Adam Frank: evaluation

Transcript context

…Because it’s certainly true that we have gone through almost extinction events. We’ve had five mass extinctions. But you don’t necessarily see that there was this giant evolutionary leap happening after those. With the comet impact, the K-T Boundary, certainly lots of niches opened up. That’s why we’re here, because our ancestors were little basically rodents, rats living under the footsteps of the dinosaurs. It was that comet impact that opened the route for us. That still took another 65 million years. It was like this thing immediately happened. But what we found with this Hard Steps Paper, because the whole idea of the Hard Steps Paper was it was one of these anthropic reasoning kinds of things. Where Brandon Carter said, “Oh, look. The intelligence doesn’t show up on Earth until about almost close to when the end of the Sun’s lifetime.” He’s like, “Well, there should be no reason why the Sun’s lifetime and the time for evolution to produce intelligence should be the same.” He goes through all this reasoning, anthropic reasoning. He ends up with the idea that, “Oh, it must be that the odds of getting intelligence are super-low, and so that’s the hard step.” There was a series of steps in evolution that were very, very hard. Because of that, you can calculate some probability distributions. Everybody loves a good probability distribution, and they went a long way with this. But it turns out that the whole thing is flawed because, when you look at it, of course the timescale for the Sun’s evolution and the timescale for the evolution on life are coupled, because the timescale for evolution of the Earth is coupled, is about the same timescale as the evolution of the Sun. It’s billions of years. The Earth evolves over billions of years. Life and the Earth co-evolve. That’s what Brandon Carter didn’t see is that actually, the fate of the Earth the fate of life are inextricably combined. This is really important for astrobiology, too. Life doesn’t happen on a planet, it happens to a planet. This is something that David Grinspoon and Sara Walker both say, and I agree with this. It’s a really nice way of putting it. Plate tectonics, the evolution of oxygen, of an oxygen atmosphere, which only happened because of life. These things, these are things that are happening where life and the planet are sloshing back-and-forth. Rather than, to your point about do you need giant catastrophes, maybe not giant catastrophes. But what happens is, as the Earth and life are evolving together, windows are opening up, evolutionary windows. For example, life put oxygen into the atmosphere. When life invented this new form of photosynthesis about 2.5 billion years ago, that broke water apart to work to do its chemical shenanigans. It broke water apart and pushed oxygen into the atmosphere. That’s why there’s oxygen in the atmosphere. It’s only because of life. ago, that broke water apart to work to do its chemical shenanigans. It broke water apart and pushed oxygen into the atmosphere. That’s why there’s oxygen in the atmosphere. It’s only because of life. That opened up huge possibilities, new spaces for evolution to happen. But it also changed the chemistry of the planet forever. The introduction of oxygen photosynthesis changed the planet forever, and it opened up a bunch of windows for evolution that wouldn’t have happened otherwise. Like for example, you and I, we need that amount of oxygen. Big-brained creatures need an oxygen-rich atmosphere because oxygen is so potent for metabolism. You couldn’t get intelligent creatures 100 million years after the planet formed. So really, on a scale of a planet when there’s billions and trillions of organisms on a planet, they can actually have planetary scale impact.…

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