Did life originate somewhere on Earth billions of years ago -- or could it have arrived here on a meteor or a comet from the depths of outer space?

How did we learn that the continents have been moving away from each other in an inexorable dance propelled by mammoth forces beneath the surface of the Earth?

Could a human skull jerry-rigged with an orangutan jaw fool scientists into thinking they held the missing link between apes and man? Is it possible that something as complex and miraculous as the human mind could develop through as "mindless" a process as evolution?

"Origins" (premieres Thursday, January 15, 1998, 8pm ET), the final episode in PBS's five-part A Science Odyssey, takes an epic journey from the Earth's creation to the beginnings of life to the emergence of humankind. From the Arctic tundra to Africa's Olduvai Gorge and beyond, it is a journey revealed only in our own century, as biologists, geologists, paleoanthropologists, and others make surprising discoveries and shape brilliant theories to explain the lineage of the planet and everything that lives upon it.

"Origins" brings to life the struggles between widely accepted views and radical new ideas; between those who try desperately to define unexpected evidence in traditional terms and those who quickly grasp that this evidence implies a new way of thinking about our world and the fundamental nature of life.

In 1913, when radioactive rocks disclose that the Earth is billions -- not millions -- of years old, many of the world's most respected scientists are stunned. Their view of the world will have to be drastically rethought. Clever minds contort themselves to evade the implications of this convincing but unexpected evidence. Can it be that our home planet is unimaginably old? That Homo sapiens is a virtual infant as a species?

As some strive to piece together the origins of the planet, others seek to chart its evolution.

The idea that the continents had at one time formed a single enormous land mass that split into continents and drifted apart was the subject of intense theoretical argument in the early 1900s. It takes over fifty years for mainstream geologists to amass enough evidence to accept meteorologist Alfred Wegener's dazzling insight that the continents are not fixed in place upon the surface of the Earth; his vision contradicts more than seventy years of accepted geological teaching. But by the 1960s, most geologists come to embrace plate tectonics, a unifying theme for understanding the outer shell of the planet. They believe that the Earth is indeed made up of huge plates in constant motion, and that earthquakes, volcanic eruptions, and the formation of mountain ranges result from the gradual but steady movement of the Earth's crust.

The theories that Earth scientists and evolutionary biologists have wrestled with throughout the century have stirred more controversy than in almost any other field of science -- perhaps because the accelerating accumulation of evidence about human origins in the fossil record and in the genes rock our most fundamental beliefs about ourselves and our planet.

In 1912, England's Piltdown Man -- a human-like skull with an ape-like jaw -- is trumpeted as the missing link between apes and man. Although it is exposed as a hoax in 1953, the world is reluctant to acknowledge Raymond Dart's 1924 discovery of the real thing in South Africa -- and, thus, the African origin of modern man.

To trace our understanding of evolution -- a theory still today regarded as mistaken or even blasphemous by many -- "Origins" travels to 1925 Dayton, Tennessee for the Scopes trial. As defense council Clarence Darrow engages prosecutor William Jennings Bryan in what fast becomes a debate about the scientific accuracy of evolutionary theory, humanity's conception of itself is challenged by new evidence about the history of humankind.

Early in this century, Thomas Hunt Morgan's studies of the humble fruit fly reveal how genetic material is passed from parent to offspring via chromosomes -- giving rise to the tantalizing and terrifying realization that information defining a person's entire being can be encoded in a single cell. By mid-century, James Watson and Francis Crick uncover and describe the structure of DNA.

In fewer than 100 years, predominant thinking about the age and nature of the Earth -- and our place in it -- changes dramatically. A planet once considered stable is revealed to be dynamically evolving; the mechanisms of heredity are explained and will likely be charted down to the last identifiable gene.

"Origins" also ponders the century's earthly -- and cosmic -- lessons in humility. Earthquakes and volcanoes are startling proof and potent reminders that under our feet surges an ocean of liquid rock. The Earth's solar system is not the center of the galaxy. Our galaxy isn't even the center of the cosmos. Humanity is but a single link in a chain of an ancient, largely accidental process known as evolution. If the history of the Earth were compressed into twenty-four hours, the entire history of the human species would fit neatly into about the last second of that day.

The search for beginnings has led twentieth-century scientists on an astounding, if sometimes divisive, journey. Conflicting views of how life began and evolved on Earth have pitted creationists against evolutionists and scientists against each other for the last hundred years. We find ourselves on a planet far older and more dynamic than we ever suspected, and a part of a family tree more complicated than we ever imagined.

It is clear that the course of twentieth-century Earth science, genetics, and anthropology are nowhere near a final destination. The next adventures in the odyssey of science are likely to be as unexpected and revolutionary as those we are just beginning to understand.

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Major funding is provided by the National Science Foundation.

Corporate sponsorship is provided by IBM. IBM is a registered trademark of IBM Corporation.

Additional funding comes from public television viewres, the Corporation for Public Broadcasting, The Arthur Vining Davis Foundations, Carnegie Corporation of New York, and Becton Dickinson and Company.