In the first 20 minutes of 2001: A Space Odyssey you see a group of monkeys going through evolution. The first change you see is that of a leader. In the beginning, each monkey did their own thing, and was not bound to any organization whatsoever. The monkeys did what they want when they wanted. Then the change begins. A single monkey, by himself, rises to the top of a cliff. He stands and screams. The other monkeys notice him screaming and began dancing and rejoicing. They scream and jump around, in what appears to be reverence for their new leader.
Stanley Kubrick shows the change very simply, yet its message is still very clear. The monkeys had never shouted as loud or danced as much as they had previously in the film. Their actions confirm that something in fact had changed. The second step shown in these monkeys evolutionary progress is that now these animals appear to be goal oriented. Like mentioned previously, these monkeys had been working for themselves. They would do what ever they could to benefit themselves, get food, and have a nice place to sleep.
Yet, once the changes begin and they have a leader, the monkeys begin to act as a group. They are more coordinated and it seems that their living style has changed from anarchy to monarchy. They attack a larger animal and kill it as a group. In turn, the raw meat is then split between the monkeys and everyone gets a share. The third and probably most evident change is the monkeys use of weaponry. One of the monkeys noticed a bone as he walked around the land. He picked it up and examined it. Then gradually he starts to hit it against the ground.
The monkey starts to break other bones around him as he hits harder and harder. The discovery of the first weapon is made. Then you see the group of monkeys with the weapons begin to invade another group of unarmed monkeys. They conquer the territory and take it as their own. The physical interaction between the groups of monkeys is really the first form of war. Kubrick is showing how quickly war came into the picture and how scary that even primitive apes have the ability to kill other animals to get the land they want.