A new study published in the journal *Nature* has found that two Indigenous communities separated by thousands of miles and living vastly different lifestyles nevertheless share significant similarities in the bacteria residing in their guts. The research, reported by NPR, examined the Hadza people of northern Tanzania and the Tsimane people of the Bolivian Amazon, offering fresh clues about how the human microbiome may have evolved alongside our species as people migrated across continents.
The Hadza are hunter-gatherers who have roamed northern Tanzania for thousands of years. Their way of life, centered on foraging for wild plants and hunting game, is often studied by scientists as a window into how humans lived before the rise of agriculture. The Tsimane, by contrast, are an Indigenous population in the Bolivian Amazon who subsist through a mix of foraging, fishing, and hunting, along with small-scale horticulture. Roughly 7,000 miles separate the two groups.
On the surface, these rural communities would appear to have little in common. They inhabit different continents, speak different languages, and confront different environments. Yet the new study shows that when it comes to the trillions of microorganisms living in their digestive tracts, the two groups display remarkable parallels.
The findings add to a growing body of research suggesting that the gut microbiome—the diverse community of bacteria and other microbes that help digest food, train the immune system, and influence overall health—is not merely a product of modern diet and environment. Instead, it may carry signatures of ancient human history, shaped over millennia as populations moved and adapted to new landscapes.
Scientists have long been interested in the microbiomes of communities that maintain traditional, non-industrialized lifestyles. Because these groups eat diets rich in fiber, fermented foods, and wild plants, and because they are less exposed to antibiotics and processed foods, their gut bacteria often look quite different from those of people in industrialized nations. Studying them can help researchers understand what a "healthy" microbiome might have looked like before modernization.
The comparison between the Hadza and the Tsimane is particularly compelling because the two groups practice different subsistence strategies. The Hadza rely almost entirely on hunting and gathering, while the Tsimane combine foraging with horticulture—growing crops such as manioc, which they also use to brew a local fermented drink. Despite these differences, the study found surprising overlap in their gut bacterial communities.
Experts say the paper's implications extend beyond the two communities themselves. If distantly related populations share microbial traits, those traits may have been inherited from a common ancestral human microbiome—one that traveled with people as they spread out of Africa and across the globe tens of thousands of years ago. In other words, gut microbes may themselves be migrants, carried along by their human hosts.
The research also raises important questions about the role these bacteria play in human health. Many chronic conditions common in wealthy countries—including obesity, allergies, inflammatory bowel disease, and autoimmune disorders—have been linked to alterations in the gut microbiome. By comparing traditional and industrialized populations, scientists hope to pinpoint which microbial changes matter most for health.
For the Hadza and the Tsimane, maintaining traditional diets appears to support a diverse and resilient gut ecosystem. However, both communities are increasingly exposed to outside influences, from market foods to antibiotics, which could reshape their microbiomes in the years ahead. Researchers note that documenting these communities' microbial diversity now is a race against time.
The study also underscores the value of cross-cultural collaboration in science. Researchers working with the Hadza and the Tsimane rely on long-term relationships with these communities, whose members participate voluntarily in health and biological studies. Such partnerships have yielded insights not only into the microbiome but also into aging, cardiovascular health, and infectious disease.
While the new paper does not settle every question, it strengthens the case that the human relationship with gut microbes is ancient, dynamic, and deeply intertwined with our species' wanderings. As people moved across continents, they carried not only their genes and cultures but also a living community of bacteria inside them.
Future research is expected to explore how specific microbial strains differ between populations and whether those differences can be traced to particular migrations or dietary adaptations. Scientists may also investigate whether certain gut bacteria have co-evolved with humans to perform essential functions, such as breaking down fibrous plant material or producing vitamins.
Ultimately, the study suggests that understanding the microbiome requires thinking about human history on a grand scale. The bacteria in our guts are not just passengers; they are companions that have followed humanity on its long journey across the planet. For researchers, that insight could reshape how they approach everything from nutrition to medicine.
The new findings, published in *Nature*, offer a reminder that even communities living worlds apart can be connected in ways invisible to the naked eye. In the gut, at least, the distance between Tanzania and Bolivia may be far smaller than it appears.
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