Sara Walker: The Origin of Life on Earth and Alien Worlds | Lex Fridman Podcast #198

The following is a conversation with Sara Walker, an astrobiologist and theoretical physicist at Arizona State University and the Santa Fe Institute. She's interested in the origin of life, how to find life on other worlds, and in general, the more fundamental question of what even life is. She seeks to discover the universal laws that describe living systems on Earth and elsewhere using physics, biology, and computation. Quick mention of our sponsors: Athletic Greens, NetSuite, Blinkist, and Magic Spoon. Check them out in the description to support this podcast. As a side note, let me say that my hope for this podcast is to try and alternate between technical and non-technical discussions, to jump from the big picture down to specific detailed research, and back to the big picture, and to do so with scientists and non-scientists. Long-term, I hope to alternate between discussions of cutting edge research in AI, physics, biology, to topics of music, sport, and history, and then back to AI. AI is home. I hope you come along with me for that, uh, wild oscillating journey. Some people message me saying to slow down since they're falling behind on the episodes of this podcast. To their disappointment, I have to say that I'll probably do more episodes, not less, but you really don't need to listen to every episode. Just listen to the ones that spark your curiosity. Think about it like a party full of strangers. You don't have to talk to everyone. Just walk over to the ones who look interesting and get to know them. And if you're lucky, that one conversation with a stranger might change the direction of your life. And it's a short life, so be picky with the strangers you talk to at this metaphorical party. This is the Lex Fridman Podcast, and here is my conversation with Sara Walker. How did life originate on Earth? What are the various hypotheses for how life originated on Earth?

Yeah, so I guess you're asking a historical question, which is always a good s- place to start thinking about life. Um, so there's a lot of ideas about how life started on Earth. Um, probably the most popular is what's called the RNA world scenario. Um, so this idea is probably the one that you'll see most reported in the news, um, and is based on the idea that there are, um, molecules in our bodies, um, that, uh, relay genetic information, and we know those as DNA obviously, but there's also sort of an intermediary called RNA, ribonucleic acid, um, that also plays the role of proteins. And, um, people came up with this idea in the '80s that maybe that was the first genetic material because it could play both roles of being genetic and performing catalysis. And then somehow that idea got reduced to this idea that there was a molecule that emerged on early Earth and underwent Darwinian evolution, and that was the start of life. Um, so there's a lot of assumptions, um, packed in there that we could unpack, um, but that's sort of the leading hypothesis. There's also other ideas about life starting as metabolism, and so that's more connected to the geochemistry of early Earth-