A recent study published in the journal Nature reveals that the Hadza hunter-gatherers of Tanzania and the indigenous Tsimane people of the Bolivian Amazon share remarkable similarities in their gut bacteria, despite being separated by thousands of miles. Researchers analyzed stool samples from both groups and found they shared around 1,200 of the same bacterial species, resulting in a near-90 percent overlap. This microbial kinship suggests that certain strains of gut bacteria have coexisted with humans for millennia, potentially dating back to common ancestors in Africa before human migration split the groups apart. The researchers used dating techniques based on bacterial mutation rates to determine that the microbial strains likely shared a common ancestor about 17,000 years ago, corresponding to the period before a land bridge connecting Russia and Alaska disappeared. The findings indicate that these populations pass ancestral microbes down through generations via human-to-human transmission rather than simply acquiring them from their immediate environment. Furthermore, the study showed that both the Hadza and Tsimane microbiomes differ markedly from those of people living in industrialized societies, with about 60 percent of their shared gut microbes being rare or absent in city dwellers. Justin Sonnenburg, a professor of microbiology and immunology at Stanford University and the study’s senior author, notes that losing this biodiversity may pose challenges for human biology, which has evolved to expect a specific set of microbial functions. However, other researchers like Andrew Moeller, an associate professor of evolutionary biology at Princeton University, caution that it remains unproven whether the industrialized microbiome profile is actually deleterious or simply adapted to a modern lifestyle. While determining the exact health impacts of losing these ancestral microbes requires further study, researchers agree that documenting what has been kept and lost is a vital step toward understanding human-microbiome co-evolution.
Source: npr.org
