• How old is this planet anyway?
  • Theories of Origin
  • Geological and Biological 
   timescales
  • Phylogeny
   How old is this planet anyway?
    –The Universe is probably ~13 billion years 
     old (Big Bang Theory/Doppler Shift)
    –Earth is ~4.5 billion years old (begins with 
     cooling of crust/solidification)
    –Earliest records of life ~3.5 billion years ago
    –First humans (Australopithecus), 0.005 
     billion years ago
    –Discovery of Australopithecus fossils , 
     0.0000000002 billion years ago
   The Fragility of Life - Coincidence #1
                                 • Life can only exist 
                                   within temperatures 
                                   corresponding to the 
                                   boiling and freezing 
                                   point of water
                                 • This range is a 
                                   fraction of the range 
                                   between absolute 
                                   zero (-273°C) and 
                                   the temperature of 
                                              6
                                   the sun (10 °C)
        How did life evolve?
   • Three theories
     –Creationism
     –Extraterrestrial origin (Panspermia)
     –Spontaneous Origin (Coincidence #2)
      • Black smokers?
   Physical conditions of early Earth 
       - Coincidence #3
  • Temperatures in correct range (in 
   general, water in fluid state, carbon 
   compounds non-brittle)
  • Size of planet retains an atmosphere
  • Early atmosphere lacked oxygen, 
   therefore highly reductive
  • High energy bombardment from sun
  promotes generation of organics