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How has the pace of human innovation changed over time? It took 260,000 years for humans to go from the spear to the bow-and-arrow, but only 42,000 years to go from the bow-and-arrow to the atomic bomb.

Students order and subtract integers to explore major milestones in human history and debate whether humans are innovating faster than we can keep up with the consequences.

### Students will

• Model “before zero” years using negative integers
• Order and position positive and negative integers on a number line
• Find the difference between integers, including negatives

### Before you begin

Students should be familiar at least with ordering positive integers. They do not need previous experience calculating differences between positive and negative integers nor ordering integers, though these activities are core to the lesson.