How do you think it all came about? Here's a very rough summary of my understanding:
13.7 +-0.2 billion years ago, the universe as we know it began expanding from an extremely hot and dense state for reasons unknown. 4.6 billion years ago, a cloud of primordial gas, seeded by the nuclear ash of several generations of supernova and likely compressed by the shockwave of a nearby supernova, collapsed to form the solar system. Part of the mass of the cloud formed the Earth 4.54 billion years ago.
The first prokaryotes appeared approximately 3.7 billion years ago, having evolved from simple self-replicating chemical systems after the end of the late heavy bombardment, and the last universal ancestor split into the bacteria and archea 3.5 billion years ago. Photosynthetic cyanobacteria evolved 3 billion years ago, oxidising the surface to form banded iron deposits which are mined today, and causing a slow buildup of oxygen in the atmosphere once the surface had been depleted of oxidisable minerals.
1 billion years ago, the first multi-cellular organisms evolved. From there, evolution became more rapid, with simple animals appearing 600 million years ago, arthropods 570 million years ago, fish 500 million years ago, land plants 475 million years ago, amphibians 360 million years ago, mammals 200 million years ago and humans 2 million years ago.
Behaviourally modern humans appeared in Africa 130,000 years ago, and a dramatic increase in technological development began 50,000 years ago. Human societies increased in complexity and formed the first human civilisations approximately 10,000-12,000 years ago with the development and spread of agriculture and the glacial retreat which provided optimal conditions and virgin land. The population and technological progress both began exponential explosions that have continued to this day.
Anyone have a different interpretation? (Significantly different; not minor quibbles about details.)
