Chemistry got started and
Single cell organisms formed 3.8 BYA on Earth. That was the beginning of Biology. A billion years later, 2.8 BYA, multicellular organisms formed and life arrived.
A tree of life from common origins:
You can spend a lifetime examining the development of life on Earth. You can do that on your own, if you like, but I will move on and I’ll start talking about the Fictions that Homo sapiens created and how these fictions shaped and are shaping the world we live in.
For the first hundred and forty thousand years Homo Sapiens were foragers and they knew home and not home. About 10,000 years ago, we entered the world of agriculture. There is an ongoing debate about whether this agricultural revolution helped or harmed us, but it happened. That led to Homo sapiens building cities and empires of thousands of citizens, far more than humans could have built before the Cognitive revolution.
It was now the time for fictions to shape our world’s history. During these fictions, Homo sapiens built history.
We built ancient societies in China, India, Egypt, Persi and through the steppes of Mongolia. But in Classical Greece (800 – 200 BCE), Homo sapiens built a mythology of Gods and heroes that led the Athenian society to develop the idea of a Democracy. Athens was a polis or a city. It had about 33,000 Greek foreigners and 100,000 slaves living together with about 100,000 citizens. Of these citizens, all men over the age of 18, about 30,000, were voting members of the government. The people were the demos and they had the kratia or the power. It was a government of the people and ruled by the people. In my opinion, Democracy has been the best government Homo sapiens has ever created.
It was here, that the philosophers discussed the nature of the world. They believed it to be intelligible and even determined that the Earth was a sphere. Observing lunar eclipses played a role in ancient Greek beliefs about the shape of the Earth. They deduced that it must be a sphere from the shape of Earth’s shadow on the moon during an eclipse. Watching ships sail off and disappear over the horizon, they noted that the sails disappeared last and appeared first when the ship returned. This would happen only if the surface of the Earth was curved.