Nitroglycerin and knife: what they have in common

1. Step 1. Nitroglycerin — is material for — Dynamite. Nitroglycerin in a porous filler.
2. Step 2. Dynamite — evolved from — Gunpowder. A replacement for gunpowder in mining.
3. Step 3. Gunpowder — is used in — Fire lance. A gunpowder charge.
4. Step 4. Fire lance — evolved from — Spear. The fire lance was a spear with a tube of gunpowder — the first step to firearms.
5. Step 5. Spear — has part — Stone tool. Early spearheads were made of stone.
6. Step 6. Stone tool — evolved into — Knife. The first knives were stone flakes.

Open Evothings