October 25th, 2022

Big Bang to Humankind

3 Origin of Life Hypotheses

Primordial Soup

  • In a hot aqueous environment, we had everything we needed for life.
    • Electrical activity as well.
  • Miller-Urey Experiment (1953)
    • “Recreated” early Earth environment
    • Replicated heat and lightning
    • Condensed mixture and found amino acids, precursors for nucleo bases, etc
  • These results were not replicable
  • The “pre-life conditions” were not accurate
    • Atmosphere could not have held on to hydrogen
    • Methane was not there, it mostly comes from life

Meteorite Hypothesis

  • Meteorites bombard Earth, materials landed on Earth that way.

Interstellar Clouds

  • Miller-Urey did actually recreate interstellar clouds, showing that interstellar clouds can create biological molecules.
  • Meteorites could get biological molecules from interstellar clouds

The Combination Hypothesis

  • Key compounds created in interstellar clouds → meteorites → rain down on Earth → Earth’s conditions allowed it to progress into larger organic molecules


  • Thalidomide was a drug given to pregnant women to help with morning sickness. The half of the drug with inaccessible chirality caused problems with fetal limb development.

Key unanswered questions by origin of life hypotheses

  • How does DNA and RNA self-replicate?
  • How do we make a full nucleic acid?
    • We’ve got the parts, but not how they get put together.
  • Humans are homochiral (only have one chirality) and no theory for the origin of life fully accounts for homochirality.
    • Last common ancestor had homochirality.