Zecharia Sitchin's theory of the origins of man, laid out thoroughly in his book Genesis Revisited, is controversial, to say the least. He skillfully combines both sides of a heated debate on how, not only man, but the universe came to be. The idea he proposes is an ingenious mix of equal parts evolution and intelligent design, a liberal dash of mythology, and a smidgen of Biblical history. The result tends to upset people on all sides of the argument, since all see it as a form of heresy of their belief system.
His thesis proposes that evolutionist have it right for the first several billion years. Except, on another planet, Nibiru, the evolution process got started sooner. This led to an exceptionally advanced civilization, the Anunnaki, who, around 450,000 years ago, needed gold to save their atmosphere. They came to earth, hoping to mine enough gold out of our planet to save theirs. However, they decided it would be easier to create a worker, a primitive species that would labor indefinately. With this in mind, they spliced some of their genes with the chimpanzees of Earth, to make humans. Homo sapiens, their created work force.
I have several problems, some logical, some ideological, with this theory. First and foremost, is this strange mix of intelligent design and evolution. If humans are too advanced to have evolved on their own, how could the Anunnaki have evolved? Was that with the help of another alien species who created them? If so, how did they evolve? This sets up a nasty little series of circular reasoning. All this does is push back the question of how it could have evolved.
Secondly, he bases much of his theory on Sumerian Texts, which he claims are the basis of the Bible. The problem is, the Sumerian texts go into great detail, adding all sorts of things to the Biblical version. If you think about the party games Telephone and Round Robin, where one person comes up with a sentence, and it gets whispered around the group, at the end, it's far more complex than it starts. People always add details trying to make their version seem more realistic. Therefore, the simpler texts are usually the more accurate ones, not the other way around.
My ideological problem with this is Sitchin's use of the Bible as proof for his theory. I am a Biblical Literalist, in that I believe the Bible is literally true. Not to say there aren't mistranslations, as that is inevitable, but I believe the KJV is mostly accurate. To use a book that so thoroughly denies his ideas as support is heretical, to say the least. The Bible's whole message is that Earth was created for man, and we were created in God's image. God loves and cherishes us, and wants to save us from ourselves. And Sitchin refutes this with the idea that we were created as nothing more than cosmic slaves, the playthings of some malevolent aliens.
In conclusion, to some people this will be the perfect answer to the question of how things came about. It will answer how man was able to evolve from apes, without the insertion of a God. To others it will seem absurd, and will be written off completely as the ravings of a lunatic. Still more people will see it possibly as slightly heretical, but possible. It has been well researched.
I encourage people who are interested in this to thoroughly read up on it. Genesis Revisited is the main book outlining his theory. Good refutations are Jonathon Grey's The Killing of Paradise Planet, and the books by Immanuel Velikovsky. This is an extremely interesting subject, and one that should be explored by all.