Contradictions

There is no homework posted and I was hoping for an opportunity to talk about this.

So this is the problem: in the old testament it states that the "law" is "life for life, eye for eye, tooth for tooth, hand for hand, foot for foot... Burning for burning, wound for wound, stripe for stripe." (Ex. 21:23-25) right? In other words, you have the right to get even. For example, you get robbed and catch the robber, you cut off his hand. (I think this is completely savage by the way.) Here comes the problem. In the new testament it states, "You have heard that it was said, 'An eye for an eye, and a tooth for a tooth.' But I tell you, do not resist an evil person. If someone strikes you on the right cheek, turn to him the other also. And if someone wants to sue you and take your tunic, let him have your cloak as well. If someone forces you to go one mile, go with him two miles. Give to the one who asks you, and do not turn away from the one who wants to borrow from you." as said by Jesus.

So how did we get from being so barbaric to being such pacifists? From this law of retribution(eye for eye) to having so much respect for everyone that you help them in some way. Having this contradiction, I don't understand how the Jews and Christians say they have something concrete as beliefs. Or have a foundation strong enough to be so popular. So common throughout the world.

I understand that as time passes, some things have to change. But what is the final decision? What is the verdict? What do they believe? How do participants in the religion justify one thing, if the bible says both?