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[@DwarkeshPatel] Nick Lane – Life as we know it is chemically inevitable

· 10 min read
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@DwarkeshPatel - "Nick Lane – Life as we know it is chemically inevitable"

Link: https://youtu.be/0GMWxuYuxJI

Short Summary​

This YouTube video features a discussion with evolutionary biochemist Nick Lane, focusing on his energy-centric view of life's origins and evolution. He highlights the unique role of eukaryotes and mitochondria in enabling complex life, arguing that similar geochemical conditions on other planets might lead to the inevitable emergence of life with analogous metabolic processes, though complex life like eukaryotes might be a much rarer occurrence.

Key Quotes​

Here are five direct quotes from the transcript that represent valuable insights, data points, or surprising statements:

  1. "The one thing you could conclude from that is bacteria and archaea, in terms of their genetic repertoire, they’ve actually got a lot more genes, a lot more versatility than eukaryotes do. It’s just that a single bacterial cell has much less in it. But there’s so many different types of bacterial cells that overall they’ve explored genetic sequence space. They had 4 billion years to have a go at that and they never came up with a trick which says it’s not in the genes, it’s not about information. There’s something else which is controlling it. That something is the acquisition of these power packs in our cells called mitochondria." - This quote highlights the surprising genetic diversity of prokaryotes compared to eukaryotes, and emphasizes the critical role of mitochondria in the evolution of complex life.

  2. "If you shrank yourself down to the size of a molecule and stood next to that membrane, you would experience 30 million volts per meter, which is equivalent to a bolt of lightning." - This provides a vivid illustration of the immense electrical force generated across the mitochondrial membrane, crucial for energy production.

  3. "We know that there are, from discoveries of exoplanets in recent years, if you extrapolate how many we’ve not seen yet, the number of wet rocky planets or moons in, say, the Milky Way is probably in the order of 20, 30, 40 billion of them." - This quote delivers an amazing number that underscores the potential abundance of habitable planets.

  4. "If you just had to pull a number out of nowhere and just say, 'This fraction has nucleotides,' what fraction would you say? I would say a substantial fraction. Like over 1%? Yes. I would imagine 50% or something. Really?" - This is a truly astonishing estimate.

  5. "There’s a lovely phrase from James Crow, who’s a geneticist: 'there’s no greater genetic health hazard in the population than fertile old men.'" - This quote about the difference in sperm and egg production is insightful and memorable.

Detailed Summary​

Here is a detailed summary of the YouTube video transcript, broken down into bullet points:

I. Introduction & Eukaryotes' Significance

  • Nick Lane, an evolutionary biochemist, discusses his work on energy flow in the context of life's 4 billion-year history, covering topics from the origin of life to the contingencies in how life works.
  • Key question: Why are eukaryotes so significant in understanding the nature of life?
  • Eukaryotes are the cells that compose complex life forms (plants, animals, fungi, algae, etc.). They are characterized by a nucleus containing DNA and other complex cellular machinery.
  • Eukaryotic cells share similar internal structures across diverse organisms, indicating a single origin event approximately 2 billion years ago.
  • Bacteria and archaea have more genetic versatility than eukaryotes, yet they never achieved the complexity of eukaryotic cells.
  • Key argument: The acquisition of mitochondria (power packs within cells) is crucial to the evolution of eukaryotic complexity.

II. Origin of Life & Hydrothermal Vents

  • Lane explains his research journey, which started with mitochondria, led to the evolution of eukaryotes, and ultimately to the origin of life.
  • Mitochondria's primary function is respiration (energy production) by generating an electrical charge across the membrane.
  • The membrane charge is incredibly strong due to its thinness.
  • This energy-generating system appears universally conserved, suggesting it originated very early in life's history.
  • Key argument: The origin of these energy-generating systems can be traced back to deep-sea hydrothermal vents, specifically alkaline vents, with mineralized pores that provide cell-like structures.
  • The acidic ocean environment and alkaline fluids within the vent create a proton gradient across the mineral pores.
  • These pores contain metals (iron sulfide, nickel sulfides, etc.) that act as catalysts.
  • Autotrophic bacteria use these metals to catalyze the reaction between CO2 and hydrogen (bubbling out of the vent) to create the building blocks of life.
  • The proton gradient across the membrane powers this reaction.
  • The idea is a geological environment provides continuity to the structure of cells as we know them. The bacteria have a charge on their membrane because it was there in hydrothermal vents from the beginning.
  • An endosymbiosis that gives rise to eukaryotes would free you from the constraints of generating charge on the membrane.

III. Implications for Astrobiology

  • Considering the puzzle about why eukaryotes are special and the origin of life can also include planetary systems.
  • The initial research of the origin of life has led to the fundamental forces that will give rise to life and how that could constrain life.
  • What are the chances of seeing the same things on other planets?
  • The discussion shifts to astrobiology: what forces give rise to life, how they constrain it, and whether similar processes might occur on other planets.
  • These processes will constrain life to a similar origin.

IV. Concentration & Catalysts

  • Pores in alkaline vents concentrate organics, preventing them from diffusing into a primordial soup.
  • This concentration provides the environment for the chemiosmotic gradient of protons to catalyze the reaction of hydrogen gas and carbon dioxide to make organics.

