Transportion

When early humans moved from place to place they had to walk. If they needed to move something, they had to carry it. Heavy loads were dragged on slegdes, and animals, usally oxen, were used to help. If the load was very heavy it was placed on rollers made from tree trunks. This was a very slow job until, about 5,000 years ago, the wheel was invented.
The first wheel was probably just a slice from a log. This would soon crack and split.
A wheel made of different pieces would be stronger, but very heavy. It was a long time before the spoked wheel was thought of. …