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After "Project Hail Mary" (strong recommend) I am now into binging for the purpose of review (and fun!) Apple's "For All Mankind". On that theme: something from the archives. "Are we alone?" Most know the arguments for alien intelligence. Here is an argument against it that you may not have heard before: "And here's Slezak's argument. I love it, to tell you the truth, because it's a criticism - I don't believe it - it's a criticism - of that argument that I began the entire episode with. That argument about astronomical numbers. 10 to the power of 25 planets. 10, or sorry, a 1 followed by 25 zeros. That's the number of planets in the universe. That's phenomenal - an astronomical number! Well, here's the number that's going to blow that out of the water. Absolutely blow that out of the water. Make that number appear as a pittance, a tiny number by comparison. Here's how we do it. Here's the thought experiment. Imagine that you're a human being and you're looking back at all the steps in evolutionary terms that have led to the human being. How many would there be? We all started, all species that exist on Earth now, started from that first single-celled life form, that bacteria or archaea, that very microscopic thing, single-celled, that existed billions of years ago. And which for billions of years didn't change, by the way, so far as we can tell. How many steps are there between evolutionary steps, discrete evolutionary changes in the DNA from that first bacteria, single-celled thing, to human beings? This single celled it's evolving from the single celled thing into the multicellular thing into some sort of fish thing. You've seen the pictures, you know, and then it becomes like a fish thing that's got legs, like some sort of amphibian, the amphibian thing becomes like a reptile sort of thing, and the reptile becomes a rat, and then the rat thing becomes like a monkey thing, which becomes more upright, and eventually you get to a human. This occurs over billions of years, billions of years this takes. How many discrete steps is there? Millions? Thousands? Okay, let's be really, really, really conservative. Let's say, and this is obviously fantasy talk, but let's say there's only 100. Let's say there's only 100 such steps. Completely unrealistic. There's way more than that, but for the purpose of my argument, I want to make the number as small as possible. Because I said I'm going to generate a really big number here, so I'm going to present you the smallest possible big number. Let's say there's only 100. Now, each of those steps that led to us, that necessarily led to us. Each of those steps that led to us, that didn't have to lead to us, but led to us. Necessarily was required in order to lead to us, but we can get back to that. What chance does any one of those steps have of occurring? It could have occurred or not. You know, the lizard thing didn't have to turn into the rat thing. Well, the fish didn't have to turn into the fish with legs that could survive in an atmosphere rather than in...the ocean. Maybe each of those steps has like a one in a million chance of happening? Maybe one in a thousand chance? Let's be conservative. Let's be really generous. Let's say any of those steps had a one in 10 chance of happening. It's pretty high probability. Now, what we have is this situation. Let's say we've got those hundred steps and each of those hundred steps has a one in 10 chance of occurring. Well, that means that for any two of them in a row, that would be one in 10 times one in 10 chance of occurring, and one in 100 chance of occurring for both of them to happen consecutively in just the right order to lead to a human being. The only species that we know of on the face of the planet that has the capacity for creative thought or leading to the common ancestor that we had with other intelligent species that existed on the planet. There was this first universal explainer this first creatively thinking human being. Let's say there's a hundred steps. Each of those steps has a one in ten chance of occurring. Then what we have, the mathematics works out like this. It's one in ten times one in ten times one in ten. It's one in ten times one in ten a hundred times. Or one in ten to the power of a hundred. Now, you don't have to know much maths to know that this is one over ten to the power of hundred. One over one followed by a hundred and one zeros. 101 zeros! Now we can see this number completely destroys that 10 to the power of 25. So anyone who's talking about the astronomically large number of planets that's out there and the astronomically large number of places that life could be, if we seeded every single one of those planets, every single one of them with bacteria, like we were seeded with, for want of another word, a few billion years ago here on Earth. And even if we made every single one of those planets, really friendly, bio-friendly, gave it the right conditions, lots of oxygen, lots of water, oceans, wind, lightning, sun, of just the right temperature. Even if we made all the planets like that, there would be no chance if this sequence of events was unique, if this sequence of events was unique, that it should be replicated out there anywhere at all. Now, many people might say, and this is a reasonable criticism of this, is that there could be various ways, various evolutionary paths that could lead to a human being. But again, that raises the question of convergent evolution. If there were these multiple ways of arriving at intelligent, creative, thinking people, then we should have seen other examples of that arise independently here on Earth. But again, how long would we have to have waited in Australia for it to have evolved people? The most complicated creatures that existed here in Australia five million years ago were kangaroos and some wombats. Possums. If we left them isolated as an experiment for another million, 10 million, 100 million, billion years, does anyone expect that those creatures will evolve into something creative, intelligent, and able to send radio signals and perhaps travel across the galaxy? There's no reason to think that. There's no reason to think that because evolution doesn't work that way. That if the conditions are right, those creatures will just remain the same. You need selection pressure for evolution to really to cause diversity and to take advantage of variation. And of course, that can happen around the universe. But there's no reason to presume that there is this intelligence niche. And what Lineweaver calls this is the "planet of the apes hypothesis" - the planet of the apes hypothesis - that when you take away the human beings out of the situation, that there is this niche left behind, there's this place for animals to evolve into because there's nothing filling that particular niche. And so the kangaroos will actually evolve into people because in the planet of the apes, the premise of the movie is the human beings are wiped out for whatever reason. And years later, it is discovered by is it time travelers? I can't remember. Are the human beings from the future or something? Anyway, the apes, the great apes, the chimpanzees, the orangutans, they evolve into people. They become fully functioning, creative people that have technology and civilization just like human beings do. In other words, there is an arrow to evolution that Darwinian blind evolution will take a great ape and turn it into a person left long enough, if left long enough. This is just a misconception. It's a misconception about how evolution works. so Lineweaver's point is, and so is Slezak's point, that an answer to the Fermi paradox is we're utterly alone. The mathematics on the one hand doesn't make any sense. There simply aren't enough planets. The universe isn't big enough to ensure that evolution is going to lead to complicated life forms because it only happened here on earth once. There have been countless millions of species, 99.9 % of which have gone completely extinct. None of which showed any sign of creative intelligence like us, except for our common ancestor, okay, and those other species that we evolved from."