The given diagram shows the skeletal systems of two ancestors of humanity, namely Australopothecus afarensis and Homo erectus.
Overall, it is clear that most of the bone structure of the former ancestor is rougher and bigger, except for arms. The latter skeletal system also seems to be more familiar with modern people.
Concerning the upper parts, where there was an unbalanced head and longer snout as compared to Homo erectus. Moreover, the high and narrow shoulders with special arm bones’ features also contributed to the former’s climbing ability. With the short but wide waist, long forearm and small gluteus maximus, plus a wide chest, Australopithecus afarensis had shown the better tree climbing state, where Homo erectus illustrated the contrast.
In terms of the lower parts of the skeletal structures, the short femoral neck with larger hip, knee and ankle joints figured out the flexibility of the Homo erectus legs, where the Australopithecus afarensis set in opposition. Additionally, the short toes and stabilized foot arch allows the latter to hunt their prey persistently.