They are not similar at all really. Autism is correlated to, "accelerated formation of neurons"(1) and "an increase in the number of neural connections"(2). That partially explains some savant-like traits being connected to autism. Outside of that John Travolta movie where he got the brain tumor and got super smart I don't think people are evolving tumors to increase intelligence.

[1] Article [2] https://medicine.wustl.edu/news/in-autism-too-many-brain-con...