Fig. 1: LOESS regression trends in the environmental conditions and biodiversity of herbivorous megafauna in eastern Africa.

Trends show temporal changes in the fraction of woody cover among megafaunal communities (a), as well as in megafaunal taxonomic (b), phylogenetic (c), and functional diversity (d). Each data point represents a 250,000-year time bin. Among the species of megafauna occurring in each time bin, taxonomic diversity is measured as species richness; phylogenetic diversity as the sum of the branch lengths (in millions of years) of the phylogenetic tree connecting genera; and functional diversity as the mean Euclidean distance between species’ trait values (body mass, hypsodonty, and loph count) and their centroid in three-dimensional space (see Supplementary Fig. 4). Each data point is presented as a mean value ± one standard error from n = 1000 independent samples of communities (a), species occurrences (b), genera (c), or species (d) (see Methods). LOESS regression curves use a smoothing parameter of 0.75. Faded gray bars denote breakpoints from breakpoint analysis. Blue-shaded areas refer to events related to environmental change and orange to events in hominin evolution. These events are encompassed in key time intervals, as follows: 7.5–5 Ma includes the onset of grassland expansion and the emergence of hominins (7 Ma); 3.3–3 Ma includes the mid-Pliocene Warm Period and the development of Oldowan hominin tools (3 Ma); 1.9–1.7 Ma includes the increase in climate variability and aridity, as well as the emergence of Homo erectus (1.9 Ma) and their development of Acheulean technology (1.7 Ma); and ≤1 Ma includes the intensification of periods of aridity, as well as rapid cranial growth in hominins (1 Ma). Circled points in a and c reference the most dramatic decline in phylogenetic diversity and the associated change in woody cover. Source data are provided as a Source Data file.