Suppose there are many different ways for the universe or multiverse to evolve intelligent life. There will be easy ways to evolve intelligence and difficult ways, and these ways will fall on a spectrum as such. In fact, it is reasonable to suppose that this spectrum can be plotted as a frequency distribution and will be a bell-shaped curve. Where would humans fall on this curve?
Before answering this let’s pay homage to the debate of the Anthropic Principle. This principle states that the universe is geared towards producing us. It is derided by modern scientists because it seems like cosmic hubris. Since the time of Copernicus, we have been moving away from this thinking starting with the heliocentric model of the solar system. In keeping with this trend the latest proposal is the multiverse which solves the problem of fine-tuning of physical constants. This change in thinking is called the Copernican Principle, or Principle of Mediocrity, and would suggest that we are most likely an average way to make intelligent life. We are not found at the tail ends of the bell curve, rather smack in the middle. Earth-like biology is probably a rather easy way to make intelligent life in this universe/multiverse. Applying the Principle of Mediocrity, the frequency of earth-like complex life, is a surrogate marker for the frequency of intelligent life in the universe. That is very important because we can actually say something about the possibility of earth-like life out there. What does science say? How difficult is it to make earth-like life?
If you think we are in an infinite multiverse where all possibilities become actualities, then this question might be of less importance to you. Because even if it’s one in a zillion zillion, there ought to be an infinite number of earths out there in the multiverse. This is theoretical physicist Brian Green’s take on the matter. There is another Naïve Thinker out there but who is actually the President of Mars, but this doppelganger must be almost infinitely far away. If you are going to be this generous with reality, you will run into a problem. If absolutely everything possible is actualized, then God must exist. And, an all-powerful being would also be God of the whole multiverse. Also, the Flying Spagetti Monster would exist, but God would eat it for lunch. Alright, alright come back down to reality now! This escapade proves the point that we should not be too generous. Such bizarre notions of the possible do not respect the elegant universe we can actually observe, and it’s not a multiverse. . . yet. And, if we eventually find we are in a multiverse, it will not necessarily be infinite. How could we even prove that it is infinite?
Barring an infinite multiverse which I think is reasonable, how difficult is it to make earth-like complex life? We will address this in more detail in part 2.