Discovery Gallery

Imprints of the Past

The Solar System began to form at least 4.6 billion years ago. The oldest-known life forms were present about 3.5 billion years ago. Many more species have evolved, flourished, and fallen into extinction than are alive today. Modern human beings have existed fewer than 130,000 years--a relative millisecond in the history of the universe. We can learn about the distant past because our planet is like a gigantic book, written slowly over enormous stretches of time. We have begun to uncover the history of life and our own physical origins by "reading" scientific clues. Some of our planet's rocks have preserved fossilized traces of earlier life forms. They record the origin, proliferation, evolution, way of living, and extinction of plant and animal species over millions of years. From fossils as small as pollen grains and larger than Tyrannosaurus rex, paleontologists read our planet's shifting geological history, uncover the beginnings of our own species, and discover the dynamic patterns of change that propel us toward our future.

Shark Teeth

Pteranodon

Allosaurus foot

• Trilobites, Ammonites, and Belemnites
• The Dinosaur's Reign
• Mastodon and Mammoth Teeth
• Suspended in Time

For more information on evolution, fossils, and paleontology, see Earth Sciences at the National Science Foundation.

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