Background: Population

The populations of all living things on earth are naturally regulated by normal restraints:
  • predation of the young & infirm
  • serious mistakes & errors in judgement
  • fights and wars over sex and territory
  • diseases & parasites
  • eventual natural death of old age
Periodic natural events also exact a toll on populations:
  • volcanic activity
  • ensuing droughts and famine
  • hurricanes & storms
  • earthquakes
  • tsunamis, and other such local disasters

In addition to these above, ice ages come and go over thousands of years, gradually reducing populations, which then rebound when the ice retreats. Meteors also occasionally strike, dramatically upsetting the environment, causing larger extinctions.