Neanderthals and ancient humans adapted to eating starch-rich diets 100,000 years ago, far earlier than previously believed, according to a new study on the evolutionary history of the human oral microbiome.
According to the findings, such foods became important in the human diet long before farming and even before modern humans evolved.
And, although these early humans were probably unaware of it, the advantages of introducing the foods into their diet undoubtedly aided in the expansion of the human brain due to the glucose in starch, which is the brain's main fuel source.
"We think we're seeing evidence of a really ancient behavior that might have been part encephalization, or the growth of the human brain," said Harvard Professor Christina Warinner, Ph.D. '10. "It's evidence of a new food source that early humans were able to tap into in the form of roots, starchy vegetables, and seeds."
The findings are the result of a seven-year study conducted by more than 50 foreign scientists and published on Monday in the Proceedings of the National Academy of Sciences. Researchers recreated the oral microbiomes of Neanderthals, primates, and humans, including what is thought to be the oldest oral microbiome ever sequenced: a 100,000-year-old Neanderthal.
The goal was to learn more about the evolution of the oral microbiome, which is a community of microorganisms found in our mouths that help to protect against disease and promote health.
The researchers compared the fossilized dental plaques of modern humans and Neanderthals to those of humanity's nearest primate relatives, chimps and gorillas, as well as howler monkeys, a more distant relative.
The findings also push back on the idea that Neanderthals were top carnivores, given that the "brain requires glucose as a nutrient source and meat alone is not a sufficient source," Warinner said.
According to the researchers, the discovery makes sense because starch-rich foods, such as underground roots, tubers (like potatoes), and forbs, as well as nuts and seeds, are important and reliable protein sources for hunter-gatherer societies around the world.
In reality, starch now accounts for roughly 60% of all calories consumed by humans worldwide.
"It shows that our microbiome encodes valuable information about our own evolution that sometimes gives us hints at things that otherwise leave no traces at all," Warinner said.