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

Episode Summary

Executive Summary: Batu Kachar explains how studying ancient genes, translation machinery, and evolutionary trees can reveal life’s deep history and its core features: chemistry, information processing, resilience, and memory. The conversation ranges from nitrogen fixation and the genetic code to experimental evolution, origin-of-life research, astrobiology, and the ethics of seeding life elsewhere.

Main Topics: The tree of life and reconstructing ancient biology (Priority: 5/5): Kachar describes phylogenetic trees as a way to reverse-engineer life’s history from present-day organisms, genes, proteins, and species, allowing scientists to infer ancient ancestors and evolutionary events. Translation as life’s core information-processing machine (Priority: 5/5): A major focus is the translation machinery, which converts mRNA into proteins. Kachar argues it is the oldest computational device in life and uniquely combines chemistry, physics, information, computation, and biology. Nitrogen fixation and essential biochemical innovations (Priority: 4/5): The discussion covers why nitrogen fixation is essential for life, how it evolved once (or near once) on Earth, and why it was a foundational innovation enabling complex life. Experimental evolution and evolutionary stalling (Priority: 5/5): Kachar explains lab evolution experiments where ancient or divergent proteins were inserted into bacteria to study how cells respond to perturbations and why evolution often improves one module at a time rather than multitasking across many. Origin of life and the search for self-organizing chemistry (Priority: 5/5): They discuss prebiotic chemistry, Miller-Urey-style experiments, RNA-world ideas, and what would count as compelling evidence of life-like emergence in a flask or simulation. Astrobiology, panspermia, and life beyond Earth (Priority: 4/5): The conversation weighs whether life is common in the universe, whether only microbes may be widespread, and whether future missions should merely search for life or help seed conditions for it. Meaning, suffering, humility, and scientific optimism (Priority: 4/5): The interview closes on philosophy and ethics: the role of suffering, the importance of optimism in science, and the responsibility to protect life on Earth and elsewhere.

Key Arguments: Present-day organisms are the tips of the tree of life; by comparing them, scientists can infer ancient ancestry and reconstruct lost biology. Translation is not merely metabolism; it is a tightly coupled informational, chemical, computational, and biological system that may be central to life’s origin. The genetic code’s structure is highly robust and redundant, with 64 codons mapping onto 20 amino acids and built-in resilience to errors. Nitrogen fixation is essential to life as we know it and appears to have evolved only once in nature, making it a singular, foundational innovation. Evolution often fixes the most immediate bottleneck rather than optimizing every module at once; in Kachar’s experiments, cells responded locally to perturbation. Ancient versions of essential proteins can be inserted into modern bacteria to probe what changes are tolerated and how selection restores function. Origin-of-life research is moving from simple building blocks toward systems-level chemistry that can self-organize, remember, and respond. Astrobiology should not focus only on Earth-like colonization; a better goal may be understanding a planet’s chemistry and whether it can support a chemical revolution of its own. Scientific progress requires optimism, patience, and a willingness to be wrong; boredom is a useful signal that a question may not be worth pursuing. Humans are not separate from life’s deep history; we are the product of billions of years of chemical and biological evolution. Data Points: Age of life’s root / LUCA: ~3.8 billion years ago - Kachar says 3.5 billion years is too conservative and that 3.8 billion is safer for the last universal common ancestor. Estimated lifespan: 70–80 years - Used in the sponsor-ad aside to estimate hours in a human life. Hours in a lifetime: ~600,000–700,000 hours - Estimated from a 70–80 year lifespan. E. coli generation time: ~20 minutes - Discussed during the experimental evolution section. Translation rate in bacteria: ~21 amino acids/second - Kachar notes bacterial translation is around 21 amino acids per second. Translation rate in eukaryotes: ~8–9 amino acids/second - Compared with bacterial translation speed. Codons in the genetic code: 64 possible states - Four nucleotide letters in triplets create 64 codons. Standard amino acids encoded: 20 amino acids - Life uses 20 amino acids despite 64 codons. Stop codons: 2–3 stop signals - Kachar notes three stop codons in the standard table. Evolutionary identity in modern elongation factors: ~70% conserved identity - Compared across modern versions of elongation machinery. Identity in resurrected ancestral elongation factors: ~40% conserved identity - When going back in time to ancestral proteins. Experimental evolution duration: 150 days - Bacteria were propagated daily under selection for about 150 days. Mutational response in evolved cells: 4 mutations accumulated - Kachar mentions the system still remained suboptimal and had accumulated four mutations in one analysis. Paper cited on computational efficiency: 2013 - A paper by Zirnov (first author as recalled) on energy use and computational systems. Nitrogen fixation evolution: ~2.7–3.0 billion years ago - Kachar says nitrogen fixation likely evolved around this time.

Pivotal Quotes: "“I think phylogenetic trees could be one of the most romantic and beautiful notions that can come out of biology.”" — Batul Kachar: On why evolutionary trees are central to understanding life’s connectedness and history. "“The entire cell is hopelessly addicted to this main informatic computing, biological, chemical system that is operating at the heart of the cell.”" — Batul Kachar: Describing translation as the cell’s core machine. "“If we are alone, that is quite fascinating, and we definitely have a responsibility to guard what we got better and protect it better and don’t take it for granted.”" — Batul Kachar: On the implications of life in the universe and responsibility toward Earth.

Implications: The episode frames life as an information-processing chemistry that can be probed, partially reconstructed, and perhaps recreated. For science and astrobiology, it argues for systems-level origin-of-life work, careful planetary ethics, and humility about how much remains unknown.