The diagram demonstrates differences between two skeletal structures of two human ancestors.
Overall, because AA had to climb frequently, their skeletons were larger in size than those of HE, especially hands and gluteus.
Looking at the upper part of the body, AA had an unbalanced head, compared to a balanced head of HE. While a wide chest and a short, and wide waist were witnessed in the AA’s skeletons, the HE ancestor had a narrow chest and a tall, and narrow waist. In order to climb easily, AA had high and narrow shoulders, long forearms and big hands, whereas HE developed low and wide shoulders, short forearms and small hands.
Regarding the lower part of two skeletons, AA ancestor had a long femoral and toes which were suitable for climbing trees, while HE had shorter ones. Additionally, a long achilles tendon was witnessed in the HE’s skeleton, whereas the contrast was seen in the figure for the skeleton of HA. Due to a large hip, knee, ankle joints and heel bone, the HE ancestor could run easier, while those of the AA’s skeleton were opposite in size. Finally, a stabilized foot arch of the HE’ skeleton supported it during the running period, and a partial foot arch which created the flexibility of the AA ancestor for walking and climbing activities.