New research examining bacteria collected from Neanderthal teeth suggests that our hominid cousins’ diets were heavy on roots, nuts and other starchy, carbohydrate-rich foods at least 100,000 years ago, reports Ann Gibbons for Science. Shifting to eating high-calorie starches as a dietary staple may have been essential for fueling the evolution of our large human brains, and this study pushes back the earliest evidence of that shift.
“We think we’re seeing evidence of a really ancient behavior that might have been part of encephalization—or the growth of the human brain,” says Christina Warinner, an anthropologist at Harvard University and co-author of the research, in a statement. “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.”
Human mouths are full of bacteria, and when plaque-causing bacteria on teeth form hard patches of tartar or calculus, that material can be studied by scientists. Warinner tells Ellie Shechet of Popular Science these mineralized patches can persist for millennia and provide a record of which bacteria formed the tartar in the first place, even on ancient fossil teeth.
The study, published this week in the journal the Proceedings of the National Academy of Sciences, analyzed the traces of bacterial DNA found on the teeth of Neanderthals, modern humans, chimpanzees, gorillas, and howler monkeys. Researchers found the entire group, made up of 124 individuals, shared a core of ten types of bacteria that might have taken up residence in the mouths of human’s ape ancestors some 40 million years ago.
But there was one type of bacteria that was only common in the teeth of humans and Neanderthals: Streptococcus. Bacteria in this genus are involved in converting starches into sugars and finding them all over human and Neanderthal teeth suggests that starches were a big part of their respective diets.
The oldest Neanderthal tooth in the study came from an individual that lived 100,000 years ago, so the findings push the dietary shift to carbohydrate-heavy foods back to at least that long ago. But, according to Science, humans and Neanderthals would have likely inherited their oral microbiomes, and the Streptococcus bacteria, from their last common ancestor roughly 600,000 years ago. Warinner tells Science that this pushes the timeline back even further—between 700,000 and 2 million years ago—to when our shared ancestors' brains were growing larger under the pressures of evolution.
“These starch and sugar-rich diets allowed hominids to have a bigger brain and evolve as we have,” James Fellows Yates, a molecular anthropologist at the Max Planck Institute, tells Kaitlin Sullivan of Inverse.
Finding Streptococcus bacteria in the mouths of ancient humans and Neanderthals also suggests cooking may have been common even earlier than previously thought and long before the advent of agriculture. Per Science, that’s because Streptococcus rely on an enzyme called amylase to break down starches into sugars, and this enzyme works best on starches that have been cooked.
Looking toward the present, Warinner tells Popular Science that getting to know the oral bacteria our species has in common with our ancestors could also help us take better care of our mouths today.
“I think this is a really exciting opportunity in microbiology to understand what these bacteria are and do and why they seem to be conserved in our mouths for over 40 million years of evolution,” Warinner tells Popular Science. “They might be a key to understanding oral and dental health.”