Autism is characterized by number of behavioural problem with no eye contact, no communication with fellow human being. No request, like water, food. Child speaks like parrot. Human child should know how to talk but his that chip is missing.
Evolution of Brain:
After brain stem cerebellum developed. Cerebellum for controls, balance, coordination locomotion precision. Spiders and animal started walking. Then emotional brain developed. Brain stem, cerebellum, emotional brain (All neurotransmitter coming from emotional brain), cortex. Human brain is intelligent because it integrate everything.
There are two types of autism By birth and after birth.