V. Chemical Building Blocks

  • Reacting hydrogen and CO2 create Krebs cycle intermediates (carboxylic acids), which are the basic building blocks.
  • These can form amino acids, sugars, and nucleotides.
  • Fatty acids spontaneously form membranes (bilayers).
  • These vesicles can form at high temperatures in the presence of ions.
  • Every life form is continuous with spontaneous chemical reactions.
  • Cells are effectively reduced inside and oxidized outside, mimicking Earth's structure.

VI. Contingency and Determinism

  • What parts of life are contingent, and what parts would be shared even on other planets?
  • Carbon is the obvious candidate to build life on.
  • Proton gradients: could other chemiosmotic gradients be used to drive work? (potentially sodium)
  • Water is everywhere so the same chemistry will keep occurring everywhere.
  • Carbon is very good at the chemistry that it does. It is good at forming strong bonds, so the chemistry of making Lego-type buildings of life.
  • The laws of the universe favor the formation of the chemistry of life.
  • The fundamental bottleneck is eukaryotes.
  • Wet, rocky planets (or moons) will inevitably produce hydrothermal vents because of the chemistry of olivine reacting with water.
  • There are around 20-40 billion wet, rocky planets/moons in the Milky Way.
  • Many of these planets would have the same metabolism due to thermodynamically favored chemistry involving CO2 and hydrogen.
  • Even in other chemistries, similar molecules may arise.
  • According to this story, pretty sophisticated organics are extremely abundant throughout the universe.
  • It is not necessarily collected in an ocean.
  • These vents provide a continuous throughflow, so vent systems have high concentrations of certain materials in pockets.
  • Early prokaryotes then change the composition of the Earth.

VII. Bottlenecks and Eukaryote Evolution

  • Eukaryotes are considered the fundamental bottleneck. Going from early life to prokaryotes changing the composition of Earth is easy.
  • There has to be an advancement from RNA and DNA, ribosomes, and other molecular machines after nucelotides are created.
  • Ribosomes, DNA, and RNA will be made in a significant fraction of habitable planets.
  • There are multiple reasons that it is hard to have an endosymbiotic event like eukaryotic origin.
  • Prokaryotes are pretty small and having another cell inside of you is hard.
  • Many endosymbionts are lost.
  • Prokaryotes can grow faster without an endosymbiont.
  • 1/trillions of endosymbiotic events were successful.
  • Asgard archaea are relatively eukaryotic-like but not complex.
  • Plant, animal, and fungal cells have the same materials. It is adaptation to an internal selection pressure of a battle of the host cell versus endosymbiont.
  • There is a battle between the host cell and the endosymbiont where genetic parasites coming from mitochondria force action to protect one's genome.
  • If this story is true, there is life everywhere.
  • Multicellular organisms are a restriction of chances for all the cells to have a fight.
  • Complex functions require a large genome. The only way to have a large genome is to have mitochondria and a eukaryotic cell.
  • You just want a smaller copy of the genome at the site of respiration.

VIII. Polyploidy

  • Evolution is cleverer than we are. However, evolution has repeated the process of large bacteria with extreme polyploidy with multiple copies of their genome.
  • A symbiosis will do it.
  • All examples of very large bacteria have extreme polyploidy.
  • Not enough genetic space.
  • Small copy of the genome is relevant to respiration.
  • Orgel's second rule: Evolution is more clever than you. There is a probability that carbon is the most common building block, so wet and rocky planets are going to have these same serpentinizing reactions.

IX. Future Directions

  • Observation is crucial to our current understanding of what is out there.
  • Experiments in an anaerobic environment with hydrogen and CO2 are slow, but they can teach about the biochemistry of the origin of life.
  • Work on anesthetics and mitochondria: anesthetics affect mitochondria. It is beginning to imply that an amoeba has consciousness.
  • Feelings may be linked to life. Natural selection acts on feelings as they have physical properties.
  • Bacterial cells need to decide what to do, so how do they measure their environment? Metabolic state in relation to the outside world.
  • Anesthetics may interfere with the fields that mitochondria generate that indicate a metabolic state.

X. Sex

  • Female sex passes on the mitochondria.
  • Sex increases the variance in the nuclear genome and eliminates genes that do not work.
  • Sex increases variance of mitochondrial genes.
  • Mitochondria are being compensated by clean copies to prevent degradation over time.
  • Increasing visibility to selection.
  • Uniparental inheritance is taking the mitochondria from one parent, so you're taking a subset to increase variance between the daughter cells.
  • Two sexes exist because it is the minimization of error with the added benefit that there is an evolutionary niche for only one parent to pass on mitochondria.
  • Males do not really have a germline because they mass-produce sperm.
  • Growth rate and the Y chromosome. Males may grow fast due to lack of constraint in trashing mitochondria as they are not passed down.
  • Is this why women live longer?
  • The Y chromosome would fade away over time, leaving only one gene. It is a matter of how many genes you can maintain in a good state.
  • With regards to bacteria, a large metagenome leads to strains of E. coli living in different environments. The strains can borrow from each other.
  • Eukaryotes had to find a more systematic approach to inherit quality genes across larger genomes.

XI. The Experiment

  • For the origin of life, research should be done in a deep-sea hydrothermal system in an anaerobic environment.

This bullet-point summary captures the core topics, arguments, and information presented in the YouTube video transcript, providing a structured overview of the discussion.