Living hominoids are distinguished by upright torsos and versatile locomotion. It is hypothesized that these features evolved for feeding on fruit from terminal branches in forests. To investigate the evolutionary context of hominoid adaptive origins, we analyzed multiple paleoenvironmental proxies in conjunction with hominoid fossils from the Moroto II site in Uganda. The data indicate seasonally dry woodlands with the earliest evidence of abundant C 4 grasses in Africa based on a confirmed age of 21 million years ago (Ma). We demonstrate that the leaf-eating hominoid Morotopithecus consumed water-stressed vegetation, and postcrania from the site indicate ape-like locomotor adaptations. These findings suggest that the origin of hominoid locomotor versatility is associated with foraging on leaves in heterogeneous, open woodlands rather than forests.

Proconsul is considered the best‐known fossil ape from the early Miocene (ca. 23.0–16.0 million years ago (Ma)), documenting an early period of evolutionary diversification prior to the origin of modern lineages. Fossils attributed to this genus include nearly every element of the skeleton, demonstrating that this ape—unlike its modern successors—had pronograde posture and practiced above‐branch locomotion. However, certain features of its arms and legs suggest more modern ape‐like adaptations, as do its larger brain and slower dental development. Broadly conceived, Proconsul comprises six species. This taxonomic diversity has led some to divide its species into new genera. Ugandapithecus was established for the largest species, Proconsul major , and subsequently populated with new species defined by novel combinations of early Miocene Proconsul specimens as well as one middle Miocene species. Alternatively, the genus Ekembo was created for the two more derived species from Rusinga and Mfangano Islands, while keeping the other four species within Proconsul .