Lost Microbes: How Your Ancestral Microbiome Could Fix Modern Digestive Disease

Our ancestry affects our microbiome.

Your ancestral microbiome was a treasure trove of diversity that puts today’s gut bacteria to shame. Scientists analyzing 2000-year-old human feces have discovered that our ancestors carried gut microbes we’ve completely lost – and these missing bacteria might explain why modern digestive diseases are skyrocketing.

Understanding our ancestral microbiome has become crucial for tackling today’s chronic disease epidemic. Research shows that loss of diversity in the gut microbiome directly connects to modern health problems (1), inspiring scientists to investigate what our ancestral microbiome actually looked like. By studying ancient gut bacteria preserved for millennia, researchers hope to unlock secrets that could help restore our compromised digestive health and combat diseases like obesity, diabetes, and inflammatory bowel conditions.

What Scientists Discovered About Our Ancestral Microbiome

To date, we don’t know much about what our gut microbiomes used to look like. Researchers wanted to find out. They believe it might help us better understand why modern microbiomes are more prone to disease such as obesity and diabetes.
 
In this study, researchers performed large-scale analyses of ancestral microbial genomes. The samples were up to 2000 years old, and taken from rock shelters in USA and Mexico.
 
The team analysed 8 fossilised human faecal samples – known as coprolites.
 
Coprolites can be valuable sources of information. They can tell us how we used to live, including insights on our ancestral diet and disease prevalence. 

The scientists found microbes that were completely absent from the gut microbiome today.

These samples contain certain gut microbes. So anyone with proper tools can compile a snapshot of the microbiome. That’s exactly what microbiologists decided to do!
 
The scientists first validated the coprolites using dietary and radiocarbon analyses. Afterwards, they extracted preserved DNA to identify the microbes.
 
They able to reconstruct 498 microbial genomes – 181 of which appear to originate in the human gut, rather than the soil.
 
The scientists found microbes that were completely absent from the gut microbiome today.
 
In total, 158 of these sequences seem to represent a distinct microbial species.

How Ancient Gut Bacteria Differ from Modern Microbiomes

The results were remarkable. The team discovered species never been seen in the modern microbiome. Out of 158 genomes, 61 were completely unknown to science – almost 40 percent!

Out of 158 genomes, 61 were completely unknown to science – almost 40 percent!

Overall, the ancestral guts more similar to non-industrialized microbiomes, and had:

  • Lower abundance of antibiotic-resistance genes
  • Fewer genes that make proteins to degrade glycans (sugar molecules found in mucus.) Mucus degradation in the colon is associated with diseases such as Crohn’s disease, Celiac disease and Ulcerative Colitis.
  • Higher numbers of transposases – enzymes that can cut, paste and replicate elements of DNA, which help with adaptation.

Mucus degradation in the colon is associated with diseases such as Crohn’s disease, Celiac disease and Ulcerative Colitis.

Ultimately, it appears the ancestral microbes were adapting to environmental shifts that were much more frequent than today. More transposases would therefore be necessary.

Why Ancestral Microbiome Diversity Matters for Modern Health

The culprit behind our microbiome’s decline? Our modern diet has become dangerously boring.

“In ancient cultures, the foods you’re eating are very diverse and can support a more eclectic collection of microbes,” explains microbiologist Alexsandar Kostic of the Joslin Diabetes Center. “But as you move toward industrialization and more of a grocery-store diet, you lose a lot of nutrients that help to support a more diverse microbiome.”

Think about it: our ancestors foraged dozens of wild plants, seasonal fruits, and varied protein sources. Today? Most of us cycle through the same 10-15 foods week after week, creating a microbial monoculture in our guts.

While researchers are still unraveling exactly how our simplified microbiome affects our health, this groundbreaking study proves that our ancestral guts hold powerful clues for healing modern bodies. The research team believes we’re just scratching the surface of what ancient feces can teach us.

“Similar future studies tapping into the richness of paleofeces will not only expand our knowledge of the human microbiome, but may also lead to the development of approaches to restore present-day gut microbiomes to their ancestral state,” the researchers conclude.

The future of gut health might literally be buried in the past.

References

  1. Blaser MJ. The theory of disappearing microbiota and the epidemics of chronic diseases. Nat Rev Immunol. 2017;17(8):461-463.

  2. Wibowo MC, Yang Z, Borry M, et al. Reconstruction of ancient microbial genomes from the human gut. Nature. 2021;594(7862):199-204.