Modern human oral microbiome contains about 700 species of unicellular organisms that are responsible for our health. However, thousands of years ago, when our civilization was younger, the human mouth was a completely different and much more habitable environment - the majority of the most common modern tooth defects were unknown to Bronze Age people.
Scientists from Trinity College Dublin researched two teeth from a male individual who lived about 4000 years ago to find out how and why the human microbiome changed through epochs.
Cavities' ancestors
During the study, scientists searched for Streptococcus mutans, a specific bacteria causing tooth cavities in the modern world. However, in ancient times Streptococcus mutans was a "strange beast" among humans that rarely appeared in the Bronze Age population's mouths because of the lack of favorable habitats - the sugar-containing environment.
The first dramatic "boom" of dental cavities happened after the sugary meal became widespread among the population (about 3500-3000 years ago).
What have scientists found?
Considering the nature of the 'cavity bacteria', described above, scientists were quite surprised when they observed its abundance on the sampled tooth. Moreover, researchers discovered that other species of Streptococcus, specific to ancient people's oral microbiomes, were absent from the tooth, which means that the mutans species had outcompeted them, significantly changing the balance of the oral microbiome in the organism of ancient person.
Also, in the sampled tooth, scientists found two very different strains of Tannerella forsythia - bacteria causing gum disease (for now, only one linage of forsythia is dominant in human oral microbiomes)
What does it mean?
Results of the scientific research shed light on the biological history of the existing oral pathogenes causing the most common disorders like cavities or gum disease. And, what is more important, these results may support the hypothesis of a "disappearing microbiome," which means that our modern oral microbiomes are less diverse than ancient humans had.
However, such conclusions contradict the medical fact that poor biodiversity of the microbiome can affect human health.
Also, the researched evolution of described ancient pathogens showed that technical progress and changes in human ration had significantly affected the population and diversity of microbes in our moth.
