Why Hunter-Gatherers Had 50% More Gut Bacteria Than We Do

There is a photograph that circulates in gut health research circles: a Hadza forager in northern Tanzania, walking back to camp with a day’s foraged harvest of tubers, berries, and baobab fruit. It looks, on the surface, like any account of a subsistence diet. What it actually represents, according to over a decade of metagenomic sequencing, is one of the last living windows into the gut microbiome our species carried for 95% of its evolutionary history — and it looks nothing like what most of us are carrying now.

The Hadza are one of the last populations on Earth still living a substantially hunting-and-gathering lifestyle, foraging tubers, berries, honey, and wild game around Lake Eyasi in the Rift Valley. Because their diet remains largely unprocessed and seasonally wild, their gut microbiome has become one of the most valuable natural experiments in human microbiology — a living comparison point for what industrialisation has done to the bacteria living inside us.

Do hunter-gatherers really have more gut bacteria than we do? Yes. Multiple studies confirm the Hadza carry significantly higher gut microbial richness and biodiversity than urban Italian, European, and North American populations, along with entire bacterial genera — including Treponema — that are essentially absent from Western guts. The difference is attributed primarily to dietary fibre diversity, not genetics.

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The landmark study: what Schnorr and colleagues found

The foundational research here is a 2014 study published in Nature Communications (Schnorr et al.), which sequenced the gut microbiota of 27 Hadza hunter-gatherers and compared it against Italian urban controls and other African farming populations. PMC3996546

The findings were striking on several fronts. The Hadza showed significantly higher levels of microbial richness and biodiversity than the Italian urban comparison group. Their gut communities were enriched in Prevotella, Treponema, and unclassified Bacteroidetes — genera associated with the ability to break down complex, fibrous plant polysaccharides that the human gut alone cannot digest. Perhaps most tellingly, Bifidobacterium — one of the bacterial genera most commonly promoted in Western probiotic supplements and yoghurt marketing — was essentially absent from Hadza guts entirely.

This last point is worth sitting with. Bifidobacterium is not simply “good bacteria” in some universal sense; its abundance in Western guts is a marker of a particular dietary pattern — one rich in dairy and refined prebiotic fibres, and comparatively low in the diverse, tough plant fibres that dominate a forager’s diet. The Hadza’s gut ecosystem is not “deficient” in Bifidobacterium. It is simply organised around a completely different fuel source. Evidence level: human metagenomic sequencing study, cross-sectional comparison.

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Treponema: the bacteria that vanished with industrialisation

Of all the differences documented, the loss of Treponema from Western guts is one of the most consistently replicated findings in comparative microbiome research. A follow-up study examining traditional rural populations found that Treponema succinifaciens specifically enriches the gut microbiota of populations still living traditional, high-fibre lifestyles — and is reliably absent from industrialised populations. PMC6276622

Treponema species are specialists in breaking down resistant plant fibres — the tough, complex polysaccharides found in wild tubers, fibrous roots, and unprocessed wild greens that never make it into a modern refined diet. A broader review of post-weaning gut metagenomes across dozens of populations confirmed the same pattern globally: industrialised Western populations reliably show a loss of Treponema, alongside a corresponding rise in Bifidobacterium and other genera associated with processed, low-fibre diets. PMC4940381

The honest evidence position: no controlled human trial has restored Treponema to a Western gut through diet alone, and it may be that transmission of these species between people — not just diet — is required for their re-establishment. Researchers studying the topic have suggested that reduced person-to-person and generational transmission, driven by sanitation, smaller households, and reduced environmental microbial exposure, plays a role alongside diet. This is an area of active, unresolved research. Evidence level: cross-population comparative studies; mechanism plausible but not experimentally proven in humans.

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The diet driving the difference: what Hadza foragers actually eat

The Hadza diet varies by season but consistently includes an extraordinary range of plant species compared with a typical Western diet. Foraged tubers (several wild Vigna and other root species), baobab fruit and pulp, wild berries, honey, and baobab seeds form the plant backbone, while meat and honey provide the remainder of caloric intake depending on season.

