working9while5 - Actually, there has been some recent research papers (can't find the links right now though) that shows that there is both a structural difference in the brains of people diagnosed with Autism AND another research paper that shows a deletion on a particular chromasome in the majority of people with Autism in the studies. We are coming ever closer to finding the physiological reasons for Autism, thanks to medical advances.
I'm quite sure that in 30 years time, we will KNOW what causes Autism. And IMO, there IS a genetic link in at least some cases. In my family alone, 50% of the last 3 generations have a diagnosis of some form of Autism, totally independantly, diagnosed in different hospitals, by different teams of Doctors, with no connection between the 'patients' as they ALL have different surnames.
My Maternal Uncle was diagnosed in adulthood (in his 40's) with Aspergers Syndrome. My Dbro was diagnosed with Aspergers BEFORE his Uncle, when he was 7yo. My Dbro was the first person in the family to get a diagnosis, and it triggered my Uncle to go for tests. When my DD was 4yo, she was diagnosed with HFA (High Functioning Autism) - this was 4 years after my Dbro's diagnosis - which at the time, I had NO knowledge of, as I wasn't even in CONTACT with my maternal family AT ALL. I then had two more dc, and my 3rd DC, my DS2, was ALSO diagnosed as being 'on the Autistic Spectrum' when he was just 3yo. A mere 4 years after my DD's diagnosis.
It didn't help with my DS2 that as WELL as my dodgy genetics, his FATHER had been diagnosed as Autistic when he was 12yo, and attended a SN school for dc with Autism...so poor DS2 got dodgy genetics from BOTH parents!
I DO take great offence at people that say that environmental factors cause Autism. When it just ISN'T the case.
Environmental factors may cause children to display some similar behaviours to someone with Autism - but they still don't necessarily have Autism. Unless they do - in which case their environment wouldn't have changed that! A crap environment won't CAUSE Autism - but it will stop a child with Autism from progressing in the same way they would in a loving 'normal' environment. There IS a difference!