Theories on the Origins of Humans

Almost every senior in my school is required to do a senior project at the end of the school year in which they research a topic that they're interested in.  I decided to research theories on the origins of humans, because it's something that's been on my mind for several years.  It's also a topic that is still hotly debated by scientists, religious advocates, spirituals, and others.  How did humans come to being?  Why are we so much more intelligent than all other organisms on Earth?  There are countless theories, some more valid than others.  The three theories I plan to focus on are the creationist theory, the Darwinist evolutionary theory, and the Ancient Astronaut Theory.

The creationist theory is my tentative classification of a collection of religions, primarily Christianity, Islam, and Judaism.  I'm not sure whether or not I'm going to focus on one of the three; I'll decide in time.  The creationist theory is the general notion that God created man in His own form some 4000 years ago (and holistically, God created the universe).  This theory is present in ancient texts such as the Bible and Koran, and is advocated in religious buildings today.  Creationism was a commonly accepted theory until around the mid-nineteenth century when people like Darwin began to question it. 

Darwin postulated that every organism on Earth evolved from a common ancestor, and the reason that certain organisms exist and most are extinct is due to reproductive success.  This is the evolutionary theory of natural selection, also sometimes called differential reproduction or "survival of the fittest."  Organisms that are the most successful in their niche will have more time to pass their selfish genes down to their progeny via sexual/asexual reproduction.  Thus, the most efficient (though nowhere near perfect) organisms are the ones that last.  Humans, then, evolved from primates for specific reasons, as indicated by current fossil records.  There's a lot more to it; I'm just summarizing.  A great book that goes into detail about this evolutionary theory is The Selfish Gene by Richard Dawkins.

The final theory, the Ancient Astronaut Theory, is the one that is commonly thought to be the most farfetched theory of human origins.  Yet for some reason, I seem to believe in it, though that might change after I finish this project.  The Ancient Astronaut theory postulates that extraterrestrials came to Earth a very long time ago and as an experiment, mixed their DNA with primates to produce intelligent humans.  The evidence that suggests this lies in the ruins of ancient civilizations.  Incredible structures such as the Great Pyramid and Stonehenge are examples; some people believe that there was no way that humans could single-handedly build these structures.  If you read up on the architecture of these structures, it makes sense why people would think this. 

So which theory is right?  Who knows.