[hindsightbias]

lead or lead lead?

https://en.wikipedia.org/wiki/Lead–crime_hypothesis

[marcosdumay]

Lead doesn't explain it, warmongering is something that has been high since ancient times, but airborne lead dates to the 20th century.

[hindsightbias]

https://arstechnica.com/science/2021/07/did-lead-poisoning-c...

[chownie]

Dietary lead in the form of sweeteners for wine plus a little abraded from cups and pitchers has been present since antiquity, so could still stand?