"Earth is about 4.5 billion years old, and early forms of life were definitely on the planet by 3.7 billion years ago. That bare fact seems to imply that it was

"Earth is about 4.5 billion years old, and early forms of life were definitely on the planet by 3.7 billion years ago. That bare fact seems to imply that it wasn’t hard to get life going on Earth; if initiating life was really improbable, then we should have had to wait a long time before its appearance." I think it's a significant observation that there's just a single origin of life -- that after a 4.5 Gy sample time, we only observe one type of biochemistry. If you predict abiogenesis happens easily, you should expect it to have happened again independently, many times, and expect to find distinct classes of radically different, "alien" life on earth.