This is a Preprint and has not been peer reviewed. This is version 1 of this Preprint.
Dietary models of primate brain evolution omit the gut microbiome
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Authors
Francisco Chávez 
Abstract
DeCasien et al. reported that diet, rather than sociality, predicts relative brain size across primates, with frugivores having larger brains than folivores. Their interpretation moves the discussion from sociality towards ecology yet leaves the proposed energetic link biologically unspecified. The matter arising from this dietary framework is gut microbial metabolism, a plausible mechanistic link between dietary substrates and the energy and metabolites available to support neural development and maintenance. Microorganisms help determine how much energy and which metabolites a host obtains from a dietary substrate, while social contact helps transmit those microorganisms among hosts. Evidence for both processes was available when the article appeared. Because the study represented diet using broad feeding categories or percentage frugivory, it could not distinguish food intake from the nutrition realized by the host-microbe system. The results establish a dietary association, but they do not identify the mechanism through which diet could support the evolution of a larger brain.
DOI
https://doi.org/10.32942/X2J692
Subjects
Life Sciences
Keywords
Brain evolution, Primates, Ecology, Microbiome
Dates
Published: 2026-10-15 15:08
Last Updated: 2026-10-15 15:08
License
CC BY Attribution 4.0 International
Additional Metadata
Conflict of interest statement:
None
Language:
English
Metrics
Views: 36
Downloads: 2
Comment #356 Oliver L. Pescott @ 2026-10-15 19:15
Perhaps worth noting that most of this is AI-generated (76% according to Pangram, although the tone is pretty obvious to a regular LLM user). I don't this is necessarily a problem for the scientific argument, although it does beg the question of whether the named author should be getting full credit (and then there is the question of the human effort required to moderate these submissions on ecoEvoRxiv and, presumably, at the journal where they are published). Ultimately we need some sort of clearing house for papers and their comments that is managed by AI as well to stop this breaking the system. As I said though, I can see this ultimately as a net gain for science (assuming that we are interested in truth-seeking as well as career-making).