Paleontology

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How did non-living chemicals become living
creatures?

• What does it mean to be alive?
• Energy from chemical reactions can assist in
  other chemical reactions
• Precursor to eating
• Some chemicals catalyze other chemical reactions
• Precursor to protein synthesis and metabolism?
• Some chemicals are capable of self-replication
• Precursor to reproduction?

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Possible Sites for the Origin of Life

• Clay
• Mineral structure acted as template for organic
  material
• Pyrite
• Mineral structure acted as template for organic
  material
• Bubbles
• separation of chemical environments within and
  without
• Tidal Pools
• separation of chemical environments within and
  without
• Hot springs/Hydrothermal Vents

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A New Hypothesis

• Life may have originated near hot springs and
  volcanic vents
• Heat supplied the energy for life processes
• Energy also available from chemical reactions
• Entire ecosystems without a basis in sunlight!

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Organisms around a modern black smoker vent
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Evidence

• Genetic mapping of living bacteria
• Oldest groups are Thermophiles
• Hot Springs
• Volcanic vents on sea floor
• Fossil evidence has not been found yet
• Such settings are not likely to be preserved in
  the rock record sea floor is subducted!

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Earliest Fossils Prokaryotes

• Prokaryotes cells with no nucleus
• Mostly cyanobacteria (formerly blue-green algae)
• Single cells
• Strings of cells
• Mats of cells Stromatolites
• Structures built as mats trap and bind sediment

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Cyanobacteria 3.46 Ga
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Stromatolites - Modern and Ancient
Saratoga Springs, NY
Shark Bay, Australia
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Extraterrestrial Origins of Life?

• Ingredients in comets
• Evidence from meteorites
• Could life have been transplanted to Earth from
  an extraterrestrial source?
• Did life arise on Earth and other planets
  simultaneously?

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Magnetite from Martian Meteorite evidence of
bacteria?
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The Allan Hills MeteoriteBacteria(?) from Mars
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Life in Stasis 3 Ga of Single Cells

• Life begins approximately 4.0 Ga
• 3.8 Ga first stromatolites
• 3.46 Ga preserved filaments of cyanobacteria
• 1.9-1.7 Ga at least 12 species of prokaryotes
• 1.0 Ga first eukaryotes
• 0.9 Ga (900 Ma) sexual reproduction
• 600 Ma first multicellular organisms

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The Ediacaran BiotaEarliest Multicellular Life