A brain-development gene found exclusively in humans has an unusual evolutionary history and could contribute to what makes us distinctly human. Equally surprising, this is a partial gene created from an incomplete duplication of its parent gene in the prehistoric human genome. The incomplete duplication of the gene may account for its behavior. This may have been some ancient error which was reproduced successfully. Deoxyribonucleic acid (DNA) is a nucleic acid containing the genetic instructions used in the development and functioning of living organisms. The DNA segments carrying this genetic information are called genes. Likewise, other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information.