Do you think that autism spectrum disorders are a side effect of mutations intended to increase intelligence?
No. Autism is a complicated and mostly environmentally created learning disorder. Causes can range from bowel disorders to oversensitivity to certain chemical combinations. Some of these have proven treatable, others have not. They appear to have more intelligence because some of them are autistic savants, capable of extra ordinary focus in a single area. However they are still socially very maladapted and there is no reason to believe that there is an evolutionary advantage to this.
