Two communities separated by thousands of miles, an ocean, and vastly different ways of life carry surprisingly similar bacterial populations in their digestive tracts, according to a new study published in the journal *Nature*. The research compares the gut microbiomes of the Hadza, hunter-gatherers who have inhabited northern Tanzania for millennia, with those of the Tsimane, an Indigenous group in the Bolivian Amazon who sustain themselves through foraging, fishing, hunting, and small-scale farming. Despite living on different continents and eating different diets, the two groups harbor microbial communities that share remarkable features, a finding that researchers say sheds light on how gut bacteria have traveled with humans across the globe.
The Hadza have roamed the savanna and woodlands of northern Tanzania for thousands of years, living a traditional foraging lifestyle that predates agriculture. The Tsimane, by contrast, live roughly 7,000 miles away in the lowland forests of Bolivia, where they combine hunting and fishing with horticulture, cultivating crops such as manioc. On the surface, the two populations appear to have little in common beyond their rural, non-industrialized ways of life. Yet the new study indicates that the bacterial ecosystems inside their bodies are far more alike than anyone might expect, suggesting that shared evolutionary history and traditional diets shape the gut in ways that modern urban living has largely erased.
The research carries implications that extend well beyond cataloging which microbes live where. Scientists increasingly view the gut microbiome as a crucial factor in human health, influencing everything from digestion and immune function to metabolism and resistance to disease. Understanding what a "healthy" microbiome looks like in populations that have not adopted industrialized diets and lifestyles could help explain why certain chronic conditions are rare in such groups and common elsewhere. The findings also raise the possibility that modern hygiene, processed food, and antibiotic use have depleted bacterial diversity in ways that may carry health consequences.
The study adds to a growing body of research suggesting that the microbes living inside humans have followed their hosts on migratory journeys across continents. As ancient humans spread out of Africa and populated the rest of the world, they carried their gut bacteria with them. Over time, those microbial communities evolved alongside their human hosts, adapting to local diets and environments. The new paper offers evidence that some of these ancient microbial lineages persist in traditional communities today, even in groups that have been separated geographically for thousands of years.
For years, scientists have puzzled over how industrialization has transformed the human microbiome. People living in urban, industrialized societies tend to have less diverse gut bacteria than those in traditional communities. This loss of diversity has been linked in some studies to rising rates of allergies, autoimmune disorders, obesity, and other conditions tied to inflammation. The Hadza and Tsimane, who maintain lifestyles closer to those of ancient humans, provide a window into what the microbiome may have looked like before agriculture, urbanization, and modern medicine reshaped it.
The Hadza have long been a focus of microbiome research. Previous studies have documented that their gut bacteria fluctuate with the seasons, shifting as their diet changes from berries and honey to meat and tubers depending on what the landscape provides. This flexibility reflects a microbiome adapted to a varied, unpredictable food supply, quite different from the stable, highly processed diets common in wealthy nations. The new study builds on that work by placing the Hadza alongside the Tsimane, another population that has preserved a traditional way of life despite increasing contact with the outside world.
The Tsimane have also drawn scientific attention for their unusually good cardiovascular health in old age, a finding that researchers have attributed in part to their active lifestyle and diet rich in fiber and lean protein. The new research suggests that their gut bacteria may contribute to these health advantages as well. By comparing the microbial communities of the two groups, the study authors hope to identify which bacteria are most important for maintaining health and which have been lost in industrialized populations. Such insights could eventually inform treatments or dietary recommendations aimed at restoring beneficial microbes.
Experts say the findings underscore the value of studying diverse human populations rather than relying solely on samples from Europe and North America. Much of what scientists know about the microbiome comes from studies of people in industrialized countries, which represent only a fraction of human genetic and cultural diversity. By including communities like the Hadza and Tsimane, researchers gain a more complete picture of the range of microbial variation and the factors that drive it. The new paper in *Nature* is part of a broader effort to map the global diversity of the human microbiome before traditional lifestyles disappear.
The study also raises questions about what happens when traditional communities adopt modern ways of living. As the Hadza and Tsimane face increasing pressure from land development, tourism, and globalization, their diets and daily habits are changing. Researchers warn that such transitions may come with a cost to gut health, as microbial diversity declines and bacteria adapted to traditional foods are lost. Documenting the microbiomes of these groups now may be essential for understanding what is being lost and for developing strategies to preserve beneficial bacteria.
The similarities between the Hadza and Tsimane microbiomes suggest that certain bacteria are deeply rooted in the human lineage, passed down and maintained across vast distances and long periods of time. The study's authors argue that these shared microbes likely played important roles in human evolution, helping early people extract nutrients from a wide range of plant and animal foods. If those bacteria are missing from modern guts, it could help explain why so many people in industrialized societies suffer from digestive and metabolic disorders that were once rare.
Taken together, the new research paints a picture of the gut microbiome as a dynamic, inherited ecosystem that has co-evolved with humans for millennia. The Hadza and Tsimane, though separated by an ocean, preserve microbial communities that echo this shared past. As scientists continue to explore the links between gut bacteria and health, studies like this one highlight the importance of understanding where these microbes came from, how they have changed, and what their loss may mean for human well-being in the modern world.
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