Start calculating the distance from the end of the sidewalk (present) for each of the geologic eras in Earth's history. Then describe the breakup of Pangaea as a stroll along this geological sidewalk, locating various events in the history of life along the way.

Where along the sidewalk do humans first appear (circa 1.5 million years ago)? How far would you have to extend your sidwalk to reach all the way back to the origin of Earth, circa 4.6 billion years ago?

Example:

• The earliest date we have for land plants and insects is around 430 million years ago.
• 100 meters ÷ 570 million years = 0.175 meters per million years
• 430 million years x 0.175 meters per million years = 75.4 meters.
• Remember, this is the distance from the end of the sidewalk, so 100 meters - 75.4 meters = 24.6 meters from the beginning of the sidewalk.

• Biogeography Fundamentals
• Geography of Species Distributions