Whether autism is an "step" in evolution, I do not know.
But I would absolutely say that an all Aspie earth would work wonderfully.
I mean, we do not know how to behave because we have no point / person of reference. We are raised in an environment where everything is designed the exact opposite way of how we need it to be. We have no aspie peers as kids, no aspie parents who would tell us how to live with our "condition".
And now that Asperger's is seen as a real thing, look at the kids who get therapy early. They totally "pass".
If everyone was an aspie (parents, teachers, politicians etc.), there would be no need of "autism specific therapy".
As kids, we would just learn and accomodate naturally by looking and learning from other autistics (parents, older siblings, teachers, movies etc.)
There is no problem with asperger's, it's the unfit environment we grow up in, and if autism is an step in evolution, I can totally see it working. The world just needs to reinvent the wheel, because almost all the "old" rules and psychology and social norms just do not apply, and different ones must be created and put in place, which will probably happen quite naturally (in the case of all autistic world).
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Male
Aspie score: 131 of 200
NT score: 34 of 200
Possibly Aspie (diagnosed by an autism expert, doc moves abroad, forced to change docs and all say it's schizophrenia NOS or schizo-affective disorde or personality disorders. initial doc was a colleague of uncle Simon btw. you do the math.). (edit: by Uncle Simon I mean Simon Baron Cohen. Just to clear things up.)