Actually scientists do know that we humans share a common ancestor with chimps. The theory of evolution dictates that through the process of natural selection we have slowly mutated from single celled organisms to where we are today. Evolution is not a direct process. Think of evolution as more of a huge family tree than a direct linear line of your immediate family members. A mutation is a deformity. We can see these in people today. Most of the time these mutations are non beneficial, but sometimes depending on the creatures environment the mutation may help he creature with survival. This creature with the "superior genes" will be most likely to reproduce an pass on it's genetic code. This process has slowly gone on on our plane for billions of years. Only in the past few million years have Chimps and other animals appeared on the earth. We humans back a long time ago had a common ancestor. Going back to the family tree analogy you could think of a chimp as humanity's distant cousin. We did not only come from apes though. We have many other ancestors. Depending on how far you look back in the timeline of life on earth. If you go back about 3.7 billion years ago you may find the first living organisms. All living means is a reproducing molecule so it wouldn't be anything extravagant but it would be enough. On the other hand if you look at life today you see how diverse and beautifully complex life on earth is. We Are a result of that one reproducing molicule.
