The human genome draft sequence released in 20011,2was a consensus sequence based on the stitching together of DNA sequences from clones derived from many individuals; at best, this corresponded to an imperfect sketch of the human sequence and certainly represented no one person. The immediate utility of the human draft DNA sequence was that it provided a map to allow scientists to localize genes that were mutated in mendelian disease. It did not directly help us to understand the more subtle differences between us, including predispositions to the many common diseases that afflict humans. These common diseases, which include most cases of neurological disease such as most amyotrophic lateral sclerosis, Parkinson disease, Alzheimer disease, stroke, brain tumors, many other cancers, most heart disease, and type 2 diabetes, have been believed to be predisposed to by many common variants across our genome. It has been believed that much human disease had its roots in individuals with unfortunate combinations of variants in different genes across their genome, perhaps with exposure to predisposing environmental factors and possibly a little bad luck, too.