[sometime lurker]

here in the US, non-vaccinating populations such as Amish and to a large degree homeschoolers have much lower (Amish is zero) autism rates.

It would be nice if that were true, but it isn't. A quick google brings up several sources debunking the "Amish don't vaccinate and have no autism" myth. See here.

[Scotswife]

And the Amish have their own health problems due to dangerous genetic disorders that get amplified when 2 carriers get married and pass it on.