Final answer:
The skeletons of Ardi and Lucy demonstrate the coexistence of bipedalism and physical traits associated with arboreal environments.
Step-by-step explanation:
The skeletons of Ardi and Lucy provide evidence for the coexistence of bipedalism and physical traits associated with arboreal environments. Ardi, an Ardipithecus, is believed to have lived in woodlands and had adaptations for both bipedalism and arboreal locomotion. Ardi had a grasping big toe for gripping branches and a mobile shoulder joint for climbing. Lucy, an Australopithecus afarensis, also had some arboreal adaptations, such as long arms and curved fingers. However, Lucy's pelvis and knee joints are indicative of bipedal walking.