Did gut microbes travel with us? A genomic model of deep migration
A new comparison of living Tsimane and Hadza communities traces long microbial lineages. The ancient journey is inferred, not observed directly.
A historical signal in living microbiomes
The people who migrated across continents carried more than their own genomes. A Nature paper published on 7 October 2026 asks whether some gut microorganisms also travelled with human lineages over deep time. The researchers compared metagenomic data from Tsimane adults in Bolivia with previously sequenced data from Hadza participants in Tanzania. They identified 1,231 microbial species shared across these cohorts. Population-genetic analyses of 636 shared species found divergence and gene-flow patterns consistent with long-term human–microbe co-migration. This is a model built from living communities, not a direct sequence of prehistoric samples. Nature ↗
What the team actually measured
The study deeply sequenced 133 faecal samples from 85 Tsimane adults and compared recovered microbial genomes with an existing dataset from 137 Hadza participants. It then examined variation within shared species to estimate how their populations diverged and exchanged genes. Some inferred split times approximately align with major phases of human movement out of Africa and into the Americas. Such alignment is meaningful evidence for a historical relationship, but it is not a timestamped record of a single migration or proof that every microbe followed exactly the same human route. Nature ↗
Why the result matters
Many gut species common in these non-industrialized communities are rare or absent in the industrialized populations included in the comparison. If some associations have endured across many generations, their present-day distribution cannot be explained only by recent diet or local environment. The paper therefore adds an evolutionary dimension to discussions of microbiome loss. It does not show that a particular missing species causes a particular disease, and it does not recommend introducing microbes as a treatment. Historical inference and clinical intervention have very different evidence thresholds. Nature ↗
The uncertainties inside the clock
Microbes evolve quickly, exchange genes and can move between people in ways that do not mirror human family trees. Population structure and limited sampling can distort estimates of when lineages separated. The authors use complementary analyses and discuss these constraints, but their ancient history remains inferred from contemporary genomes. Ancient faecal samples have supplied valuable clues elsewhere, yet preservation and time coverage are uneven. The most defensible conclusion is that many shared species show patterns compatible with very long association, while exact routes and health consequences remain open. Nature ↗
People are not a comparison category
The Tsimane and Hadza are living communities, not proxies for prehistoric humans. The paper reports consent and research collaboration with Tsimane governing and community bodies, a context that belongs in any responsible account of the data. Its findings should not be used to rank populations as more or less evolved. The useful question is how lifestyle, environment, ancestry and microbial exchange jointly shape today's communities—and how to study that history without turning contemporary participants into an imagined snapshot of the distant past. Nature ↗