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Chapter Twenty-one — Life Goes On

A Short History of Nearly Everything – by Bill Bryson

Chapter 21 — Life Goes On

  • It isn’t easy to become a fossil.  The fate of nearly all living organisms (over 99.9% of them) is to compost down to nothingness.
  • Only about 1 bone in a billion, it is thought, ever becomes fossilized.  If that is so, it means that the complete fossil legacy of all the Americans alive today (270 million people with 206 bones each), will be about 50 bones (one quarter of a complete skeleton).
  • Fossils are in every sense vanishingly rare.  Most of what has lived on Earth has left behind no record at all.  It has been estimated that less than one species in ten thousand has made it into the fossil record.
  • The Earth has produced 30 billion species of creatures.  There are only 250,000 species represented in the fossil record, for a proportion of just one in 120,000.
  • The fossil record is biased in favor of marine creatures.  About 95% of all the fossils we possess are of animals that once lived under water.
  • The reign of trilobites ran for 300 million years (twice the span of dinosaurs).  Humans have survived for one-half of 1 percent as long as the trilobites.
  • Trilobites had very unusual visual systems.  Their eyes were made of calcite rods, the same stuff that forms limestone.
  • It is almost impossible to appreciate how remote in time the Cambrian outburst was.  If you could fly backwards into the past at the rate of one year per second, it would take you about 30 minutes to reach the time of Christ, a little over three weeks to get back to the beginnings of human life, and over TWENTY YEARS to reach the dawn of the Cambrian period.
  • The distinctions between plant and animal are not always clear even now.  The modern sponge spends its life fixed to a single spot and has no eyes or brain or beating heart, and yet it is an animal.

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