“Why did leaps in human evolution take place? “First Steps” explores a provocative “big idea” that sharp swings of climate were a key factor.”

NOVA provides some answers to these questions in an exceptional one-hour program, aired November 3, 2009 on PBS.

Here are some excerpts from the transcripts:

“NARRATOR: …… The new discoveries about ancient climate upheavals in Africa have led Rick Potts to formulate a bold theory of human evolution.

RICK POTTS:The traditional idea we have had about human evolution is that it was the savannah, the grassy plane with some trees on it that was the driving force. But instead, what we’ve discovered is that climate changed all the time.

And so the idea that we’ve come up with is that variability itself was the driving force of human evolution, and that our ancestors were adapted to change itself.

NARRATOR: It is a simple but revolutionary idea: human evolution is nature’s experiment with versatility. We’re not adapted to any one environment or climate, but to many; we are creatures of climate change.

MARK MASLIN:I think we should actually look to our proud ancestry and how we evolved in East Africa and say, “That’s how we survived that. We can survive the future, because we are that creature, because we are that smart.”

NARRATOR: Today, climate change seems to threaten our survival, but it may have held the keys to the astonishing story of how we became who we are, because it didn’t stop 2,000,000 years ago. These dramatic upheavals would continue for another million and a half years, propelling our ancestors down a road leading, ultimately, to the smartest creature the world has ever known.”

“Where did we come from? What makes us human? An explosion of recent discoveries sheds light on these questions, and NOVA’s comprehensive, three-part special, “Becoming Human,” examines what the latest scientific research reveals about our hominid relatives.

Part 1, “First Steps,” examines the factors that caused us to split from the other great apes. The program explores the fossil of “Selam,” also known as “Lucy’s Child.” Paleoanthropologist Zeray Alemseged spent five years carefully excavating the sandstone-embedded fossil. NOVA’s cameras are there to capture the unveiling of the face, spine, and shoulder blades of this 3.3 million-year-old fossil child. And NOVA takes viewers “inside the skull” to show how our ancestors’ brains had begun to change from those of the apes.”

Go to  NOVA to watch Becoming Human Part 1: First Steps.