Neanderthals Ate Carbs Too, Fossil Plaque Study Finds

Eating starch apparently goes back a lot further than we thought, predating humankind, But why did Neanderthals and humans have the same mouth bacteria – until the Late Stone Age?

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A primeval caveman holding a bone and hitting a rock with it.
Neanderthal at a meal: There aren't any illustrations of a Neanderthal eating rootsCredit: Di Gorodenkoff /

Just how much meat did Neanderthals eat? Perhaps not as much as we thought. A new study claims that, just like us, our cousins the Neanderthals ate starchy foods too. That had not necessarily been expected.

The Homo line took a sharp turn to carnivorousness at least 2 million years ago, recent research has concluded. That’s well before Neanderthals and Homo sapiens even began to evolve. So both of us, Neanderthals and sapiens, would have evolved from an ancestor with a heavy meat habit.

Unlike cats, the human line cannot subsist chiefly on protein. Our livers can’t cope. Hence in the pre-agricultural era, animal fat was a crucial component of the archaic diet, leading to the theory that the archaic humans hunted chiefly the biggest animals, which had the most alluring layers of fat. When the mega-fauna were gone, whether because we hunted them to extinction or because of other adaptability issues, our ancestors had to resort to smaller animals and other foods.

The question is, which other foods? In the Homo sapiens’ case, we’re clear that we subsisted on hunting and gathering all sorts of things – roots, berries, nuts ... if it didn’t eat us first, we ate it. But in the case of our cousins the Neanderthals, we didn’t necessarily assume the same. One study in 2016 even postulated that the barrel-shaped torso of the Neanderthal attested to liver enlargement in order to cope with a heavy meat diet.

However, another analysis based on fossil feces 50,000 years old found in Spain, and believed to have been deposited by Neanderthals, showed that they ate meat, and also roots, berries and nuts.

Now, a new study involving work by more than 50 scientists around the world posits that not only Neanderthals and fairly early humans were eating starch-rich foods as long as 100,000 years ago.

Until now, Neanderthals hadn’t been thought to eat carbs at all, and it had been thought that humans realized the charms of starch mainly after the Neolithic revolution and discovery of agriculture. The study was published by Prof. Christina Warinner of Harvard, with colleagues, in the Proceedings of the National Academy of Sciences this week.

Actually, what they set out to elucidate is the evolutionary history of oral bacteria in the hominin line: the oral biome. They did this by identifying bacteria in dental calculus on the teeth of Neanderthals and ancient modern humans, contemporary humans, and comparing the results with bacteria in the plaque on the teeth of great apes, and howler monkeys while about it. The Neanderthal’s plaque studied in this paper was 100,000 years old.

Given that Neanderthals and Homo sapiens both ate carbs, maybe their common ancestor did too? It isn’t case closed, but it’s a possibility.

How they identified the bacteria is interesting too: Using cutting-edge techniques, they sequenced billions of DNA fragments preserved in the fossilized plaque to reconstruct the bacterial genomes. “It’s similar in theory to how archaeologists painstakingly piece together ancient broken pots, but on a much larger scale,” the team explains.

The tuber harvest from one Yacón plant.Credit: Farmcore

They’re using your enzymes

And what did they find? They discovered 10 groups of bacteria that had been maintained throughout African hominid evolution, and were also found in the howler monkeys. We have, apparently, been orally harboring these microbes since before the catarrhine-platyrrhine split about 40 million years ago.

For all that they have been living in our ora for 40 million years, we know “relatively little” about them, the team confesses, adding, “Some don’t even have names.”

Zeroing in closer, the team found major differences in the species and function of the mouth bacteria between the Homo line and chimpanzees; and they found a high degree of similarity between Neanderthals and modern humans. That could indicate shared adaptations in nutrient metabolism.

The biggest surprise from the study, the authors share, was the discovery in Neanderthals and humans of particular strains of streptococci specially adapted to break down starch.

The other primates have almost none of this bacteria, which “capture” starch-digesting enzymes from human saliva! that they then use to feed themselves. Wondrous are the ways of nature.

“The genetic machinery the bacteria uses to do this is only active when starch is part of the regular diet,” the team writes. So first of all this delightful microbe seems to have evolved together with our diet; which indicates we and the Neanderthals ate starch while other primates didn’t.

“It seems to be a very human specific evolutionary trait that our Streptococcus acquired the ability to do this,” Warinner said.

(There are dozens of streptococci species; only a handful cause disease in humans.)

In addition, the researchers detected genetic diversity in the oral bacteria of Neanderthal and late Stone Age modern humans that was not observed in later modern human populations.

A sample of clonally propagated mashua cultivars, in Peru.Credit: Michael Hermann

Get smart

What can we learn from all this? Possibly what a normal healthy microbiome is, Warinner suggests. “If we only have people today that we’re analyzing from completely industrialized contexts and that already have high disease burdens, is that healthy and normal? We started to ask: What are the core members of the microbiome? Which species and groups of bacteria have actually co-evolved with us the longest?” Now we know.

What might this addition of starch to our diet have done for us evolutionarily?

One question is when the carb habit, flooding our bodies with glucose, began. “We think we’re seeing evidence of a really ancient behavior that might have been part encephalization – or the growth of the human brain,” Warinner explained. The microbiome data indicates that early humans had discovered a new food source: roots, starchy vegetables, and seeds.

The expansion into starch could have driven the expansion of the human brain because what is starch, anyway? It breaks down into glucose, which, the authors point out, is the brain’s main fuel source.

By the way, illustrating the importance of dietary diversity, since they couldn’t survive on nothing but meat and fat of marine mammals and fish, paleo-Eskimos in Siberia would also eat the stomach contents of the herbivores they hunted.

At this point in our evolution, starch makes up about 60 percent of the calories we eat today. It bears adding that starch is found not only in potatoes but in nuts, seeds and forbs – grasses such as sedge, which we used to eat.

Key here: used to eat. The researchers were surprised to find that the Neanderthal and Late Stone Age modern human’s oral microbial world were “almost indistinguishable,” with differences only when analyzing individual bacterial strains.

Late Stone Age humans in Europe over 14,000 years ago, at the tail end of the Ice Age, shared some bacterial strains with Neanderthals that are no longer found in humans today, the team writes.

Among other things, the shared microbiome supports the growing body of evidence for admixture between Neanderthals and modern humans, in Europe and the Middle East. And then what happened?

Our diet changed profoundly during the Holocene. Hunting and gathering would give way to agriculture and animal husbandry, at different times in different places, but all after the Ice Age began to retreat. Some think it’s because we basically had no choice but to domesticate herbivores, having hunted the large animals (with the help of dogs!) to the point of desperation or extinction.

In Mesopotamia, for instance, grains and the core domestication animals (cows, sheep, goats) were by and large being domesticated around 10,000 years ago, giving a millennia here or there. Some of the assumptions we make have been refined or debunked by research, one being that the transition from a strenuous, spare existence hunting and gathering nuts and berries, etc, to settling down and eating grains and breads made us sicker. Not necessarily so, one study from Vietnam and Cambodia found – it just changed our disease burden

And no, it isn’t necessarily true that we had gorgeous pearly whites when we were hassling mammoths on the tundra, or that the addition of naturally occurring starches rotted our teeth. Separate research indicates that naturally occurring starches don’t necessarily drive dental caries, while processed simple sugars do