WEDNESDAY, May 12, 2021 (HealthDay News) – Not only have humans and their ancestors been eating carbohydrates for longer than expected, but a new study finds that these starches may have played a role in the growth of the human brain. .
A new study into the history of the human oral microbiome has found that Neanderthals and ancient humans adapted to consuming starchy foods 100,000 years ago, which is much earlier than previously thought.
“We think we’re seeing evidence of a really ancient behavior that could have been in part encephalization – or the growth of the human brain,” said researcher Christina Warinner, of Harvard University. “This is proof of a new food source that early humans were able to draw upon in the form of roots, starchy vegetables and seeds.”
The oral microbiome is a community of microorganisms in the mouth. They help protect against disease and promote health.
The findings are part of a seven-year study that involved the collaboration of more than 50 international scientists.
They reconstructed the oral microbiomes of Neanderthals, primates, and humans, including a 100,000-year-old Neanderthal, in what is believed to be the oldest oral microbiome ever to be sequenced.
Scientists analyzed fossilized dental plaque from modern humans and Neanderthals, then compared it to chimpanzees and gorillas, the closest relatives of human primates, and howler apes, a more distant relative.
Billions of DNA fragments preserved in the fossilized plaque have been genetically analyzed to reconstruct their genomes.
Researchers were surprised to find strains of oral bacteria specially adapted to break down starch. These bacteria, of the genus Streptococcus, have a unique ability to capture starch-digesting enzymes from human saliva and provide nourishment. The genetic machinery they use to do this is only active when starch is part of the normal diet.
Neanderthals and ancient humans had these starch-adapted strains in their dental plaque, but most primates had almost none.
“It seems that this is a very human specific evolutionary trait that our Streptococcus has acquired the ability to do so, ”Warinner said in a Harvard press release.
The results were published on May 10 in the Proceedings of the National Academy of Sciences.
The researchers said the discovery made sense because for hunter-gatherer societies around the world, starchy foods such as underground roots, tubers like potatoes, and nuts, and seeds were nutritional sources. important and reliable.
The human brain needs glucose for a source of nutrients, and meat alone is not enough, Warinner said. Starch makes up about 60% of human calories worldwide.
“Its availability is much more predictable throughout the annual season for tropical hunter-gatherers,” said study co-author Richard Wrangham, Ruth B. Moore professor of biological anthropology at Harvard. “This new data makes sense to me, reinforcing the more recent view of Neanderthals that their diet was more like a sapien diet than previously thought,” [meaning] rich in starch and cooked. “
The research also identified 10 groups of bacteria that have been part of the human and primate oral microbiome for over 40 million years and are still shared today. Relatively little is known about them.
The oral microbiome of Neanderthals and humans today was almost indistinguishable. The study touches on the power to analyze the tiny microbes that live in the human body.
“It shows that our microbiome encodes valuable information about our own evolution that sometimes gives us clues about things that otherwise leave no trace,” Warinner said.
The Smithsonian National Museum of Natural History has more on ancient tools and food.
SOURCE: Harvard University, press release, May 10, 2021
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