Gut microbes followed migrating humans across continents, new study

The Hadza people are traditional hunter-gatherers who have inhabited northern Tanzania for millennia, relying on foraging and hunting for survival. Meanwhile, the indigenous Tsimane people forage, fish, and hunt in the Bolivian Amazon, approximately 7,000 miles away. At first glance, these two rural communities appear to have little in common, separated by vast geographic distances and distinct environments.

However, a groundbreaking study published in the scientific journal Nature shows that they share remarkable similarities regarding the bacteria living in their guts. By analyzing stool samples from both groups, researchers discovered a shared microbial profile that sets them apart from urban populations living nearby. This microbial kinship implies that certain strains of bacteria have accompanied humans for a very long time, likely coevolving to mutual benefit.

Experts explain that these isolated communities maintain lifestyles much closer to those of our ancient ancestors. Because of this, their bodies remain hospitable to microbes that were handed down through countless generations of human evolution. Senior study author Justin Sonnenburg, a professor of microbiology and immunology at Stanford University, expressed surprise at the extent of the overlap.

According to Sonnenburg, if humans hosted specific microbes over vast periods of evolutionary history, our genomes may have adapted to expect those precise functions. Consequently, losing this microbial biodiversity in modern industrialized societies could pose significant challenges for human biology as it struggles to adjust to an altered internal ecosystem.

Not all researchers are ready to declare the ancestral microbiome universally superior, however. Andrew Moeller, an associate professor of evolutionary biology at Princeton University who was not involved in the research, points out alternative explanations for the differences observed. He suggests that the industrialized microbiome profile might actually represent a successful adaptation to a modern lifestyle rather than a detrimental loss.

Moeller notes that from a health perspective, it remains unclear whether the disappearance of ancestral microbial groups in urban populations is fundamentally good or deleterious. Documenting precisely what has been retained by rural groups and what has been lost in cities represents a crucial first step toward answering this complex evolutionary question.

As scientists continue to decode the intricate relationship between humans and their internal microorganisms, the findings underline the profound impact of modern living on our biology. Further research will be necessary to determine how specific bacterial strains influence long-term health and whether restoring lost microbial diversity could benefit populations in industrialized nations.