Grief, anger, childlike trust and even forgiveness. These are the emotions you read on the giant faces of 30 orphaned apes in a new photography exhibition at the Natural History Museum.

You would have thought that a gorilla is a gorilla is a gorilla. But no, every face is individual. Every wrinkle and scar reveals the suffering that those eyes have seen.

Over four years photographer James Mollison travelled as far as Indonesia and Cameroon to shoot gorillas, chimpanzees, orang-utans and bonobos rescued from the direst of conditions.

All but two of the 30 apes in his show had watched how poachers butchered their parents either to capture and sell the little ones as pets, or for the bushmeat trade.

Some cultures believe that eating the meat of big apes in their adult years enhances manhood, "like drinking snake blood", Mollison explains.

When Chim's parents were killed for the bushmeat trade, a Cameroonian environmental journalist kept her like a child. The chimpanzee was bathed, dressed and made to dance to receive human food.

Now living at Mvog Betsi Zoo in Cameroon, the five-year-old ape still dances when she is not fed on demand.

Reproduced at two metres high, her portrait stares at you in quiet hurt and fear.

With his pictures, Mollison aimed to make people think about the fate of the apes. What will happen to them? And to the few that are left in the wild?

Human destruction of their habitat is an even greater threat to their existence than the bushmeat trade.

Mollison also wanted people to confront their origins. "As man we are clearly different from a snake or a worm, but apes inhabit a grey area. We see this kind of connection."

His quest taught him how important touch is. Katie, a two-year-old chimpanzee, was rescued from a hunter who killed her parents and kept her in a small box in his hut. She had no physical contact with either man or animal and became mentally disturbed.

"She was not nice to be with," Mollison recalls. "She would try to bite you and kept to herself."

He photographed all the apes with a medium format camera from about 70 cm away. "I wanted the engagement, rather than using a long telephoto lens."

To get them to look into the camera, he often bribed them with a peanut. Or he looked for fleas on them a way of building trust. "When you pretend to find a flea, they want to see it, and that's when I take the picture."

The world's top authority on ape behaviour, Jane Goodall, helped him to relate to the apes.

Mollison, known for his Benetton campaign photos, got the idea for his project when he noticed how expressive the faces of primates were in a TV documentary by Sir David Attenborough.

His first subject was Shanga, a two-year-old gorilla in the Berlin Zoo, Germany, who had to be taken from her mother because she had no milk.

The last stop was the Republic of Congo, where Mollison's trekked for two days to photograph gorillas that had been reintroduced to the wild.

"There was an element of danger involved," he says. He could not understand his two guides and came down with cerebral malaria at the end of the trip.

The pictures started off as passport-type photos with the shoulders included. But because the apes kept moving, it was difficult to achieve consistency.

Mollison decided to crop them tightly, showing just the face with their intense eyes.

"They ask you questions, he says. "They are harder to look away from."

  • Face to Face by James Mollison runs at the Natural History Museum from 28 May to 18 September 2005. Admission free.