Two communities separated by thousands of miles and vastly different ecosystems may share more than researchers previously realized—at least when it comes to the microscopic organisms living inside their digestive tracts. A new study published in the journal *Nature* has documented remarkable similarities between the gut microbiomes of the Hadza people of northern Tanzania and the Tsimane people of the Bolivian Amazon, suggesting that these bacterial communities may have traveled alongside humans as they migrated across continents over millennia.
The Hadza are among the world's few remaining hunter-gatherer populations, having inhabited the savanna and woodlands of northern Tanzania for thousands of years. They sustain themselves by hunting game, gathering wild plants, and collecting honey. The Tsimane, meanwhile, live in the rainforests of the Bolivian Amazon, where they practice a mix of foraging, fishing, hunting, and small-scale horticulture. Despite these differences in lifestyle and environment, the bacteria residing in their guts appear strikingly alike.
The research, reported by NPR, represents a significant contribution to the growing field of microbiome science—the study of the trillions of bacteria, viruses, fungi, and other microorganisms that inhabit the human body. Most of these microbes live in the intestines, where they play critical roles in digestion, immune function, and overall health. Understanding how these communities differ across human populations could illuminate how modern lifestyles have altered our internal ecosystems.
Scientists have long been interested in the gut microbiomes of traditional populations because they offer a window into what human bacterial communities might have looked like before industrialization, processed foods, antibiotics, and urban living dramatically reshaped them. Studies of groups like the Hadza have shown that their gut microbiomes tend to be far more diverse than those of people living in industrialized societies—a diversity that many researchers believe is linked to better health outcomes.
The new paper builds on that foundation by comparing two geographically distant populations that share certain ancestral ways of life. The fact that the Hadza and Tsimane harbor similar bacterial communities despite living on different continents and eating different foods suggests that these microbial partnerships are ancient, likely established long before humans dispersed around the globe.
Experts say the findings hint at a deeper story about human evolution and migration. As ancient humans moved out of Africa and populated new landscapes, they likely carried their gut microbes with them. Over time, those microbes would have adapted to new diets and environments, but a core community may have persisted—a biological signature of shared ancestry.
The research also raises important questions about what has been lost in modern populations. In industrialized countries, gut microbiome diversity has plummeted, a decline that some scientists associate with rising rates of autoimmune disorders, allergies, obesity, and other chronic conditions. The similarities between the Hadza and Tsimane underscore how much the typical Western gut has diverged from its ancestral state.
The study's implications extend beyond evolutionary biology. If certain gut bacteria are indeed important for human health, understanding which microbes are common among traditional populations—and what they do—could inform new approaches to treating or preventing disease. However, researchers caution against oversimplifying the relationship between gut bacteria and health, noting that the microbiome is a complex, dynamic system influenced by diet, environment, genetics, and countless other factors.
The Hadza have been the subject of numerous microbiome studies in recent years, partly because their traditional lifestyle offers a rare glimpse into how humans lived for most of their evolutionary history. Their diet varies dramatically with the seasons, shifting between meat, honey, berries, and tubers depending on what is available. This cyclical pattern appears to influence their gut bacteria in ways that researchers are still working to understand.
The Tsimane have likewise drawn scientific attention for their unusually good cardiovascular health in older age, a finding that has prompted investigations into their diet and lifestyle. The new study adds another dimension to that research by examining their gut microbiomes alongside those of the Hadza. The image accompanying the NPR report showed a Tsimane extended family preparing for the morning, with a large pot of manioc roots cooking to make shocdye, a local fermented brew—a reminder that diet and fermentation practices shape gut bacteria in culturally specific ways.
For the general public, the study reinforces a growing awareness that the human body is not a solitary organism but a complex ecosystem. The microbes within us outnumber our own cells and carry out essential functions, from breaking down fiber to producing vitamins and training the immune system. Learning how these communities evolved and how they differ across populations could eventually lead to more personalized approaches to nutrition and medicine.
The research also highlights the importance of studying and preserving traditional ways of life—not only for cultural reasons but for scientific ones. As globalization and modernization reach even remote communities, the unique microbiomes of groups like the Hadza and Tsimane may change irreversibly. Scientists warn that once these microbial communities are lost or altered, the opportunity to study them in their original state may disappear.
In the end, the study offers a reminder that human history is written not only in our genes but also in the bacteria we carry. The microscopic passengers in our guts have accompanied us on our long journey across the planet, adapting and enduring alongside us. Understanding that partnership may shed light on how to keep modern humans healthy in a world that looks very different from the one our ancestors inhabited.
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