No one really knows how probable abiogenesis is. The fact that we are complex, sentient life forms within 13.8 billion years of the beginning of the universe se

No one really knows how probable abiogenesis is. The fact that we are complex, sentient life forms within 13.8 billion years of the beginning of the universe seems improbable, especially considering that life on earth spent 2.5 billion years of its 4 billion year history as single-cell organisms. However the complexity of life appears to be accelerating. The earth is only 4.5 billion years old, so it only took 500 million years for life to form on earth, even less when you consider that the cooling of the crust was necessary.