Documentarian James Marsh, whose previous Oscar-winning film Man on Wire detailed the life and vertiginous exploits of French high-wire daredevil Phillippe Petit, homes in on another fascinating subject in this cradle-to-the-grave, nature-versus-nurture doco about a chimp raised to be a human.

Loads of archival footage and photographs interlaced with re-enactments and interviews from people close to the primate protagonist form the crux of Project Nim (film #23), which details the tumultuous life of a chimpanzee at the centre of a bold experiment launched in the 70s to determine whether chimps can, with sign language, communicate on the same basic linguistic level as humans.

Professor and project creator Herbert S. Terrace placed Nim in the care of a hippy family, with one instruction: to treat him like a person and not an animal. Nim sucked the breast of his adopted (human) mother, went to the toilet, wore t-shirts, asked for hugs and toked on reefers. But when Terrace feared Nim’s anything-goes home wasn’t right for his development and certainly not for the overarching experiment, he moved Nim elsewhere and set in motion a chain of events that rocked the foundation of the chimp’s already unusual fish-out-of-water life.

Project Nim is more a character than a creature study, a deeply personal film with an odd twist given the “person” at the heart of it. Marsh frames the story in straight-up no-frills documentary style, relying on the uniqueness of his subject material to sustain interest, which it certainly does.

The film’s interviewees, some of which could have been written off as one-dimensional evil animal testers, are empathetic people who struggle with shared conundrums and moral questions. Is it right to put a chimp in a cage after raising it in a house? Does a chimp raised as a human deserve basic human rights? And, in one wacky but legit argument, if a chimp has been raised as a human, is it legally entitled to appear in a court room?

While collecting thoughts on a film carried by such a touching but unusual and unnatural premise, one might be tempted to write something along the lines that Project Nim spotlights the animal in humans beings and the human beings in animals. But such a line is too neat, too convenient, too easy to bang off on the keyboard, and this engrossing experience – a great companion piece to Werner Herzog’s unforgettable portrait of bear lover Timothy Treadwel in Grizzly Man (2005) – is more complex than a “we’re all kind of the same” summation. It’s a rare film that challenges preconceptions about the differences between humanity and the animal kingdom.

Project Nim will be released in select cinemas nationwide on September 29.