Scientists discovered that the bacteria we carry in our intestines existed long before the humans evolved as a separate species.
The results of the experiment show that the gut bacteria had been determined by our evolutionary history. Factors like geography, diet, and medicine were also involved in the process.
The Gut Bacteria Study
The research involved the analysis of gut bacteria in humans and primates. For this, the scientists analyzed fecal samples taken from Congolese bonobos, Tanzanian chimps, Cameroonian gorillas, and compared them with samples from Connecticut human individuals.
The bacteria undertook genetic testing which had shown three different groups of bacteria that are commonly found in the human intestines. These groups cover up for 20% of the entire microbe population in the gut.
The three groups are Bacteroidaceae, Bifidobacteriaceae and Lachnospiraceae. The last group is present in both human and mammal gut flora, and its role is to protect humans from colon cancer. They are also believed to cause obesity.
In the present study, researchers looked into a specific gene that mimics the human species evolution, as it shows that the bacteria split in two species when the human ancestors did the same, over 15 million of years ago.
The gyrase is an enzyme that produces a negative supercoiling of the DNA. Researchers used this genetic marker to determine the common ancestors for gut bacteria in humans and in apes. Their analysis revealed that indeed, our gut bacteria evolution mimics the evolution of our species.
Evolutionary Biology
Ever since the bacteria species became separated, they evolved completely different in humans and in primates, as they had a different environment to adapt to.
The researchers managed to set a date for the moment of the split. When compared to chimps, the date should be around 5.3 million years ago. If compared with gorilla, the human bacteria started to separate 15.6 million years ago.
The scientists still do not know why the chimps and not the gorillas seemed to be similar to humans. However, they tend to believe that the bacteria diversified along with the hominid evolution.
The bacteria had not been just taken over from the environment and adapted to the human gut needs, but it evolved together with our species, managing to shape our immune system and our evolution as humans.
In the future, the scientist will want to continue the line of research by trying to reconstruct the history of human migration based on gut bacteria analysis, just like other teams of researchers study the human genome to determine the connections between the known groups of ancient people.
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