The evolution of hominoid locomotor versatility: Evidence from Moroto, a 21 Ma site in Uganda

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, multiple paleoenvironmental proxies were analyzed in conjunction with hominoid fossils from the Moroto II site, Uganda. The data indicate seasonally dry woodlands with the earliest evidence of abundant C4 grasses in Africa based on a confirmed age of 21 Ma. We demonstrate that the leafeating hominoid Morotopithecus consumed water-stressed vegetation, while 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