In Los Angeles, I meet with virologist Dr. Luis Villarreal, one of the main proponents of this theory. "I marvel at the capacity of viruses to create and destroy," Villarreal tells me. "They are our ancestors . . . If we respect humans, I think we have to respect the viruses that made them."

Respect viruses?

When I started this project, I have to admit my knowledge of viruses was limited. I thought they were simply microscopic agents that infect cells causing sickness, like the common cold or flu, or maybe even lead to death like HIV. But clearly there's more to viruses than I ever imagined.

From the jungles of Cameroon to the city of Atlanta, from the wilds of Montana to a ranch in Texas and labs in Los Angeles, I've been tracking virus hunters and other investigators that are writing a striking new chapter - albeit controversial - in the story of life on Earth. Many are beginning to suspect that long ago viruses jump started evolution, leading to the emergence of complex life; that viruses may have played a role in the emergence of humans from the primate line; that viruses changed the way the young are born; and that viruses may even be responsible for the emergence of complex behaviors and even the emotion we call "love."

As a filmmaker traveling around to document this story, it is clear that this is a rich topic that might change the way we think about who we are and where we come from. But there is one striking challenge we face wherever we go to film: how do we visualize a story when the main characters - viruses - are practically invisible?

Working with Director of Photography Mark Knobil, and animation genius Andy Murdock, director of Lots of Robots, we daily develop an off -the-wall plan. The film is being shot as a story that's being written by Dr. Luis Villarreal, and we literally see the world through his imagination.

For example, late one night in a diner, we shoot Villarreal as he postulates into a tape recorder that viruses might have lead to the emergence of humans from the primate line. To help tell this story, the diner is magically filled with miniature, animated chimpanzees that run along the counter and swing from the lights. Animated viruses attack the chimps as we learn how viral invasion changed the chimps basic blue print, or DNA, in ways that ultimately lead to humans. In other scenes, Villarreal walks the streets of Los Angles late at night, which are filled with a rich menagerie of creatures, from elephants to dinosaurs.

Producing this film is really pushing our creativity. And it is giving us something profound to think about. As biologist Nathan Wolfe told me in Cameroon:

"[T]he notion that [viruses] could simply be harmful is absurd . . . [L]et's say you had a switch on the wall, and if you flipped that switch you can eliminate viruses on the planet. Many people might think, "okay, I would flip that switch." But the reality is, if you did flip that switch, many of us who study viruses think that the world would come to a screeching halt"