>> Life appeared on Earth early pretty much as soon as conditions arose that would support it (as soon as the planet cooled enough). So that would point to life

>> Life appeared on Earth early pretty much as soon as conditions arose that would support it (as soon as the planet cooled enough). So that would point to life being "easy" to form. >That's quite a stretch. What is a stretch? That life formed as soon as conditions supported it, or that it may indicate that life is easy to form? The earth formed 4.55 billion years ago, the moon formed 4.5 billion years ago, and 4 billion years ago was the end of the late heavy bombardment, and the first formation of life. I do agree that changes in conditions could prevent a second biogenesis event, but there seems to be enough time with the initial conditions that it "should" have happened more than once. But that is just my initial impression from the simplified versions of geologic timescales that are presented in various pop sci media.