The critical detail for gut health is not any single food but the sheer number of different plant species involved. Estimates of Hadza dietary plant diversity run into the hundreds of species consumed across a year — compared with typical Western diets, in which a small number of studies estimate most adults eat well under 30 unique plant species in total, often far fewer. Since different fibre types feed different bacterial species, a gut that only ever receives fibre from wheat, potato, and a handful of supermarket vegetables can only ever support a fraction of the bacterial diversity that a genuinely varied wild diet supports.

A landmark study published in Science in 2017 (Smits et al.) tracked the Hadza gut microbiome across a full year and found that it shifts dramatically and reproducibly with the seasons — expanding during the dry season when fibrous tubers dominate the diet, and contracting during the wet season berry glut. PMC5891123 This seasonal cycling itself may be significant: a gut microbiome that expands and contracts in response to changing plant fibre inputs throughout the year may be inherently more resilient and adaptable than one locked into a static, low-diversity Western diet all year round.

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What this means for a UK forager’s plate

None of us are about to move to the Rift Valley and adopt a Hadza diet, nor should we try — the research does not suggest that industrialised populations should attempt to literally replicate a hunter-gatherer diet. What it does suggest, robustly, is a mechanism: fibre diversity from a wide range of plant species is the single most reliable lever available to support a more diverse gut microbiome, and foraging is one of the most practical ways to genuinely expand that diversity.

Wild plants offer fibre types that cultivated vegetables generally do not. Wild nettle, dandelion, burdock, and yarrow contain complex, less-processed fibre structures and defensive plant compounds that cultivated, selectively bred vegetables have often had bred out of them in favour of palatability. We covered the prebiotic mechanisms in bitter wild plants in detail in our post on the prebiotic power of bitter wild plants, and burdock’s specific inulin content in our burdock deep-dive.

A practical target: nutrition researchers studying microbiome diversity, including the team behind the American Gut Project, have suggested that eating 30 or more different plant species per week is associated with meaningfully greater gut bacterial diversity than eating fewer than 10 — a far more achievable target than 30 sounds once herbs, spices, wild greens, and varied vegetables are all counted individually. A weekly foraging walk that adds nettle, dandelion, wild garlic in season, or hedgerow fruit to your usual vegetables is a genuine, practical way to move that number upward.

Reduce reliance on refined, low-fibre staples. The consistent finding across the Hadza literature and the broader Westernisation studies is that refined carbohydrates and low-fibre processed foods correlate with the specific loss of fibre-digesting bacterial genera. This does not mean eliminating any food group; it means treating whole, fibrous, varied plant foods as the daily default rather than the occasional extra.

For the fuller picture of how our ancestral diet shaped the gut microbiome we carry today, see our pillar post on The Wild Gut: how our ancestral diet of foraged plants shaped your microbiome.

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Safety and identification note

This post discusses gut microbiome research rather than naming a specific UK wild plant to identify and harvest. If you are new to foraging nettle, dandelion, burdock, or yarrow to add fibre diversity to your diet, see our dedicated plant guides linked above, each of which includes full identification, lookalike, and safety guidance specific to that species.

Never eat any wild plant unless you are 100% confident in your identification. If in doubt, leave it out.

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Join a foraging workshop

Building genuine plant diversity into your diet starts with knowing what is safe to forage and how to identify it with confidence. Chloe’s foraging workshops cover exactly the wild plants discussed here — you’ll walk, identify, taste, and leave knowing precisely what you’re looking at. Find out more →

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This content is for educational purposes only and does not constitute medical advice. Wild plants can be dangerous if misidentified. Never consume any wild plant unless you are completely confident in your identification. Some wild plants can interact with medications. Always consult your GP before using wild plants medicinally, particularly if you are pregnant, breastfeeding, or taking medication.