[SaberTail]

I think it's at least plausible that ADHD traits could have been useful in the hunting and gathering environment humans evolved in. Being more inclined to pay attention to new things in your environment might make you more likely to discover threats and new food sources. Being able to hyperfocus might be useful if you are practicing persistence hunting and following prey for hours. These traits become a "disorder" because they're not as well suited to capitalist modes of production.