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Could the Gut’s Nervous System Have Evolved Before the Brain?
The hypothesis is that the enteric nervous system may have evolved before the brain, which later developed to help meet the gut’s needs. The gut’s neural circuits can coordinate digestive movement, but evidence of that present day function does not establish which nervous system evolved first.
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Key takeaways
- The hypothesis is that the enteric nervous system may have evolved before the brain, which later developed to help meet the gut’s needs.
- The gut’s neural circuits can coordinate digestive movement, but evidence of that present day function does not establish which nervous system evolved first.
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openai.comCreate a landscape editorial hero image for this Studio Global article: What is the hypothesis proposed by Flinders University researchers Tim Hibberd, Hayley Rhodes and Nick J. Spencer in their opinion piece “Th. Article summary: The hypothesis is that the enteric nervous system (ENS)—usually called the gut’s “second brain”—may instead be the evolutionarily first brain, with the head brain developing later to help meet the gut’s energy-acquisitio. Topic tags: general, education, academic, general web, government. Style: premium digital editorial illustration, source-backed research mood, clean composition, high detail, modern web publication hero. Use reference image context only for broad subject, composition, and topical grounding; do not copy the exact image. Avoid: logos, brand marks, copyrighted characters, real person likenesses, fake screenshots, UI text, readable text, watermark
Flinders University researchers Tim Hibberd, Hayley Rhodes and Nick J. Spencer propose that the enteric nervous system (ENS)—the network of nerves in the gut—may have preceded the brain in evolution. In this “gut-first” view, the brain developed later, initially helping organisms meet the gut’s demands for acquiring energy. The authors present this as an interpretation of physiological and evolutionary evidence, not as a sequence directly demonstrated by a new experiment. 1
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Why the gut-first hypothesis is plausible
The ENS is more than a passive receiver of commands from the brain. It contains intrinsic neural circuits that help regulate intestinal muscle contraction and relaxation, giving the gut a degree of local control over movement. 43
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Research by Spencer and colleagues has also linked synchronized activity in enteric circuits to propulsion along the large intestine in mice. That work shows how the ENS can coordinate complex digestive movement; it does not, by itself, reveal when the ENS or the brain first evolved. 42
Other studies describe pathways connecting enteric activity with the wider nervous system. Research has examined ENS-mediated sympathetic reflexes and sensory nerve endings linking structures in the colon with the colon–brain axis. These findings provide examples of communication between gut circuits and other parts of the nervous system, rather than evidence that the gut operates in complete isolation. 44
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Together, these physiological findings make it reasonable to ask whether nervous-system evolution might be reconsidered from the gut’s perspective. The researchers’ central evolutionary suggestion, as summarized by Flinders University, is that the brain may have evolved later to support the gut’s needs. 1
What the evidence does not prove
The key distinction is between what the ENS can do now and what evolved first. Local control of gut movement supports the idea that enteric circuits are functionally important. It does not establish that they appeared before the brain, or that energy acquisition was the original reason a brain evolved.
The report describes the paper as an opinion piece drawing on physiology and evolutionary biology, rather than a report of a new experiment. Its contribution is therefore the proposed interpretation of existing evidence—not direct observation of nervous-system origins. 39
The specific estimate of 200–600 million neurons and the claim that removed bowel segments can produce complex movements are not confirmed in the available source excerpts, so they should not be treated here as verified support for the evolutionary timeline. More broadly, present-day physiology alone cannot reconstruct a unique sequence of events from deep evolutionary history.
What the reframing could mean for future research
A gut-first perspective could encourage researchers to test how enteric circuits contribute to energy handling and to conditions involving digestion or metabolism. It might also prompt further study of gut–brain interactions in diseases such as Parkinson’s. These are possible research directions, not findings that the hypothesis explains those conditions or establishes where they begin.
The proposal does not, on its own, justify a change in medical treatment. Its immediate significance is conceptual: it asks whether the gut’s nervous system should be considered central to explanations of nervous-system evolution, rather than treated only as a “second brain.”
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What is the short answer to "Could the Gut’s Nervous System Have Evolved Before the Brain?"?
The hypothesis is that the enteric nervous system may have evolved before the brain, which later developed to help meet the gut’s needs.
What are the key points to validate first?
The hypothesis is that the enteric nervous system may have evolved before the brain, which later developed to help meet the gut’s needs. The gut’s neural circuits can coordinate digestive movement, but evidence of that present day function does not establish which nervous system evolved first.