It is past midnight and Jane Goodall is a study in grace and patience. She is on a book tour of Canada, far from her spiritual sanctuary of Gombe Stream on the green, humid shores of Lake Tanganyika. Her lecture ended over two hours ago and yet she is still signing books tirelessly.

She won't leave until she has spoken to the last person waiting in line, although she has a plane to catch at 6am and will be lucky if she gets four hours' sleep. Hardly anyone knows this, and she will not tell them. That is the kind of person she is. Earlier, Goodall had spoken to me of the strange journey that took her from her youthful love for Dr. Dolittle books to the shores of Lake Tanganyika and a life among the chimpanzees. She credits her childhood dog Rusty with giving her a curiosity about the natural world and the powers of observation to put that curiosity to use, and notes her strong spiritual connection with her mother Vanne.

An early trip to Africa with Vanne instilled curiosity and affection for the continent that would become her home, but she was in her early twenties and relatively untested in the field of science when she first badgered palaeontologist Louis Leakey into giving her a chance to prove herself. "He took me out to Nairobi National Park and gave me some lessons in stalking," Goodall recalls, with a wry laugh. "I think he made up his mind when we went to his dig at Olduvai Gorge at a time when there were no roads, nothing - just totally wild. He saw that I didn't panic and had the right instinctive reactions when we came across lion and rhino on foot. I think that was what did it - that, plus my unlimited enthusiasm and self-confidence." Leakey sent Goodall to study chimpanzees in part because he felt that learning about mankind's closest living relatives in their natural habitat would give him a better feeling for how our own early ancestors may have behaved. We can learn a lot from the bones as to what these creatures looked like, Goodall says; we can guess what they were eating from the wear on their teeth; we can form an idea from the tools found near their bones as to how they lived. But behaviour doesn't fossilise. Leakey argued that if Goodall and others found behaviour common to chimpanzees and human beings today, that behaviour was probably present in the early apelike creatures that may have been our common ancestor, and in Stone Age man himself.

Goodall encountered initial hostility from the scientific community because she was not formally trained. "I didn't really care what other people thought," she recalls. "I was lucky. I wasn't in academia fighting for a university job, so it didn't worry me. It would have been very different today." She breached scientific protocol by giving her chimpanzees names instead of numbers and focusing on their personalities, minds and feelings. This reflected local African thought: in Jennifer Lindsey's book Jane Goodall: 40 Years at Gombe, a Tanzanian villager recalls his first encounter with the strange young mzungu (white) woman who came to the forest near his village in 1960 to study chimpanzees. He explains his grandmother's tale of the chimps' origin. "On the occasion of Darkness Twice, when the moon's shadow covers the sun in the heat of the day, everyone must hide inside their house. If you are caught outside when darkness descends, you will become a chimpanzee - just like those who live in the forest now. Listen carefully: when you hear the distant pounding of the tree buttress, the chimpanzees are dancing in the forest, singing "We used to be people, but now we are not.'" Goodall was the first to witness chimpanzees making and using tools, to note their opposable thumbs, to identify and record individuals' behaviour and to compile a compendium of continuous observation. She gained a Ph.D. in Ethology from Cambridge and her work laid the foundation for all future primate studies. She has received numerous awards, including a CBE and the National Geographic Society's Hubbard Medal in 1995, and has written several books, most recently an autobiography (Reason for Hope) which explores her beliefs about spirituality and moral evolution. Her Gombe Stream project is the longest unbroken study of any animal group ever undertaken.

But it hasn't been easy. Goodall has suffered personal loss and made great sacrifices. She narrowly avoided being killed in a plane crash in 1974. She has witnessed war and genocide, survived break-ins at Gombe and her Dar es Salaam home, and overcome tropical diseases. She has also campaigned endlessly against the slaughter of forest animals for bush meat, the illegal trade in live animals as pets, the defoliation of the Congo Basin and the inhumane treatment of captive chimpanzees in zoos and laboratories. Yet Goodall perseveres. Ten years ago, she established a new organisation, Roots & Shoots, based on the idea that young people can work like roots and shoots in tackling seemingly intractable problems. "Roots creep quietly everywhere, making a firm foundation," Goodall observes. "Shoots seem so new and fragile, but to reach the light they can move boulders, break concrete." Roots & Shoots is a loose-knit network of activist clubs organising hands-on projects to help animals, people and the environment through hard work and compassion. The organisation started with roughly 700 members in Dar es Salaam; today it has offshoots in more than 65 countries worldwide. "Its main message is the importance of every single individual, how we all matter and can all make a difference," Goodall says. "My real charge in life comes when a group of kids show me what they've done."

"Unfortunately I can't be a Louis Leakey," Goodall says. "I can't wave a wand and say, ‘Go and study animals,' because these days people need degrees to get research permits. So I can't do for others what Louis did for me, which is frustrating." She advises children who want to follow in her footsteps: "You have to be really passionate because there's a lot of competition. It's not easy to get the money. I tell young people who think they want to go and study animals to first study animals in their own backyard - even your pet. Really study them; see what it's like to be that animal. And then write what you see."

Goodall believes the developed world has a great responsibility to preserve Africa's last wild places. "Who raped developing countries of their natural resources, destroyed their culture? Who put them in the position they're in today? The West. Then you have corrupt governments. We must help provide education, but we also have a tremendous responsibility to listen to local people and see what they think and feel."

Preserving biodiversity is the key to saving endangered species, believes Goodall, and understanding the concerns of people in impoverished areas is critical to protecting a country's natural heritage. "You can't help animals at the expense of people. You have to help both. It's a question of the need to survive together. We need this biological diversity of species. We need the natural world - psychologically, spiritually." "It is a very grim picture in Africa. Yet, there are such wonderful people there, such wonderful wilderness areas, such amazing animals. It's desperately worth trying to do something."