Nature Reviews Genetics 14, 645–660 (2013)

On page 655 of the above article, the sentence starting "Indeed, for male-expressed genes..." was corrected to state that X→A gene traffic by DNA-based duplication has been detected in Drosophila spp. and Teleopsis spp. Also on page 655, the sentence starting "Strikingly, transcriptome analyses of the human brain..." was corrected to state that the region of the human brain which showed enriched expression for new genes was the prefrontal cortex. On page 656, in the opening paragraph of the Evolution of essential functions subsection, the text was adjusted to clarify that neofunctionalization is also a possible route to new gene essentiality and that the findings of reference 46 are consistent with a process of neofunctionalization rather than subfunctionalization. Finally, in Table 1, the reference was corrected for the Pros28.1A gene. The article has been corrected online. The authors apologize for these errors.