Kaçar, Betül

astrobiologist, University of Wisconsin, studying the origin and early evolution of life

Betül Kaçar: Origin of Life, Ancient DNA, Panspermia, and Aliens

Lex Fridman Podcast · Dec 29, 2022

• Betül Kaçar
• origin of life
• translation machinery
• ancient gene resurrection
• phylogenetic trees
• LUCA
• evolutionary stalling
• panspermia and protospermia
• genetic code
• astrobiology

Core ideas

Kaçar explains phylogenetic trees as reconstructions built backward from the "tips" (organisms alive today) toward inferred common ancestors, and describes her lab's central technique — resurrecting ancient genes computationally and inserting them into modern bacteria to create "ancient-modern hybrid" organisms — as a way to study deep evolutionary history that is fundamentally different from Jurassic Park, since researchers work with existing organisms rather than reconstituting extinct ones wholesale. She frames the translation machinery (the cellular system that converts RNA sequences into folded proteins) as arguably the most fundamental and fascinating subsystem of life, describing it through five simultaneous lenses — chemical, physical, informatic, computational, and biological — and arguing that this tight coupling of information to function has no real analog in human-made computers. She walks through the genetic code (four nucleotide letters read in triplets, yielding 64 possible codon states that map onto only 20 amino acids, with built-in redundancy that lets errors occur without breaking the encoded message) as evidence of a highly optimized, universally conserved system that likely required a great deal of chemical evolution before the "Last Universal Common Ancestor" (LUCA) — which she describes as more likely a population of organisms than a single individual, while affirming the broader claim that all known life shares common ancestry.

She discusses her own experimental work on "evolutionary stalling": deliberately disrupting the translation machinery's elongation step in bacteria (by swapping in ancestral or distantly related versions of the elongation protein) and then evolving the resulting impaired bacteria in the lab for 150 days to observe how they adapt. The key finding was that cells facing a disrupted core process tend to fix or optimize one affected module at a time rather than working on multiple problems simultaneously — often settling for a suboptimal fix in the disrupted system while a different, unrelated module improves instead — which she uses to argue evolution is comparatively "lazy," addressing whatever problem is most immediately pressing rather than pursuing a global optimum. She notes translation is remarkably conserved (roughly 60-70% shared identity even across billions of years) and essential to all cellular life, and connects this to a broader point about metabolism (dynamic and flexible, but not focused on rapid repetition) versus computation (repetitive, but not dynamic) — arguing translation is unusual and foundational to biology precisely because it combines both properties.

On the origin of life, Kaçar identifies what she considers a handful of singular, once-only evolutionary "innovations" across roughly 3.8 billion years — the emergence of translation itself, cyanobacteria-driven photosynthesis, eukaryotic endosymbiosis, and the rise of multicellularity/plants among them — contrasted with the much faster, continuous pace of molecular-level mutation and selection. She resists offering a single definition of "life," suggesting instead that it may be best understood as chemistry that explores possible solutions and, crucially, retains a "memory" of successful ones over vast timescales, and states her belief that the origin-of-life research community is close to being able to demonstrate a self-organizing chemical system with the necessary five properties (chemical, physical, informatic, computational, biological) in a laboratory setting within the coming decade — analogous in ambition to the 1950s Miller-Urey experiment that first synthesized amino acids from simulated early-Earth conditions.

The conversation explores speculative territory around astrobiology and cosmic responsibility: Kaçar proposes what she calls "protospermia" (distinct from panspermia) — the idea that humanity might one day identify planets whose existing chemistry is nearly, but not quite, sufficient to spark its own chemical "revolution" toward life, and deliberately supply the missing chemical ingredients already native to that environment, rather than seeding it with Earth life or terraforming it. She's explicit this is not colonization but rather "empowering" a planet's own chemistry, and engages directly with Lex's counter-argument (that if life is likely to entail suffering, seeding new life carries an ethical burden) by arguing that suffering is not a linear, avoidable property of life as we know it, while stressing her own optimism as, in her view, a near-precondition for doing ambitious scientific work at all. She expresses skepticism toward panspermia (life arriving from elsewhere) not on physical grounds but because it relocates the origin-of-life question outside what can be studied experimentally on Earth, while agreeing that even if Earth's earliest chemical ingredients came from elsewhere, the subsequent evolutionary "leaps" (eukaryotes, multicellularity) still happened here and remain scientifically tractable.

She reflects on Stephen Jay Gould's "replaying the tape of life" thought experiment, noting that most versions of it implicitly hold environmental and geological timing constant, whereas she considers the randomness and sequencing of geological events (not just chemistry) to be an underexplored variable in how differently evolution might unfold on a rerun. She closes with reflections on her own background — born and raised in Istanbul before emigrating to the U.S., citing a Turkish saying about never eating in front of a hungry neighbor as emblematic of a cultural emphasis on human connection she has carried with her — and on mentorship, describing a public talk in a war-affected part of Bosnia as a formative reminder that scientific opportunity, unlike raw talent, is unevenly distributed across the world. Asked about meaning, she declines to claim life has an inherent purpose, out of what she frames as respect for those who suffer, but affirms that beauty, love, and the capacity to appreciate existence are themselves worth cultivating regardless — summarized, only half-jokingly, by a sign she recalls from Turkish public restrooms: "leave it as you would want to find it."

Excerpts