You are what you eat:
Using isotopes to work out the diet of extinct animals

C3 and C4 plants fractionate carbon isotopes in distinctly different ways and it is this feature which makes them suitable for palaeoenvironmental analysis.

By studying the carbon isotopes in animal/human bones or teeth the diet of the living animal can be extrapolated from the carbon 13 to carbon 12 ratio. The scientific way of writing this is 13C /12C. The 13C /12C ratio of fossil bones or teeth thus reflect the diet of an animal or human. If a sample has a relatively high ratio of 13C /12C, it means the animal ate a diet rich in C4 plants. If the animal is a carnivore it would indicate that they ate animals which were in turn eating the C4 plants.

African savannas have both C3 (trees and herbs) and C4 plants (tropical grasses), while forests have only C3 plants. Fynbos plants are generally C3. (See 'Plant photosynthesis and the palaeoenvironment').