There's new progress in the quest to figure out why autism occurs. Different teams of scientists, working independently, found that several children with autism had mutations in the same genes. The mutations are genetic glitches called de novo mutations—they're inherited, but occur during conception, and they're usually harmless. They're also increasingly common as the parents increase in age. The mutations discovered account for a fraction of autism cases, but the findings point a way forward for future research. Some experts say further research could turn up mutations that account for 15 to 20 percent of all autism cases.