The science behind the idea of restoring the intestinal microbiome to an ancestral state is shaky, skeptics say, and in some cases unethical.

Country Microbes and City Microbes

Despite the enthusiasm for rewilding, there is no good evidence yet that adding microbes to the guts of people in industrialized societies will improve health. Correlations between nonindustrialized societies’ microbiomes and an apparent protection from diseases like diabetes do not mean that changing the microbiomes of people in industrialized societies will give them the same protection.
Keolu Fox, an anthropologist and genomics researcher at the University of California, San Diego, calls the idea that such microbes will offer protection “Just So Stories,” after the tales by Rudyard Kipling. It is easy to build a narrative based on correlations, he said.

Researchers have a challenge ahead connecting the microbes and these diseases, Dr. Gordon said.

“A lot more needs to be done to figure out what these organisms actually do and whether they do the same things in different microbial contexts,” he said.

For Katie Pollard, director of the Gladstone Institute of Data Science and Biotechnology in San Francisco, finding cures for autoimmune diseases is not just an academic exercise. She has two chronic inflammatory conditions, ulcerative colitis and ankylosing spondylitis, and her son has Crohn’s disease.

“I would love for my son to get better. And myself,” she said.

And while she agrees that “the microbiome plays a role in these illnesses,” she questions the strategy.

“Even if a modern Hadza person wanted to donate, how could this be the solution when microbiomes change on a day-to-day basis based on what goes into our bodies?” She added that “It’s a huge leap to say, ‘Let’s go back to a microbiome found in a nonindustrialized population.’”

Dr. David Relman, professor of medicine, microbiology and immunology at Stanford, had similar concerns.

“We have a certain ‘grass is greener’ attitude. We wish for the olden days when life was simpler and we hadn’t messed with the world the way we have today.” But in the olden days, he added, “life expectancy was much, much shorter and people died of infections before they ever could get cancer.”
Keolu Fox, an anthropologist and genomics researcher at the University of California, San Diego, calls the idea that such microbes will offer protection “Just So Stories,” after the tales by Rudyard Kipling. It is easy to build a narrative based on correlations, he said.

Researchers have a challenge ahead connecting the microbes and these diseases, Dr. Gordon said.

“A lot more needs to be done to figure out what these organisms actually do and whether they do the same things in different microbial contexts,” he said.

For Katie Pollard, director of the Gladstone Institute of Data Science and Biotechnology in San Francisco, finding cures for autoimmune diseases is not just an academic exercise. She has two chronic inflammatory conditions, ulcerative colitis and ankylosing spondylitis, and her son has Crohn’s disease.

“I would love for my son to get better. And myself,” she said.

And while she agrees that “the microbiome plays a role in these illnesses,” she questions the strategy.

“Even if a modern Hadza person wanted to donate, how could this be the solution when microbiomes change on a day-to-day basis based on what goes into our bodies?” She added that “It’s a huge leap to say, ‘Let’s go back to a microbiome found in a nonindustrialized population.’”

Dr. David Relman, professor of medicine, microbiology and immunology at Stanford, had similar concerns.

“We have a certain ‘grass is greener’ attitude. We wish for the olden days when life was simpler and we hadn’t messed with the world the way we have today.” But in the olden days, he added, “life expectancy was much, much shorter and people died of infections before they ever could get cancer.”
He recalls a debate he had on rewilding at a conference a few years ago in New York with Dr. Blaser when he spoke about saving the microbiomes of the Hadza.

“I said, ‘if I have to live in New York City, I don’t want the microbiome of the Hadza,’” Dr. Relman said. The environment in New York is much different than in rural Tanzania, he noted, adding, “I am pretty sure my microbiome has figured out how to manage it.”

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