Earth gradually cooled, developed an atmosphere, and became potentially hospitable to living things by about 4 billion years ago. A mere 150 million years later, the earth was teeming with life. All of these steps in the formation of our solar system are now well described and unlikely to be revised on the basis of additional future information. Nearly all of the atoms in your body were once cooked in the nuclear furnace of an ancient supernova—you are truly made of stardust.
