The horse bit and bridle kicked off ancient empires – a new giant dataset tracks the societal factors that drove military technology

Intro:

Starting around 3,000 years ago, a wave of innovation began to sweep through human societies around the globe. For the next millennium the continued emergence of new technologies had a dramatic effect on the course of human history. This era saw the advancement of the ability to control horses with bit and bridle, the spread of iron-working techniques through Eurasia that led to hardier and cheaper weapons and armor and new ways of killing from a distance, such as with crossbows and catapults. On the whole, warfare became much more deadly.