In Western Tanzania tribes of wandering foragers called Hadza eat a diet of roots, berries, and game. According to a new study, their guts are home to a microbial community unlike anything that’s been seen before in a modern human population — providing, perhaps, a snapshot of what the human gut microbiome looked like before our ancestors figured out how to farm about 12,000 years ago.
“There have been relatively few studies of gut microbiota among humans eating pre-industrial diets, relative to humans eating post-industrial ones,” said Lawrence David, a microbiologist from Duke University, who was not a part of the study. The new study, published today in Nature Communications, is timely and important, David says, because it provides a snapshot of pre-industrial human’s gut microbiota. It also indicates that the ecosystem in our guts adapts not only to our diets but to the environments we live in.
Researchers have known for decades that the biota in our gut vary depending on what we eat. But the Hadza microbiome still turned out to be surprisingly different.
To study the difference between the ancient and modern gut, researchers analyzed stool samples from 16 Italian urbanites and 27 Hadza foragers, of both genders.
The Italians’ gut flora was generally what they expected in Western diets, with some Mediterranean influences. The Hadza’s poop, however, was like stepping into a lost continent of microbe biodiversity. “The Hadza gut mibrobiome has an entirely unique combination of bacteria from any western population, or rural African population, that’s been sampled,” said co-author Alyssa Crittenden, a nutritional anthropologist from the University of Nevada, Las Vegas.
Many of the bacteria are species that the researchers had never seen before. And even familiar microbes were present in unusual levels in the Hadza belly. “The Hadza not only lack the ‘healthy bacteria,’ and they don’t suffer from the diseases we suffer from, but they also have high levels of bacteria that are associated with disease,” Crittenden said.
In westerners, Bifidumbacterium is a microbe that many nutrition scientists thought was essential to good gut health, but it is almost completely absent in the foragers. Likewise, high counts of the bacteria Treponema have been linked to maladies like Crohn’s disease and irritable bowel syndrome. Neither of these diseases exist among the Hadza, but their guts contain abundant Treponema.
Modern humans have only spent 5 percent of our history as farmers. Before that, most of our species were foragers of some type or other. “Studies like this one are rare opportunities for generating hypotheses about the bacteria that are most sensitive to diet and metabolism in the gut,” said David. The Hadza’s stomachs represent a reference ecosystem for comparing our modern lifestyles.