A Brief History of Life

  • By Lexi Krock
  • Posted 02.01.02
  • NOVA

It's hard to wrap your mind around the concept of 4.5 billion years. For many of us, the Pyramids–built 4,500 years ago, a millionth of that time span–symbolize the distant past. The geological time scale helps us grapple with the vast swaths of time that life has existed on Earth, dividing it into eras, periods, and epochs. With our illustrated version, explore 4.5 billion years of life in just a few minutes.

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An overview of the history of life on Earth, from the earliest bacteria to the first modern humans


The Oxford Encyclopedia of Evolution by Mark Pagel, ed. New York: Oxford University Press, 2002.

The Book of Life: An Illustrated History of the Evolution of Life on Earth by Stephen Jay Gould, ed. New York: W.W. Norton, 1993.

Five Kingdoms: An Illustrated Guide to the Phyla of Life on Earth by Lynn Margulis et al. New York: W.H. Freeman, 1998.



(Precambrian, Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Jurassic, Cretaceous)
© John Sibbick
(Permian, Triassic, Quaternary)
© Douglas Henderson
Courtesy Department Library Services, American Museum of Natural History

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  • Fossil Evidence

    Examine five transitional species that fill so-called gaps in the fossil record.

  • History of the Universe

    Explore, in brief, the evolution of the universe—from the Big Bang to the distant future.


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