So I’ve been thinking, please keep in mind this has no real scientific basis it’s just what my brain was thinking when I couldn’t sleep the other night.
Some of the traits often associated with ADHD are impulsiveness, curiosity, thrill-seeking and being easily bored. These traits would have been a double-edged sword to our ancestors, the primitive humans that got bored with their current setup could seek adventure in new places and find new sources of food, new territory and come up with new inventions and innovations. They were also probably more likely to stumble into predators because they wanted to see what was on the other side of the mountain or eat the wrong berries because they looked tasty or set themselves on fire while experimenting.
What if the anxiety that sometimes goes hand in hand with ADHD evolved in parallel as sort of a braking system, the stronger the impulse to go do all the exciting stuff the stronger the force needed to reign it in. It might make them a bit more jumpy when they see a bush move or hear a rustling sound and less likely to get eaten than someone with a strong desire to go check out that interesting tree over there and no fear of the big footprints nearby. It was probably really helpful to our primitive ancestors, but without sabertooth tigers all over the place to protect us from it’s manifesting in other ways and messing with our heads.
This is just my silly random thought that occurred to my sleep-deprived brain!