Faecal analysis has added grist to the debate over whether dietary silica contributed to the evolution of herbivores' high-crowned teeth. The compound, which is found in dust and in certain plants, such as grasses, is harder than tooth enamel and can wear teeth down.
Jürgen Hummel at the University of Bonn in Germany and his colleagues measured the levels of silica, which is not absorbed or degraded during digestion, in the faeces of 15 species of African herbivore, including giraffes, antelopes and zebras. They used this as a proxy for the amount of silica ingested, and found that herbivores with higher-crowned teeth tend to have higher levels of silica in their diet. This supports the argument that herbivores evolved these teeth to offset the dental erosion caused by their diet.