Narrator: This is Science Today. When we think about what distinguishes humans from non-human primates, we often refer to the fossil record. But Katie Pollard, an associate professor at the University of California, San Francisco's Institute of Human Genetics, says our DNA offers vital information, too — including about the human diet.
Pollard: No other mammal drinks milk into adulthood. That's a uniquely human trait and it's enabled by changes in the lactase gene, which allow us to have the correct enzyme for breaking down the sugars in milk into adulthood.
Narrator: Pollard explains that most non-human primates eat mostly fruits and do not have anywhere near the omnivorous diet that humans have. As for the ability to drink milk into adulthood, the main reason was to access rich sources of calories.
Pollard: Our ancestors really lived in a leaner world. And any way that you could learn as a species to exploit a new food resource, especially one that other creatures like you weren't using, would be a huge advantage.
Narrator: For Science Today, I'm Larissa Branin.