Nearly 50% of the world’s population lives in urban settings – with that number expected to increase dramatically over the next few decades. While this mass migration of humanity has greatly improved opportunities for many, mounting evidence suggest it comes at an ecological price for the inhabitants of these new concrete and steel villages of the modern world.

If you were to drop a Hadza hunter-gatherer from Tanzania at a street corner of one of these mega-cities, the endless stream of cars, noise and frenzied running about would no doubt cause some trepidation as he slowly stepped back from the street corner. I suspect it wouldn’t take long for our Hadza friend to think to himself, “what have these people done with all the plants and animals?” 

With real estate at a premium and a Starbucks needed on every street, there’s very little incentive to nurture nature anywhere outside of designated parks, limited green spaces or on our window seals. As mounting research and our work in Africa with the Hadza is starting to reveal, humanities steady march away from nature and its menagerie of plants, animals and microbes, may have given rise to one of the greatest, ongoing ecological disasters in human history: the modern human gut.

Advances in technology and computing power have lead to an astounding drop in the costs of genetic research. At the forefront of this new scientific and medical revolution has been the study of microbes – the tiny little bacteria, viruses and fungi that inhabit every imaginable piece of fleshy real estate – inside and out – of every living thing on earth. And that includes us.

What researchers are starting to discover is that these tiny little microbes might be playing a role in diseases as diverse as obesity, autoimmune disease, heart disease, IBD/IBS, cognitive disorders, atopy, some cancers, and so on. 

For the last few years, colleagues and I have been living and working with the Hadza hunter-gatherers of East Africa. Far from being untouched by the modern world, the Hadza still collect and hunt nearly the same plants and animals that humans have for millions of years. Importantly, as an active and intimate member of the landscape of East Africa, the Hadza are literally covered in the patina of nature and its diversity microbes, which has endowed the Hadza with one of the most diverse set of gut microbes of any group in the world. It’s not a stretch to say that the Hadza gut, and presumably that of our not-so-distant ancestors, sits at the crossroads of a microbial super highway that shaped our immunity and what made us human.

As mounting evidence has started to reveal, the ongoing assault against our microbial diversity in the modern world through our buildings that walls off the microbial world outside to the overuse of antibiotics to changing birthing methods and a decrease in breastfeeding to diet and hyper-hygiene, has “potentially” led to an increase in a dizzying number of modern ailments.

With the kind support of the A Team Foundation and others, we will continue to try to understand what the gut (and skin) microbiome of a free-living human population looks like as the Hadza literally run gut first into the buzz saw of globalization. The clock is ticking.

Our work is not focused – or even suggesting – that a Hadza diet is what we should be eating. What we are suggesting and discovering is that all humans on Earth may have depended on nature for a steady flow of microbes – that is, constant dispersal and immigration from a pool or sink of microbes maintained in nature. This intimate connection to the microbial super highway on the landscapes that gave rise to our genus, assured that humans had a steady supply of new microbes to bolster against any drop in diversity brought on by shifts in diet or other perturbations of life.

Remove that natural source of microbes – what we’ve essentially done in the modern world – then any assault on our gut microbiome such as antibiotics or diet could possibly be met with a shift in our inner ecosystem that may tilt one towards opening the microbial door to disease. If this is indeed the case, then human-microbe health is directly linked to ecosystems much larger than ourselves.