MEPX
Chapter 8 of 10All chapters
  1. 1The mechanism
  2. 2Where variation comes from
  3. 3Selection
  4. 4Chance
  5. 5How species form
  6. 6The evidence
  7. 7Common misunderstandings
  8. 8Deep time
  9. 9Human evolution
  10. 10Why it matters practically

Chapter 8 of 10

Deep time

The scale that makes it work.

How long

Earth is about 4.5 billion years old and life appeared within the first billion. Complex animals arrive only in the last 600 million years, and our species in the last 300,000.

  • Radiometric dating gives independent, cross-checking age estimates.
  • Small changes per generation become large over millions of generations.

Extinction

More than 99 percent of species that ever lived are extinct. Five mass extinctions reshaped life, and each one opened space that the survivors radiated into.