Stable isotope analysis of bone collagen from 25 individuals buried at the Selivanovsky II burial ground (18th–16th centuries cal BC) indicates a diet dominated by terrestrial animal protein, with δ15N values ranging from 9.70‰ to 11.15‰ and δ13C values from –19.16‰ to –18.57‰, reflecting minimal reliance on aquatic resources or C4 plants and consistency with consumption of domesticated ruminants such as cattle and horses.

When people eat mostly meat and milk from cows and horses, the nitrogen and carbon atoms from those foods get locked into their bones as they grow. The type of food they eat changes the chemical signature of those atoms in predictable ways. Bones that grow slowly, like the thigh bone, keep a record of what they ate over many years, while bones that renew faster, like the rib, show what they ate more recently. This creates a clear pattern that matches eating mostly land animals and not fish or grains like corn.