TL;DR
Turn your wind-down time into listening time
- Thousands of audiobooks, podcasts and originals
- Listen on your phone, tablet or Echo — also offline
- Cancel anytime
A study led by Stanford researchers found that the Hadza of Tanzania and the Tsimane of Bolivia share more than 1,200 gut bacterial species, many rare or absent in industrialized populations. Genetic analyses estimated that splits among some microbial strains date to periods of ancient human migration, though the findings do not establish that microbiome loss causes chronic disease.
A study published October 7 in Nature found that the Hadza of Tanzania and the Tsimane of Bolivia share more than 1,200 gut bacterial species, despite their populations having been geographically separated for tens of thousands of years. Genetic analyses by a Stanford University-led team suggest that some microbial lineages split around the periods of major human migrations, adding evidence that gut microbes with long evolutionary histories remain in populations with comparatively limited exposure to industrialization.
The researchers reported that the two groups shared 1,231 bacterial species, nearly 90% of the species identified in the Tsimane microbiomes. About 60% of the shared species were rare or completely absent in the industrialized populations used for comparison. These figures describe the study’s sampled microbiomes; they do not establish how common each species is in every member of either population.
To identify microbes and estimate their evolutionary histories, the team used deep metagenomic sequencing, which reads DNA from the organisms present in stool samples. The researchers applied several population-genetics methods to estimate when microbial strains separated. For many species, those estimates aligned with the broad time frame of prehistoric migrations out of Africa and into the Americas, according to the report.
The analysis drew on voluntarily provided Tsimane stool samples collected by the Tsimane Health and Life History Project, alongside Hadza samples sequenced in earlier work. The researchers said the higher-resolution sequencing enabled them to detect species that are difficult to capture when present in low abundance. The study compared microbial communities; it did not test whether losing particular microbes directly causes any specific illness.
What Ancient Microbes May Reveal
The findings provide a historical frame for research into microbiome diversity. Industrialized populations have been reported to have less diverse gut microbiomes than people living in less industrialized settings. Finding that many species shared by the Hadza and Tsimane are uncommon or missing in industrialized populations gives researchers a basis to investigate when that divergence occurred and which microbial lineages may have been lost.
Gut microbes are involved in functions including digesting fibrous foods, producing vitamins and training immune responses. The study’s authors argue that the long association between people and some microbial lineages makes their recent decline a relevant question for human biology. But the research does not show that the decline explains higher rates of autoimmune disease, Type 2 diabetes, obesity or other chronic conditions reported in industrialized societies. Those possible links remain unresolved, and the comparison cannot by itself separate the effects of microbes from diet, environment, lifestyle or other factors.
Popular right now
Vitamix Propel Series 510 Professional-Grade Blender, 3 Programs, Black
Breville BES870XL Barista Express Espresso Machine, Brushed Stainless Steel
KitchenAid Artisan Series 5-Quart Tilt-Head Stand Mixer, Dried Rose (KSM150PS)
As an affiliate, we earn on qualifying purchases.
Two Populations, Deep Histories
The study focused on the Hadza, a hunter-gatherer group, and the Tsimane, Indigenous forager-horticulturalists. Their food practices differ: Hadza diets include hunted animals and foraged plants, while the Tsimane grow foods such as plantains, rice, manioc and corn, alongside eating fish and forest animals. Their shared microbial species therefore surprised researchers, given both the dietary differences and the long geographic separation.
The new work builds on earlier sequencing. A 2023 study of Hadza samples reported an average of about 750 species per Hadza individual, compared with about 250 in an average Californian individual. Tsimane samples had previously been sequenced at lower resolution. The new analysis provided a deeper comparison, but its findings about two populations should not be treated as a complete account of human gut microbiomes worldwide.
“Our study establishes that the hundreds of bacterial species that are rare or missing in industrialized microbiomes were ancient companions of ours as we migrated around the globe, likely passed from generation to generation for millennia.”
— Justin Sonnenburg, Stanford University microbiology and immunology professor and senior author
Limits of the Migration Evidence
The researchers inferred the timing of microbial strain separations from genetic data; they did not recover these microbes from ancient human remains or directly track them through prehistoric journeys. The reported alignment with migration periods supports a possible connection, but does not establish the exact route or prove that every shared species traveled with human ancestors.
The source report does not provide the full methods, sample counts or detailed uncertainty ranges for the dating estimates. It is also unclear which specific environmental, dietary or social factors account for the lower presence of these species in industrialized populations. Most importantly, the study does not determine whether microbiome diversity loss contributes to chronic disease or whether restoring particular microbes would affect health.
Further Tests of Microbial History
The immediate next step is for researchers to test the proposed history across more populations and microbial datasets, and to examine how robust the strain-splitting estimates are under different methods. Comparisons with additional communities could help distinguish broadly shared human-associated lineages from microbes shaped by local diets and environments.
Follow-up research would also need to investigate health effects directly, rather than infer them from population comparisons. The report does not identify a specific next experiment, clinical trial or publication date. For now, the study offers evidence about shared species and their estimated evolutionary timelines, while the health consequences of their decline remain open questions.
Key Questions
Which populations did the study compare?
Researchers compared gut microbiomes from the Hadza in Tanzania and the Tsimane in Bolivia, using deep sequencing for the Tsimane samples and previously sequenced Hadza samples.
What did the researchers find?
The study reported 1,231 bacterial species shared between the sampled groups. Genetic analyses suggested that some microbial strains separated around periods associated with major prehistoric human migrations.
Does the study prove that industrialized lifestyles cause disease by reducing gut microbes?
No. The study found that many shared species are rare or absent in industrialized populations, but it did not establish that losing those microbes causes chronic disease.
Did researchers find microbes preserved from ancient humans?
No. They analyzed present-day stool samples and used microbial genetic data to estimate when strains separated. The study did not directly recover microbes from prehistoric people.
Source: rss
