text: Plants can be characterised by the ratio of carbon isotopes they sequester, due to alterations in the evolution of photosynthetic biochemical pathways. So-called C3 plants fix CO into a 3-carbon molecule and have a greater proportion of C, whereas C4 plants fix it into a 4-carbon molecule, and have a carbon isotope signature with higher C. This signature translates across trophic levels and can be used to determine the diets of people and animals. Isotopic analysis has been used to illuminate the diets of the different species of the Paranthropus genus. It was determined that P. boisei had a reduced ratio of C3:C4, meaning they likely consumed a greater proportion of grasses and sedges than trees, shrubs and temperature grasses. P. aethiopicus showed a similar trend, whereas P. robustus was a generalist, with a broader dietary niche. Furthermore, carbon isotope analysis shows that around 2.37 million years ago, hominins displayed a widespread shift to favour C4 plants.