Project Nim, the latest doc from acclaimed director James Marsh, is the perfect case study for the nature versus nurture debate, with the story of a chimpanzee at the center of a 1970s experiment.

After Marsh read Elizabeth Hess’ book Nim Chimpsky: The Chimp Who Would Be Human, he felt the story would be the perfect story to follow up his Oscar-winning Man on Wire.

“It was a gripping and surprising story and as a filmmaker the challenge was definitely to see if I could create a biographical film focused on an individual animal, which I hadn’t quite seen before,” Marsh tells realscreen.

Chimpanzee Nim Chimpsky was just a baby when he was removed from his mother to live with a human family and learn sign language, in behavioral psychologist Herb Terrace’s early-1970s experiment. Project Nim tells the chimpanzee’s story from the POV of those whose moral and ethical decisions impacted his life.

At the time, the experiment received much attention from the press, so Marsh knew there’d be plenty of stock footage available for the film. However, there were some pleasant discoveries, like tape of Nim’s first encounter with another chimpanzee, which occurred after the experiment ended and he was taken to a chimp breeding facility.

“That was an extraordinary piece of archive for all sorts of reasons. You see Nim, who doesn’t quite know what he is at this point, see what he probably is, a chimpanzee. That interaction is extraordinary and very unsettling to witness,” he recalls.

Also found was archive footage of Nim being subjected to medical testing at a medical facility. “We could … understand exactly what he was going to face there. That was very important emotionally for that part of the story,” says Marsh.

In addition to the footage, Project Nim also features stylishly shot interviews with all of the living players who contributed to Nim’s life, including Terrace, Stephanie LaFarge, who raised the infant chimpanzee as her own, and a string of other female caretakers.

“We didn’t [value] the professor’s point of view over the people that essentially worked on the front line of this experiment, the women in a maternal role with Nim. It was kind of a level playing field that wasn’t true of the hierarchies at the time of the experiment. The appeal of the story was to understand our behavior in the context of a chimpanzee and what that chimpanzee brought out in us as a species as well,” says Marsh.

In addition to keeping a balance between all of the different points of view, Marsh also didn’t want to anthropomorphize Nim.

“One of the starting principles for me was not to take that easy option to look for characteristics of Nim that are human when he didn’t exhibit those behaviors, even though the experiment was to see how much they could bring a chimpanzee towards this,” he explains.

“For me the great discovery of the film was this nature vs. nurture discussion that’s implicit in the story. Nature was clearly a strong element in all of Nim’s behaviors and however much he was toilet trained and given signs to use, he remained a chimpanzee. His behavior in the film emerges very strongly as his natural hardwired behavior and that in a sense causes all sorts of complications for him when he lives with human beings as he gets older and stronger.”

Now that the film has premiered at Sundance Film Festival, where it was acquired by HBO (Roadside Attractions and HBO are partners on the U.S. theatrical run and DVD distribution), the film is out of Marsh’s hands – to a point. “In a documentary you start with a blank page, and I’m never quite sure that I’m finished any documentary film. At a certain point, you’re forced to kind of abandon them. And you hope you abandon them at the right moment. I hope I got that right.”

“Project Nim” plays at the Hot Docs Canadian International Documentary Festival May 5 at 9:45 p.m. EST and May 6 at 11:00 a.m. EST.