inventions?

I would say its the written language. Spoken language evolved, but written must of been invented on purpose. If it was not invented, no information would be passed undirectly.

DXdad has a point. Without the wheel there would be no plastic because the machines that make the plastic in factories have lots and lots of wheels. But I would have to say...refridgeration. To me, refredgeration is so important these days. Eventhough the motor that turns the compressor spins in a circular motion and the motor itself was created in factories that use circular wheel-like machines to produce them. Thank god for refridgeration. Also...along with refridgeration comes air conditioning and freezing.

It's the wheel.

That's my opinion anyway.

Without it we'd never have invented any form of transport other than walking and would therefore still live like cavemen.