Apes still exist because humans didn't evolve from modern apes, but rather shared a common ancestor with them. Modern apes have evolved just as much as humans have since our evolutionary paths diverged. Your question indicates that you do not understand the basic concepts of evolution.. . Evolution is a scientific theory that explains the origin of the diversity of species (note that it does not, and is not intended to explain the origin of life). The basic idea of evolution is that mutations result in genetic diversity in a population, and consequently different traits, and different selective pressures favor certain traits over others. In a diverse population, some individuals are better suited to the environment than others, and the individuals that are better suited are more likely to survive to reproduce and thus pass their genes on to the next generation. Consequently, the next generation will have more of the "good" genes and fewer of the "bad" genes than the generation before it. Because the environment is constantly changing, the definition of "good" and "bad" genes is also constantly changing. Something that used to be an advantage can become a disadvantage, and vice versa. More often, however, neutral traits will become either good or bad. Changes in environment can include not only changes in weather or resources, but also competition from other species.. . As the environmental pressures change, the population of organisms changes with it. Over time, the little changes start to add up, and eventually the population will be so different from the ancestral state that it will be considered a different species. The diversity of species results from splitting of populations. If a population is separated by some geographical or reproductive barrier, the two subpopulations will likely evolve in different ways, to become two separate species. Eventually the two species may be reunited, but they will no longer be able to interbreed. Instead, they will compete with each other, and likely diverge even more.. . The theory of evolution is supported by considerable scientific evidence, and is accepted by the vast majority of the scientific community. It is the ONLY scientific theory currently in existence that explains the diversity of species. Some people claim that "intelligent design" is an alternative theory for the origin of species. However, intelligent design is not a theory in the scientific sense. It is not supported by scientific evidence and can never be tested experimentally (not because we don't have the tools yet, but because it is theoretically impossible). Intelligent design provides an alternative to science, not an alternative scientific theory.. . Science is not about finding a single piece of evidence to conclusively prove a theory. It's about constructing theories to fit the existing evidence and gathering new evidence that supports or refutes existing theories. Evolution is supported by a preponderance of evidence. While no one point conclusively proves it, when all the evidence is considered in the context of existing scientific knowledge evolution is a well substantiated theory. Intelligent design is not. What follows are brief explanations of some of the evidence that supports the theory of evolution.. . 1. Vestigial structures. . One example of a vestigial structure in humans is the appendix. It has no function. Removing it is harmful only in so far as any surgery is associated with certain risks (so I wouldn't have it removed just for fun, but it's because of the surgery not the absence of the appendix). An appendix is found in several mammals. In humans it is small and has no known function. In rabbits and many other herbivores it is large and is used in the digestion of cellulose.. . Another example of a vestigial structure is the hipbones of snakes. Snakes evolved from quadrupeds, and some species still retain not on pelvises,