• The age of the Earth is 4.54 Billion years old.
  • This number was determined by radiometric dating terrestrial and lunar samples with additional calibration to meteorites.
  • With this large number of years in mind, there was ample time for historic changes to occur on the planet that encompass geologic, climate and organism population shifts.
  • One major climate changing shift occurred about 4 Billion years ago as atmospheric oxygen began to accumulate due to the first photoautotrophs.
  • Comparing the geologic time scale to a 24-hour clock, modern humans only arrived on this planet at 4 seconds to midnight.