We know now that the earth is much, much older than people in Darwin's day thought it to be. Current evolutionary thinkers refer to the enormous time span of earth's geological history as "deep time," and we can only fully understand evolution in this context.

Explore the history of life in the Deep Time Web activity.

Deep Time
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Transformations

How does fossil evidence demonstrate that species have changed over time?

What are some of the major transformations in the evolution of life?

What kinds of fossils would you expect to find in the Cambrian strata of rocks such as the Burgess Shale?

What could account for the Cambrian explosion?

Why is it difficult to demonstrate the slow change of one species into another using the fossil record?

What kinds of fossils are more likely to show transitions between species and groups? Why?

What fossil examples of this transition have been discovered?

Extinction

When did mass extinctions occur, and what organisms were affected?

What is the significance of extinction for the evolution of existing organisms?

Geology

How did the continents change from the Precambrian to the Permian to the Jurassic to the Eocene?

How could the shifting of continents have influenced the distribution and migration of plants and animals?

For more information on extinction, see the BBC Evolution Web site.