Slave Species?

One of the most convincing books I have ever read is the Slave Species of God by Michael Tellinger. He argues his case that we are the product of a genetic experiment by an advanced race of beings, who came to earth looking for some element needed to save their own planet. In the process, they decided to genetically combine their dna with the being found on earth, to get a race of slave who would do the work of mining for them. You have to read the book for yourself.