I understand it's animated but all they did was change the structure of the monkey's pelvis so he can stand upright.
The general belief is that our ancestors, after encountering snow, stood upright so their bodies are farther away from the cold ground. Caesar was sprayed with smart juice. But the effect was apparently the same.
Gyro, it is more commonly believed that humans stood up straight to get a better view of the surrounding area after tall grass appeared. The homos that decided to stand up straight were able to walk from the far spread trees in the grasslands more safely than the others.
actually, two* simians were fighting and one landed a solid uppercut on the other, thus making it stand, then others tried to do it.
The Arguement of The Ages begins... In the right corner is PieSquared761 with +4/-45 In the left corner is Sharqman with -24/-128
early man stood up because they wanted to be able to move to other area's quicker to get food, and to avoid predators. *or they were nomadic padaun's running from the pieasaurus rex*