As alarm grew over autism prevalence at the turn of this century, there was much public talk of a growing “epidemic.” That language has since softened, and it is now clear that many autistic people were there all along, their condition unrecognized until relatively recently.

But what is the cause? The emerging narrative today is that there is no single cause — rather, multiple factors, roughly sorted into the categories of genetics and environment, work together in complex ways. Becau