Wheel

In the OLD days, the wheel was invented, but it has a partner: an axle. How the heck should I know when it was invented? But it also tends to help chariots move in Ancient Greece. Now, if wheels dissapeared, then the Gear would disappear as well, because the gear is a wheel that has teeth, and even pulleys would disappear. Sleds and horses would be SUPER DUMB, so you should know that the wheel is important.