Chapter 4: Origin of Life on Earth

IV. Origin of Life on Earth

  1. Reiterate the importance of the concept of scaffolding. "By developing aerobic bioenergetic processes, the prokaryotes produced oxygen which first, for 2,000 million years, was used up in the wxidation of iron and sulphur on the earth's surface but ultimately led to the appearance of free atmospheric oxygen. Since then, the self-organizing 'Gaia' system of biosphere and atmosphere (Margulis and Lovelock, 1974) regulates and stabilizes the conditions for complex life on earth, in particular the appearance of eukaryotic cells and multicellular organisms. In the same way, the development of life gave rise to complex ecosystems which, in turn, led to the development of specialized skills and thereby to societies with division of labor, and so forth." (Jantsch, 1982, 347)
  2. Dawkins' Replicators
  3. Kauffman's autocatalytic sets

    "[There are] good reasons to believe that sufficiently complex mixes of chemicals can spontaneously crystallize into systems with the ability to collectively catalyze the network of chemical reactions by which the molecules themselves are formed. Such collectively autocatalytic sets sustain themselves and reproduce. This is no less than what we call a living metabolism, the tangle of chemical reactions that power every one of our cells. Life, in this view, is an emergent phenomenon arising as the molecular diversity of a prebiotic chemical system increases beyond a threshold of complexity."

    -Stuart Kauffman, from At Home in the Universe


  4. Margulis's theory of symbiotic origin of eukaryotic cells (Margulis, 1970)
  5. Edelman: "A heritable change in morphoregulatory genes followed by natural selection for fitness based on the changed morophology may lead to molecular heterochrony." (1989, 242)
  6. What's happened since, in broad strokes:
    1. Replicators --> Prokaryotes
    2. Prokaryotes --> Eukaryotes (Cambrian explosion?)
    3. Eukaryotes --> Metazoans
    4. Metazoans --> meme-carriers (social organisms w/ sense of self)