Interview, Fireside Chat
Betül Kaçar: Origin of Life, Ancient DNA, Panspermia, and Aliens | Lex Fridman Podcast #350
- Batul Kachar argues that while chemistry, physics, and geology can be studied anywhere in the universe, biology is unique to Earth because it relies on specific historical selection rules that cannot be extrapolated from physical laws alone.
- Phylogenetic trees are constructed by analyzing the diversity of modern life (the "tips") and working backward to reconstruct ancestral lineages, a process used to infer ancient gene sequences and protein functions.
- Kachar's research focuses on the "fun stuff" occurring after the origin of life, specifically the innovations of single-celled organisms, photosynthesis, and the rise of eukaryotes, which are poorly represented in the fossil record.
- The most critical biological innovation discussed is nitrogen fixation, a singularity in evolutionary history where a single enzymatic pathway (nitrogenase) evolved roughly 3 billion years ago to convert atmospheric nitrogen into bioavailable ammonia.
- The translation machinery is described as the central computational device of life, functioning as a chemical, physical, informatic, and biological system that converts linear RNA sequences into functional proteins.
- Unlike modern computers, the translation machinery is a self-contained system that couples information processing directly to physical function and chemical constraints, operating with high energy efficiency despite slow speeds (approx. 21 amino acids per second in bacteria).
- The genetic code utilizes 64 codon states to encode 20 amino acids, creating a degenerate code that provides resilience against errors, allowing mutations to often result in the same amino acid or a chemically similar one.
- The Last Universal Common Ancestor (LUCA) is estimated to have lived between 3.5 and 3.8 billion years ago, representing a population of organisms rather than a single individual, from which all current life descends.
- Experimental evolution studies involving the replacement of modern elongation factors with 700-million-year-old ancestral versions revealed that evolution struggles with multitasking; when one module is broken, the cell often prioritizes fixing immediate symptoms or optimizing other modules rather than restoring the broken translation machinery to its former optimum.
- This "evolutionary stalling" suggests that evolution is a "lazy" process that fixes the most immediate impediments rather than solving global optimality problems, leading to suboptimal states that persist.
- Kachar identifies several "singularities" in evolutionary history—innovations like the origin of life, nitrogen fixation, photosynthesis, and eukaryotes—that occurred only once and fundamentally altered the planet's trajectory.
- Regarding the "tape of life" hypothesis (rewinding and replaying Earth's history), Kachar posits that while life itself is likely inevitable given the right chemistry, the specific outcomes (e.g., complex multicellular life, human-like intelligence) are contingent on rare molecular events and are not guaranteed to repeat.
- Kachar rejects the term "panspermia" for the spread of life, preferring "protospermia," which involves seeding a planet with specific chemical ingredients to enable local evolution rather than introducing pre-formed, Earth-like organisms.
- She argues that the moral justification for seeding other planets should not stem from fear of human extinction but from a desire to propagate the "spark" of chemical evolution and ensure life continues, provided it respects the target planet's existing chemistry.
- Kachar emphasizes that the worst-case scenario of creating life is not the emergence of a super-virus, but the potential creation of conscious beings capable of suffering, which would impose a profound ethical responsibility to alleviate that suffering.
- She contends that suffering is an inherent feature of evolution ("brutal place of desperately trying to survive") and that the capacity to appreciate beauty and meaning is a human choice that exists alongside this harsh reality.
- Kachar highlights that opportunities for scientific inquiry are unevenly distributed globally, citing her experience in Bosnia where a lack of resources did not diminish the brilliance and hope of the local population to engage with science.
- She advises young scientists and individuals to trust their own voices, practice self-respect and love, and understand that the scientific method is a learnable skill rather than a trait reserved for the naturally gifted.
- The conversation concludes with the sentiment that life has no inherent external meaning, but meaning is derived from the human capacity to find beauty in the void and to "leave it as you would want to find it."