Scientists from the University of California, Santa Barbara, and Stanford University have found that two geographically separated populations—the forager-farmer Tsimané of lowland Bolivia and the hunter-gatherer Hadza of Tanzania—share more than 1,200 bacterial species in their gut microbiomes. The discovery, announced by UCSB, suggests that a core set of microbes may have accompanied human ancestors as they migrated around the world.
The finding surprised researchers because the two groups eat very different diets. The Hadza consume mammals, birds, fish, and foraged fruits and vegetables, while the Tsimané rely more on fiber-rich plantains, rice, manioc root, and corn, along with fish, peccary, and other mammals. Despite these differences, their gut microbiomes are highly diverse and remarkably similar.
More than 60 percent of the shared bacterial species are rare or absent in the microbiomes of people living in industrialized populations. This pattern suggests that modern lifestyles, including processed diets and antibiotic use, may have reduced the diversity of gut bacteria in industrialized societies.
«That made us wonder if there really is a core set of bacterial and other species that traveled with the ancestors of the Tsimané as they migrated around the globe,» said Benjamin Good of Stanford University.
To investigate, the researchers identified genetic signatures in the bacterial DNA of both populations and used mutation rates to estimate when bacterial species diverged from a common ancestor thousands of years ago. The analysis provided strong evidence that the ancestors of both groups—and presumably all humans—harbored these same bacteria long ago.
«The analysis shows strong evidence that their ancestors, and presumably all of us, had these same bacteria long ago,» said Michael Gurven of UCSB.
The study, published in the journal Nature, adds to growing evidence that the human gut microbiome has changed dramatically with industrialization. The researchers note that the shared microbes may have played important roles in human health for millennia, and their loss could have implications for immune function and metabolism.
The Tsimané and Hadza are among the few remaining populations that maintain traditional subsistence lifestyles, making them valuable for understanding the ancestral human microbiome. However, both groups are increasingly exposed to outside influences, and researchers caution that these microbial communities may be changing.
The findings raise questions about whether industrialized populations could benefit from restoring some of these lost bacteria, though the researchers emphasize that much more work is needed before any clinical applications. The study also highlights the importance of preserving microbial diversity as part of global biodiversity.
According to the statement, the research was conducted by scientists from UCSB and Stanford University. The original scholarly article appears in Nature.
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