From this long but interesting piece in National Geographic regarding twins, the genes vs. environment debate and the New Kid on the Block in the debate - epigenetics: "Scientists are only beginning to understand how epige­netic processes relate to complex disorders like autism. The good news is that some of these processes, unlike our DNA sequences, can be altered. Genes muted by methylation, for example, sometimes can be switched back on again relatively easily. And though it may not happen soon, the hope is that someday epigenetic mistakes will be as simple to repair as a piano that's out of tune."