Trying to understand life solely from the study of living organisms is like trying to understand a 2 hour movie by just watching the last 5 minutes. You may learn the final outcome, but not how or why, and you would miss all the interesting things that have happened along the way. For the truth is, much of the mystery of life is still a mystery, buried in the 3.6-3.8 billion year history of life.

• Life on Earth at this moment is vastly more complex than most of us realize, yet ninety-nine percent, probably more, of the species that have lived on this planet are extinct.
• The most abundant and most important life forms throughout earth history have been bacteria. They invented all the important biochemical pathways, created the first oxygen atmosphere, and are responsible for the most important biogeochemical links.

• Multicellular life has existed on earth for only about 15 percent of its age.
• Yet virtually none of the multicellular phyla have gone extinct.
• While at the same time most of us would find almost nothing familiar about marine life 500 million years ago.

• Without life the Earth today would be without significant water, would have an atmosphere of about 95% carbon dioxide, and an average temperature closer to 200 degrees rather than the present 55 degrees - a thermodynamically closed and dead planet more akin to Mars than the Earth today.
• Yet, in the past 3.5 billion years the earth and life have experienced several environmental crises more severe than anything we consider an environmental crisis today, crises that have reset the evolutionary clock and sent life off in entirely new directions.

The paleontological study of life is not simply about the past it is also about change and continuity. Most of all it is about the long run. Earth environments and life's relationship to those environments cannot be understood in isolation. Environmental conditions that exist today are embedded in and reflect processes that can only be understood at time spans extending far beyond the short window of human experience, far beyond experiments run under controlled laboratory conditions and for time spans that are geologically instantaneous.

The study of paleontology tells us that life processes in a geological context are historical events; their magnitude, structure, cause, and consequences have been highly variable. Furthermore, these variations are patterned in ways we are only beginning to understand, and that cannot be understood only from study of the present. Life can be understood only in terms of the earth system as a whole traced through it 4 billion years of dynamic change.

Finally, unraveling the history of life requires many lines of evidence, biological, geological, paleontological, biochemical, and biogeochemical. This course applies all these lines of evidence to understand not only life itself, but also the scientific controversies that surround our study of it.