Michaux velocipede and stone tool: what they have in common

1. Step 1. Michaux velocipede — has part — Crank. Cranks on the wheel axle.
2. Step 2. Crank — is part of — Meat grinder. A handle.
3. Step 3. Meat grinder — has part — Knife. A cross-shaped blade.
4. Step 4. Knife — evolved from — Stone tool. The first knives were stone flakes.

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