Bayesian dietary modeling of isotopic data from Yuzhniy Oleniy Ostrov estimates that 55% of total dietary intake came from terrestrial plants, which contradicts ethnographic records indicating that boreal hunter-gatherers consumed ≤25% plant foods, and this estimate may be inflated due to model assumptions of low lipid intake and high protein thresholds.

When a person eats mostly protein with very little fat, the body breaks down extra protein for energy instead of using fat. This causes the body to flush out more nitrogen waste, leaving behind heavier nitrogen atoms in the bones. At the same time, the carbon in the bones comes mostly from the protein sources, not from fats or plants, making it look like more plants were eaten than actually were. The amino acids in the bones match those of fish, proving the protein came from aquatic animals, not plants.