Its possible autism was more widespread in the 1700s-1800s. And with increased social circles it diminished. And today its increasing again for some other reason. Some kind of 'Autism Laffer Curve'.
Thus the "odd fellow" out on that remote farm may well have fallen into what today goes for mild end Autism, or Aspergers, but functioned because the farm life was mostly self sufficient.
Sometimes i wonder how many of the old west mountain men were on the mild end, and opted for a life away from society.