This is a bad question, and a trap. We have a recorded history that is only a few thousand years old and even that is not long enough for the kind of drastic speciation that has occurred throughout earth's long history. We can show you countless examples of observable changes within species through different methods that demonstrate the basic function within evolution. Take for example dogs, which we know are descended from domesticated wolves. We breed dogs in specific ways to create all kinds of differing breeds that accomplish varying purposes for us. This is an example of artificial selection, and has been a method used by humans to domesticate pets, livestock and even crops and fruits. We are basically using the same biological mechanism without our DNA to manipulate the breeds of dogs as nature accomplishes through natural selection, we just do it through sexual selection.
Obviously you can observe the difference between a poodle and a wolf, yet we know that poodles are a man made breed accomplished in the 15th century. Think about that, poodles didn't exist until the 15th century. That means they must have come from another breed of dogs, and that breed of dogs must have come from another breed of dogs, and those dogs may have come directly from wolves... then you keep moving backwards and you see evolution in action. Evolution isn't something that just happens in a flash, it is about small incremental changes within a population geographically separated from another that causes little by little genetic shift until one day you have an entirely new species that may not be able to even breed with the former species.
It's interesting stuff!