gut microbiome – A study suggests that gut microbes have been passed down through human generations for millennia, raising questions about what we lose in modern life.
Thousands of miles and an ocean separate the Hadza people. who have roamed northern Tanzania for generations. from the indigenous Tsimane community in the Bolivian Amazon. Yet. despite these vast distances and vastly different diets. a new study reveals a startling. invisible thread connecting them: their gut microbiomes are nearly identical.
Researchers found that these two rural communities share roughly 1,200 of the same bacterial species—a 90% overlap in their microbial makeup. For scientists, this isn’t just a curiosity of biology. It suggests that these bacterial strains didn’t simply appear by chance; they have been hitchhiking alongside human populations for tens of thousands of years. passed down through generations as our ancestors migrated across the globe.
The findings, published in the journal Nature, indicate that this microbial kinship likely took shape long before human migration diverged. Using dating techniques based on how rapidly bacteria change. researchers determined that many of these microbial strains share a common ancestor from approximately 17. 000 years ago. if not earlier. It appears these bacteria traveled with humans as they moved through Eurasia. crossed the ancient land bridge connecting Russia to Alaska. and eventually settled in South America.
For Justin Sonnenburg. a professor of microbiology and immunology at Stanford University and the study’s senior author. the discovery highlights a fundamental disconnect in the modern world. “If we were inhabited by very similar microbes over a long period of time. it suggests that our human genomes may have come to expect a certain set of microbes and functions. ” Sonnenburg explains. He notes that roughly 60% of the microbes shared by the Hadza and Tsimane are rare or entirely absent in people living industrialized. urban lives. “When you start to lose biodiversity in your gut. there may be big issues for your human biology to adjust to and accommodate.”.
This shift away from ancestral bacteria is a hallmark of modern living. where microbiomes are often products of current lifestyle and local interactions rather than hereditary transmission. As babies are born with a blank slate. they typically acquire their microbes from their mother’s vaginal canal and skin. followed by household and community exposure through the fecal-oral route—a process where microscopic particles. a micron or less in length. are passed through air and dust.
While the theory is compelling, it remains an emerging area of study. Andrew Moeller. an associate professor of evolutionary biology at Princeton University. notes that while the findings are intriguing. it is not yet proven that the loss of these ancestral strains is inherently deleterious. “Another alternative is that the industrialized microbiome profile may actually be adapted to an industrialized lifestyle,” Moeller says. “From a health perspective, is it good or deleterious that industrialized humans have lost a lot of ancestral microbial taxa?. We actually don’t know.”.
Taichi Suzuki. an assistant professor at Arizona State University. points out that the potential risks of this “mismatch” are already visible in some areas of medicine. For instance. he cites how individuals with African ancestry often face a lower risk of serious illness from a specific African strain of H. pylori, likely because their genomes evolved in tandem with the bacteria—a protective evolutionary history that others may lack.
As the scientific community works to parse which of these lost microbes might be beneficial to regain. the study underscores that our internal biology is far more than a simple reaction to what we eat today. It is a living history. one that suggests we have carried these tiny. essential partners with us since long before the land bridges vanished and the modern world took its current shape.
microbiome gut health human evolution Hadza Tsimane biology science research health