How Life Started

How life started is a very big question. All answers, including those proposed here are strictly hypothetical. This is because nobody was present 4 billion years ago to witness how life started and because there are no first life-forms alive on Earth today. Yes, the earth had to cool down and form a solid hot mass before life had a chance of starting. That limits us to around 4.2 billion years ago (BYA). Furthermore, the atmosphere needed to change from hydrogen and helium to a volcanic atmosphere of carbon dioxide, carbon monoxide, nitrogen, steam, methane, and ammonia before life had a chance to start. That change occurred around 4.4 BYA. The Earth's volcanic onslaught possibly needed to stop as did the bombardment of Earth from space by comets and meteorites before life could take a grasp. They both stopped by around 3.8 BYA.