In the last ten years, countless personal genomics companies have popped up. From 23andMe to Family Tree DNA to Ancestry.com, these services mostly focus on health markers and genetic genealogy. Undoubtedly, those are excellent uses for genetic tests, but that isn't the complete story of the human genome. Inside the cells of every human being on earth lies the key to understanding our shared history as a species. As it turns out, we can use our genes to help track every major migration that humanity has ever experienced, and it's just now starting to get interesting.