Evolution has more evidence and a stronger foundation than the theory of Gravity, you only accept it because you can drop an apple and see that it falls. However, evolution doesn't work like that. Scientific research on chromosome 2 proves we share our closest ancestor with chimpanzee's. It is a fact that we have a common ancestor with them, and all other life on Earth. It is a fact that species change over time, and species evolve into a new one over many many years. This has been directly observed to happen with Darwin's Finches, salamanders in California, and even more for certain with fruit flies.