ability to digest milk. Credit: University of Pennsylvania
Babies are born with the ability to digest lactose, the sugar found in milk, but most humans lose this ability after infancy because of declining levels of the lactose-digesting enzyme lactase. People who maintain high levels of lactase reap the nutritive benefits of milk, however, offering a potential evolutionary advantage to lactase persistence, or what is commonly known as lactose tolerance.
A new study led by University of Pennsylvania researchers -- constituting the largest examination ever of lactase persistence in geographically diverse populations of Africans -- investigated the genetic origins of this trait and offers support to the idea that the ability to digest milk was a powerful selective force in a variety of African populations which raised cattle and consumed the animals' fresh milk.
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