The given diagram demonstrates the skeletal structure of two human ancestors: Australopithecus afarensis and Homo erectus.
Overall, the climber and the runner have notable distinctions, with the former generally having larger body parts, while the latter’s proportions are more balanced.
Regarding the head, Australopithecus afarensis displays a longer snout, whereas a more balanced head, and lower and wider shoulders are portrayed on Homo erectus.
In the upper part of these skeletons, the climber has a wider chest, while the runner features a shorter and narrower waist with a larger gluteus maximus, which is not shown. However, a shorter forearm and femoral neck are found on Homo erectus but not in the climber.
As for the lower part, most body parts of the runner’s skeleton (on the right) are larger or longer compared to those of the climber (on the left). The runner has larger hip, knee, and ankle joints with a longer Achilles tendon. In contrast, the climber possesses a smaller heel bone, longer toes, and a partial foot arch.