Evolution is the brainchild of a man named Charles Darwin. It was originally conceived by him on the ship HMS Beagle from 1831 - 1836.
While in the island chain Galapagos Archipelago Mr. Darwin observed interesting discrepancies between finch species. Some finches had curved beaks for probing flowers, while other had long straight beaks, which appeared to have been designed for drilling holes in wood for insect food.
Previously any scientist observing this discrepancy would have assumed that God had simply designed the finches differently, so they would not have to share the same food source. Darwin postulated something different. He suggested that perhaps once in a while a finch would be born with a slightly different beak than its parents. This beak may have been better designed for acquiring food than that of the other finches in the area. Now let’s say during the lifetime of this finch the food supply became scarce for some reason or another. While the other finches may starve, the finch with the special beak would have an alternate source of food. This finch would survive and reproduce.
Now although genetics had not really been introduced to the world at that time, it had been observed that offspring often inherited traits from their parents. Mr. Darwin hypothesized that some of the offspring would be likely to share this (no longer quite) unique feature. Should the period of low food supply continue into their lifetime, or should another one occur, the offspring with the trait would be more likely to survive and produce another generation. This time however the offspring produced are more likely to have the specialized beak, especially since chances are higher that both parents will have the desirable trait. The chance of this happening increases over time, so eventually an entire new race of finches will appear, all with the specialized beak. What happened to the original species? The food shortage probably did not kill them all off, and once the problem is resolved it is more than likely their population climbed back to it’s previous level. Perhaps they migrated to another island, one more abundant in the resources they require for life.
While this theory is sound, it doesn’t account for finches turning into a completely different species. Mr. Darwin theorized that perhaps, over many, many generations, changes like this would “pile up”. One resource shortage might cause a change in the race’s predatory weapons, allowing them to hunt different types of prey. But this new prey might be harder to digest, leading some time later to the development of different digestive and eating organs. Perhaps this prey is fast so new legs need to be developed. And enhanced intellect certainly has no considerable disadvantages. So these changes keep on piling up, until one day, you have something so wildly different from the original species that it can be classified as an entirely different creature.
This, the theory of macroevolution, is the most widely accepted explanation for the diversity of life on Earth. However debate continues to this day about its accuracy, and recent discoveries in numerous fields cast serious doubt on macroevolution’s future as a serious theory, therefore this author shall certainly not attempt to reach any conclusion in the bounds of this document. The goal of this document was merely to overview the theory of evolution from an objective point of view, and that being accomplished, is now concluded.