A newly evolved gene is essential for efficient sperm entry into eggs in Drosophila melanogaster .

How fruit fly sperm enter eggs is poorly understood. Here, we identify a gene that potentially arose from non-protein-coding DNA and is required for efficient fertilization. Sperm from males lacking this gene's function cannot enter eggs. The gene appears to act during sperm production, rather than in mature sperm. This study illustrates how newly evolved genes can affect important aspects of reproduction and provides insights into sperm-egg interactions.