A Beautiful Truth is the extraordinary, rather beautiful and experimental new novel from the Canadian writer Colin McAdam, but where on earth did it come from?

The plot is unusual to say the least - it's about a couple who cannot have children and decide to adopt a chimpanzee instead - but even more daring is the fact that it is the chimpanzee, not any of the humans, who's the central character. As the animal struggles to adjust first to life in a suburban house, then in a vivisectionist's lab, we share his thoughts, his emotions and his pain.

McAdam thinks there were probably two sources of inspiration for this idea. The first was a playground in the centre of Montreal, where he lives. When I call him up in Canada, he tells me about the day he took his young daughter there and watched her playing with friends and the parents sitting around on benches chatting.

"Strip away our clothes and look at it from above, and you have a beautiful collection of apes right there," he says. "If you know even a little about apes and open your mind to that, it's inarguable what we are."

The second source for A Beautiful Truth was an animal sanctuary in Canada called Fauna. It's a place that re-homes chimpanzees that have been neglected or abused by the vivisection industry, and McAdam spent some time there when he was thinking about writing the novel. At first he was in awe of the physical presence of adult chimps: their power and charisma. He also realised he was guilty of thinking that all chimps look the same. They are as different, he says, as semi-naked bodies on a public beach.

McAdam, who talks in a gentle Canadian accent, lowers his voice a little as he tells me more about these encounters. He was allowed some close-up interaction with the chimps at Fauna and had different interactions with each of them at different times. Occasionally, the animals would invite him to groom or chase; at other times, they would wander off and sit on their own, just contemplating. After a while, McAdam found himself returning to one chimp in particular: a female called Pepper.

Pepper is about the same age as McAdam - early forties - and came to the sanctuary after spending many miserable years in vivisectionists' labs. "She had a medical file that spanned decades," says McAdam. "She was HIV-positive and had scores of challenges with hepatitis and other horrors. She survived those decades and ended up in this comfortable sanctuary, but she had to adjust to a group of strangers. Quite simply, I saw her as a woman."

As McAdam watched Pepper, the idea for the novel started to form. Seeing her in action, he says, knowing how she had adapted to what she'd been through, made him want to tell her story. To McAdam, it seemed like the classic stuff of novels - an individual fighting for a place in a group through a range of horrific encounters - and the fact Pepper was a wordless ape made it all the more appealing.

What he did next was change Pepper to Looee, change her sex, and build a novel around his new chimpanzee character. This is what makes A Beautiful Truth experimental and rare. Looee is not in the supporting cast of A Beautiful Truth, he is the central character, and that doesn't often happen in novels. When animals do appear it's either in satire like Animal Farm or Great Apes by Will Self, or it's in children's books such as White Fang or Black Beauty. It's highly unusual for a serious novelist to use an animal as the main protagonist and then do what a writer would do with any character: imagine their thoughts, emotions, expectations.

Perhaps the reason this is not done more often is because some readers would see it as silly or unrealistic (do animals really have emotions, they would ask). But McAdam manages to get it right in A Beautiful Truth. He can't know for certain what chimps think or feel, but he does perform an imaginative jump without it ever feeling wrong.

What makes the jump much more acceptable is it's based in part on what we are learning from the growing body of research on animal cognition. One recent example was what scientists observed at Blair Drummond Safari Park when a chimp called Pansy was dying. As she grew weaker, the other chimps groomed Pansy and sat with her through the night. For days after her death, they avoided the platform where she slept and died. The conclusion is easy: the chimps were grieving.

McAdam thinks humans are unprepared to accept this fact or what research into animal cognition means: that humans and chimps are alike.

"Humans don't like seeing themselves as animals," he says. "A lot of this comes from how we're educated, the fact primatology is a relatively new endeavour, and the truth that within our world most of our illusions are complete - many of us are so far removed from the rigours of survival that we need to have no understanding of the fact these bodies are those of apes."

McAdam tackles this issue in A Beautiful Truth by having Looee adopted by a human couple who have been unable to have a baby, although he also uses the story to remind us that we should also respect the differences between animals and humans.

The couple who adopt Looee are Walt and Judy, and Judy in particular takes the chimp into her arms as if he were her son. In one section, she rubs lotion into his body and catches herself thinking "there's a little boy's body under there"; later in the book, however, the relationship goes violently wrong when the chimp attacks her.

McAdam's point is that chimps and humans are like each other but that we are not precisely alike; we are close but there are dangers in getting too close. As one of the characters in his novel puts it: there is no human/animal divide, there is a continuum. What McAdam hopes is that this point will get through one day, although he's become used to blank looks in the audiences on book tours and he does want his book to be a novel, not a lecture.

What he also wants is an end to the kind of vivisection that Looee suffers in A Beautiful Truth and Pepper suffered in real life. On the day I call McAdam, the US government has announced it is planning to retire most of its research chimps, but it has also announced it will not be increasing the minimum size of cage that chimps can be kept in (in the book, Looee is kept in a cage that's five by five by seven feet, which is close to what is used in labs).

These snippets of good news and bad news leave McAdam realistic about a possible end to vivisection and, in a way, confirm his theory that man is just an ape himself. "What happens in the animal rights debates," he says, "is that one group vilifies another, and the rancour gets in the way of looking squarely at the fact that we are animals.

"Not only are we animals, we're social animals who choose groups and exclude others. We're apes, and vilifying those we don't agree with is classic ape behaviour. Vivisection is the behaviour of a species trying to survive, and I think survival is an inherently unethical business."

A Beautiful Truth is published by Granta at £15.99.