Read the most advanced science of autism causes here. Bypass the commenterati and go direct to the science. Don't waste your time at the sites which pretend "no-one" knows what causes (or what sometimes cures) autism.
This is a website relating to the unchallenged theory of autism, IQ and genius, Personality and Individual Differences 14:459-482 (1993) by Robin P Clarke (the antiinnatia theory). An update review paper is being prepared for publication. Meanwhile you can download the original 1993 publication (presentationally revised) here, and the original 1993 publication (author's reprint) here . (the journal site version is here:, but without added charts of social class and you may have to pay Elsevier $31.)

Age of Onset graph

First graph is from the Autism Research Institute (though named "Institute for Child Behavior Research" during most of this graph). Second is my re-working to show the changing ratio of age of onset. How easily is this data compatible with no increase?