Four periods of history

Pre-cambrien, paleozoic, mesozoic, and cenizoic.

These, when spelt correctly, are some of the geological eras of our planet.

Mammals and indeed humans have been around for a very small part of that time. We appeared, I think, in the Neolithic; which u forgot.

It's said that history is what's happened to humans.

Some folks suggest that there's pre-Stone Age, before we'd learnt how to shape flint into knives; Stone Age, when we could do that, and throw rocks at each other. Fire will have been tamed then. When we almost built the Tower of Babel. The Bronze Age was when we could get enough heat to melt copper and its impurities into bronze and brass weapons. Think Siege of Troy. The Iron Age came next, using charcoal and, later coal. The civilized discovery of the world. Our first literate king, gay King Edward II, is a part of it. Now we have the Electronic Age, in which knowledge is the key; everything is on plastic, and we have computers to translate languages and send messages into space. That's five, not four; but they seem useful.