Reconstructed setting· The columns of time

Cenozoic world

66 Ma → Today

This backdrop shows the Cenozoic: a closed forest that opens into grassland two thirds of the way through the era, with scattered trees left in the grass.

Backdrop representing a closed forest that opens into grassland two thirds of the way through the era, scattered trees remaining in the grass.

What the evidence shows

Grassland ecosystems were constituted in stages and not all at once: open-habitat grasses appear only in the Palaeogene, and the environments they dominate spread later, hence a closed forest in the earlier half of the composition. Open grassland is depicted from the Neogene, that is, from 23 million years, following the documented expansion of grass-dominated environments. Trees remain scattered rather than disappearing, the expansion of grasses having altered the proportions of the cover and not removed woody plants: what is depicted is wooded savannah, and that is what the data establish.

Bounds and conventions

A single composition represents the 66 million years across which the modern world is constituted. The transition depicted is real and dated, but it occurred at different dates on different continents, so that the backdrop presents a single calendar where there were several.