Image Credits: Proto solar nebula: Spitzer Space Telescope
13.7     billion years - Formation of hydrogen and helium in Big Bang
          4.9     billion years - Oldest meteorite forms
          4.58  billion years - Most consistent age for formation of sun
          4.54  billion years - Age of Earth
          4.4     billion years - Sun begins life only 70% current brightness
          3.5     billion years - Earth day is 15 hours long
          3.0     billion years - Oldest record of Earth's magnetic field
          3.0     billion years - Sun grows in brightness to 80% of current level.
          2.0     billion years - Solar luminosity is now 85% of current level.
        
        900     million years - Length of day is now 18 hours long.
        750     million years - Large ice packs cover earth nearly to equator
        543     million years - Cambrian Explosion of complex organisms.
        500     million years - Solar luminosity only 6% less than today.
        320     million years - First ancestors to mammals appear
        300     million years - Solar luminosity only 3% less than today.
        250     million years - Permian Mass extinction
        100     million years - Earth's magnetic field 3x stronger than today
          65     million years - Cretaceous Dinosaur Extinction
          60     million years - Primitive primates appear
          55     million years - Major global warming episode
          27     million years - Primitive apes emerge
            6     million years - Great Apes and Hominids 'split' genetically
            2     million years - Tool-making humanoid ancestors emerge
        
        750     thousand years - End of last magnetic reversal
        500     thousand years - First evidence of fire usage
        400     thousand years - First use of paint by human ancestors
        150     thousand years - Neanderthal's appear
        130     thousand years - Beginning of Eemian Interglacial age
        100     thousand years - Modern humans appear
          50     thousand years - Major change in human behavior, art, tools
          45     thousand years - Largest animals disappear from human habitats
          28     thousand years - Neanderthal's disappear
          25     thousand years - Elaborate burial customs appear
          20     thousand years - Start of last Ice Age
          17     thousand years - Oldest star map created on cave wall
          12     thousand years - Ice Age ends. Earth grows warmer
          10     thousand years - Humans colonize North America
        
The Origin of the Cosmos, Earth, Sun, and Humans