I am a 3rd undergraduate and am doing a bio major. But for large changes to occur there has to be a small population. Smaller populations have a smaller gene pool which leads to many more mutations. I think on the scale that you are referring to there would have to be an extinction of species. This would lead to many micro populations to have mutAtions leading all leading to a larger, more stabilized gene pool. There are also two ways these extinctions can occur and they are known as contingency and convergence these are left up to chance and not controllable. Also natural selection is the mechanism for which evolution can work. There are many, many different variations of natural selection ex. Survival of the fittest, mutation, sexual selection, convergence, contingency, etc... Very cool post though I enjoy learning what people have to say on this subject as long as there answer isn't God created everything