The chart below shows the skeletal systems of 2 ancestors,one of them being Australopithecus afarensis, and the other being Homo erectus.
Overall, there is a significant disparity in the upper part of the skeleton between the two ancestors.In contrast, the lower part of the body shows fewer visible changes, although these differences remain essential.
It is readily apparent ,that Australopithecus afarensis-walker and tree climber , has a less balanced head than Homo erectus-walker and endurance runner. Additionally, it is noticeable that tree climbers and runners have wide and narrow chests , high and low oriented shoulders respectively. Climbers tend to have longer forearms than the Homo erectus, additionally the reason behind it might be in the fact that climbers are more likely to spend more time on the trees, while the latter primarily spends most of its lifespan on the ground. Over time,short waist evolved into a tall one, making the waist narrower.Moving further down the skeleton, following the pattern, the gluteus maximus became bigger in theHomo erectus.
As for the lower part of the body, the femoral neck became shorter in theHomo erectus, while hip, knee and ankle joints became larger. Homo erectus has longer Achilles tendon than Australopithecus afarensis, with this phenomenon being explained by the greater need for endurance legs for more long-term runs. One of the most notable differences can be seen in the toes, with the earlier ancestor having partial toes, and the modern one having fully developed toes. The foot arch in the modern specimen is more stabilised-compared to the earlier one, with the heel bone being relatively bigger.