I'm pretty sure about the cause of autism. In 2001, I proposed the Neanderthal theory. It's since been confirmed in various ways by online surveys and other findings.
As for the discussion about racial prevalence of ASDs, there is no published study which confirms that all ethnic groups have the same prevalence AFAIK. There is a study in special education that compare various groups in the US, but it is not reliable - [ rest of paragraph removed by moderator]
However, in Aspie-quiz 6 & 7 I've researched autism prevalence in the US. It turns out that Asians and American Indians have about half the prevalence of Caucasians while Afro-Americans have about 1/6th. The finding for Asians and American indians could be the result of social factors, or even a chance finding, but the 1/6 prevalence of Afro-Americans is very solid. Aspie-quiz 6, racial prevalence, Aspie-quiz 7 - racial prevalence
