The trophic position of ancient humans and animals can be reconstructed from bone collagen amino acid isotopes, with Neanderthals exhibiting trophic levels of 2.7–2.9 and early Homo sapiens exhibiting trophic levels of 2.2–2.6, indicating a greater reliance on animal protein by Neanderthals.

When animals eat food, their bodies break down proteins and reuse the amino acids. During this process, nitrogen atoms in certain amino acids lose a lighter form and keep a heavier form, making the remaining nitrogen heavier. This heavier nitrogen builds up more in animals that eat other animals, because each step of eating passes along more of this heavy nitrogen. The amino acids in bones that come directly from the original food sources keep their original nitrogen signature, while those that get recycled through metabolism become heavier. Scientists measure this difference to figure out how high up the food chain an animal ate.