What is the cause of Asperger's?

I was doing research, and saw that there are things that people with asperger's tend to have in common...

1) excess of synaptic connections between neurons in the brain

2) gastrointestinal defects

Does anyone have a theory of why these things tend to coincide with lack of social awareness in people with Asperger's?

What is the cause of Asperger's?
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