Reassessing the Larval Consumption Hypothesis in Neanderthal Diet: A Quantitative and Multi-Proxy Evaluation

Persistent enrichment of Neanderthal collagen δ¹⁵N relative to local herbivore baselines has long stimulated debate regarding Neanderthal trophic ecology. A recent proposal suggests that the consumption of fly larvae from decomposing carcasses may have contributed to this enrichment. Here, this hypothesis is evaluated using a quantitative isotopic mixing model that integrates Middle Paleolithic herbivore baselines, published larval δ¹⁵N data, and multiple trophic enrichment factors. Across the modeled scenarios, larvae would need to supply substantial fractions of total dietary protein to achieve the absolute target of 14‰ observed in Neanderthal collagen. Because the modeled herbivore baselines range from 4‰ to 8‰, reaching this absolute target mathematically requires spanning an isotopic gap of +6‰ to +10‰. Consequently, the required larval contributions frequently exceed 40%, and in many baseline scenarios, exceed 100% of total protein intake. Sensitivity analyzes further show that plausible variation in herbivore baselines, larval δ¹⁵N values, or trophic enrichment factors does not modify this outcome. These results indicate that larval intake cannot independently account for Neanderthal nitrogen isotope enrichment and, at most, would represent a minor and isotopically negligible component of dietary protein. The consistent trophic enrichment of Neanderthal collagen relative to associated herbivore baselines is therefore more parsimoniously explained by high-trophic-level terrestrial carnivory, potentially amplified by environmental and ecological baseline variation.