It's hard not to say "genetic". I'm sure my dad and his mom have it. It probably ran on my grandma's side of the family. Both of my kids have it.
But here's the deal, I think a lot of people on the spectrum with more severe symptoms have other conditions that may affect their functioning. I think Autism may be considered a combination of disorders in some cases. And all those disorders or even illnesses influence each other... not sure how else to say this
like in my younger son's case. I think his processing issues are much more severe than mine but it seems there's the same pattern. And I believe the combination of genes he's got from me and my husband may altered the way those difficulties manifest themselves in him. I'm not denying that some environmental factors may have altered the manifestation... but then again - nobody knows. I give one little example. I couldn't recognize speech very well until the age of 5 and with some words till 7. I could speak (starting with a few words probably at the age of 2 and full sentences around age of 4) but when I heard other people talking sometimes it sounded like gibberish to me. I was fascinated by that gibberish and really wanted to figure out how those words really sounded like, what they really were (I actually knew those words mostly, but I didn't recognize them). Maybe my great interest actually motivated me to figure it out and eventually helped me to hear it right. Now it seems to me that my son may have similar issue, but for him it's also hard to pronounce words. But that may not be due to Autism but due to Apraxia. He seems so similar to me, but his symptoms (that at some point were mine) have been altered.
In the future I see Autism being split in many different symptoms; those symptoms are addressed separately and only jointly when it's appropriate.
But here's the deal, I think a lot of people on the spectrum with more severe symptoms have other conditions that may affect their functioning. I think Autism may be considered a combination of disorders in some cases. And all those disorders or even illnesses influence each other... not sure how else to say this

In the future I see Autism being split in many different symptoms; those symptoms are addressed separately and only jointly when it's appropriate.