The Evolution & Medicine Review

What are the consequences of the disappearing human microbiota?
by Martin J. Blaser and Stanley Falkow
in Nature Reviews Microbiology   doi:10.1038/nrmicro2245

Who are we? From prions and organelles up through neighborhoods and nation-states, we are groups of groups of groups. In this thoughtful, provocative paper Blaser and Falkow remind us that 90% of our cells are non-human. Vertebrates coevolved with vast communities of microorganisms with whom they share complex endosymbiotic relationships. The authors assert that the human microbiome has been dramatically altered by changes in human ecology. They expand on their disappearing microbiota hypothesis, using the decreasing prevalence of Helicobacter pylori as an example, and argue that such alterations have physiologic and clinical consequences that must be better understood.

Mark D. Schwartz, MD
Associate Professor of Medicine
NYU School of Medicine

Humans and our ancestors have evolved since the most ancient times with a commensal microbiota. The conservation of indicator species in a niche-specific manner across all of the studied human population groups suggests that the microbiota confer conserved benefits on humans. Nevertheless, certain of these organisms have pathogenic properties and, through medical practices and lifestyle changes, their prevalence in human populations is changing, often to an extreme degree. In this Essay, we propose that the disappearance of these ancestral indigenous organisms, which are intimately involved in human physiology, is not entirely beneficial and has consequences that might include post-modern conditions such as obesity and asthma.