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They reveal the evolutionary history of the bacteria in our mouth

The plates on our teeth contain surprising clues about the evolution of the first hominids and our own health. In this way, our oral microbiome, which is made up of trillions of microbial cells belonging to thousands of bacterial species, has evolved together with us over millions of years. However, we still know very little about him.

Scientists from more than 40 institutions in 13 countries have studied the fossilized dental plaque of humans and Neanderthals to learn the evolutionary history of the hominin oral microbiome over the last 100,000 years. Likewise, he has compared these remains with that of chimpanzees, gorillas and howler monkeys. The results are published in the journal PNAS.

The study of the microbiome through metagenomics is a fundamental task to understand the evolution of our species and the functioning of our body

James Fellows Yates

“The study of the microbiome through metagenomics is a fundamental task to understand the evolution of our species and the functioning of our body,” he tells SINC James Fellows Yates, researcher of the Max Planck Institute for History of Science in Germany, which leads this work in which several Spanish research centers also participate.

According to the authors, this work highlights the value of investigating ancient oral metagenomes to reveal key insights into major events in modern human evolution and prehistory.

“A metagenome corresponds to the total genetic content of a sample. Not just the DNA of the host, but also of all the microbes that live in the body – the human microbiome. This is considered as important for human health as a vital organ such as the heart or lungs, since maintaining a healthy set of microbes means that we maintain our own body ”, emphasizes the scientist.

In total, they analyzed 124 fossil remains which revealed 10 bacterial genera that have persisted throughout the evolution of African hominins and are also shared with howler monkeys. This fact suggests that these microbial groups could have played a key role in dental plaques for more than 40 million years.

A metagenome corresponds to the total genetic content of a sample. Not just the DNA of the host, but also of all the microbes that live in the body – the human microbiome.

James Fellows Yates

Likewise, the authors found important differences in Homo bacteria and chimpanzees, but striking similarities between those of the chimpanzees. neanderthals and modern humans. In fact, oral bacteria modern humans and Neanderthals are almost indistinguishable.

“That these bacteria in our mouths and theirs are so similar supports the evidence that we have had a very long and close relationship with them,” adds Fellows Yates.

Consumption of foods rich in starch

The most striking thing about this finding is that they have discovered a group of bacteria, present in both modern humans and Neanderthals, that are specially adapted to consume starch.

“Unlike non-human primates, Homo is characterized by the abundance of species of Streptococcus which can produce proteins that bind to the enzyme amylase, which helps convert the starch in sugars. This finding suggests that these microbes adapted to starch-rich diets early in human evolution, “the researchers note.

This finding suggests that these microbes adapted to starch-rich diets early in human evolution.

James Fellows Yates

However, they also found some small differences, such as that ancient humans who lived in the Europe of the Ice Age they shared some bacterial strains with Neanderthals, although these strains are no longer present in humans today.

“The study uses the starchy foods referred to as ‘underground storage organs’ (USOs) that were consumed by early hominins, that is, starchy tubers such as yams in Africa,” explains the investigator.

Starchy foods, such as roots, tubers and seedsThey are rich sources of energy, and it had been argued that the passage of our ancestors to the consumption of these foods may have been what allowed humans to develop the large brains that characterize our species.

“Analyze not only the host geneticsBut perhaps also the genetics of the bacteria in our human microbiome will help determine exactly when these adaptations occurred, ”says Fellows Yates.

The Spanish contribution to the study

The so-called “Red Lady” of the Cueva del Mirón, in Ramales de la Victoria (Spain), a Magdalenian woman of about 19,000 years ago, is part of this study, as the only representative of the European Upper Paleolithic populations.

Of the nine new Neanderthal sites in the European Middle Palaeolithic In this study, five are in Spain: Banyoles, La Güelga, Cueva de Valdegoba, Cueva del Boquete de Zafarraya, and Sima de las Palomas del Cabezo Gordo. In addition, four individuals from the El Collado site as representatives of the Mesolithic period of the Iberian Peninsula.

Like archaeologists reconstructing broken vessels, archaeologists also have to painstakingly piece together broken fragments of ancient genomes to reconstruct a complete picture of the past.

“Working with DNA that is so ancient is a great challenge and, like archaeologists reconstructing broken vessels, archaeogeneticists they also have to painstakingly piece together the broken fragments of ancient genomes to reconstruct a complete picture of the past. To achieve this, we have developed new tools and analyzes to genetically characterize billions of DNA fragments in order to identify the bacteria –dead for a long time –which are conserved in the archaeological record ”, they conclude.

Reference:

James Fellows Yates et al. “The evolution and changing ecology of the African hominid oral microbiome”, PNAS.

Fountain: SINC

Rights: Creative Commons.

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