Science has yet to prove that we are descended from apes, they can't seem to agree on that subject, I've heard many options, sea otters, chimps, and something else, I can't remember.
The scientific evidence suggests that humans and modern apes have a common ancestor. Chimps and bonobos are our closest living relatives. If you think of a family tree, I would say that my cousin and I are have grandparents in common. Or in other words, we are descended from common ancestors. I would not, however, say that I am descended from my cousin anymore than I would say that humans are descended from chimps.
DNA fingerprinting in humans to determine paternity (and to match a victim's and suspect's' blood to a crime scene) works because relatives have fewer DNA differences between them than un-related people do. Likewise, humans have DNA that is 99% identical to chimps. There are a few more differences between humans and gorillas, orangatuns and other great apes.
Remember when I told you that some genes are found in all living things. These core genes pick up changes very slowly because they are so critical for life's functions. If you compare the DNA sequences for one of these genes, say cytochrome c, you will see that there are fewer differences between humans humans, apes, monkeys, and other primates than there are between humans and other mammals. The number of differences increases as you go from mammals to reptiles to amphibians to fish to protozoa to archeabacteria to bacteria. This gene has the same function in all of these organisms, so you can't say that you expect the gene to be more similar in organisms that look alike than in those that don't. The only logical explanation is that the orginal cytochrome c gene has changed slowly over time and that those organisms that have more similar sequences shared a common ancestor more recently than those organisms with more differences.
Some additional information:
http://evolution.berkeley.edu/evosite/e ... nies.shtml
http://evolution.berkeley.edu/evosite/s ... mit=Search