[rwyinuse]

For vast majority of human history most people spent their days doing fairly simple physical work, which didn't require that much sustained focus compared to what an average knowledge worker needs today. Obviously they didn't have smartphones, computers and other forms of distraction either. So really it's quite obvious that most people with ADHD would have done much better in such environment, compared to the unnatural mess we live in today.

So, people with ADHD have always existed, but it's our modern world full of distractions and unnatural work which makes it a much bigger deal than it would otherwise be.