Robinson's Podcast 263 - Sara Imari Walker: Astrobiology, Aliens, and the Origin of Life
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Nov 9, 2025 
In this engaging discussion, Sara Imari Walker, a leading astrobiologist and professor at Arizona State University, dives into the physics that underpin life. She explores assembly theory and its implications for defining life, challenging the conventional selfish gene narrative. Sara shares insights on where we might find aliens, the complexity of life's origins, and the intriguing concept of Boltzmann brains. Additionally, she highlights the potential of assembly theory to guide searches for biosignatures, bridging the gap between theoretical physics and astrobiology.
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Disciplines Are Human Categories
- Sara Imari Walker argues disciplines are human categories and the origin-of-life problem sits between biology, chemistry, and physics.
- She frames astrobiology as seeking universal regularities rather than Earth-specific narratives.
Origin Of Life Is A Cascade Of Transitions
- Walker emphasizes the origin of life likely involved multiple molecular major transitions, not a single jump.
- She warns simple replication experiments often simplify molecules and don't recreate complex cellular architecture.
Meeting Lee Cronin Sparked Assembly Work
- Walker describes meeting chemist Lee Cronin and finding his lab's experimental approach matched her theoretical questions.
- Their collaboration led to developing assembly theory and experimental metrology for complexity.
