Period· The columns of time

Neogene

23 Ma → 2.6 Ma

In the Neogene, from 23 to 2.6 million years ago, grasslands spread across the continents, the Mediterranean dried out and refilled, and a lineage of African apes stood upright.

Period in which grasslands spread across the continents, the Mediterranean dries out and refills, and a lineage of African apes acquires bipedalism.

What the evidence shows

The cooling and drying of the climate alters vegetation. Tropical grasses adopt a different photosynthetic pathway, the C4 pathway, more efficient when carbon dioxide is scarce and the air hot and dry. Between eight and three million years ago these grasslands take over whole continents and replace woodland. Open landscape favours running animals, and the dentition of grazers changes with the nature of the fodder. Africa preserves the fossils bearing on the human lineage: a branch of apes separates there and acquires bipedalism, the evidence being distributed across both epochs, a distorted cranium from Chad in the Miocene and, in the Pliocene, footprints, stone tools and the oldest mandible attributed to Homo.

Bounds and conventions

Its limits are golden spikes. The expansion of C4 plants is dated by carbon isotopes, in fossil teeth, which record what animals ate, and in ancient soils, which record what grew above them; the dietary change is therefore better documented than the change in landscape, and the cause of the shift is not established. The hominin fossils are each contested, and their dating belongs to the epochs that carry them.