Sledge and oil lamp: what they have in common

1. Step 1. Sledge — evolved into — Cart. The wheeled cart replaced drag sledges and sleds.
2. Step 2. Cart — has part — Axle. The wheels turn on an axle.
3. Step 3. Axle — is part of — Yo-yo. The axis between the discs.
4. Step 4. Yo-yo — is made of — Clay. Greek yo-yos were terracotta.
5. Step 5. Clay — is material for — Oil lamp. Later — clay ones.

Open Evothings