Richard Leakey's story is so extraordinary and so packed with drama - so much, in fact, like the plot of a Hollywood movie - it's no surprise to learn that Angelina Jolie is going to make a film about him.

Africa, which is due for release late next year, has the starriest cast in the galaxy. Jolie has chosen her husband, Brad Pitt, to play Leakey while she will take the role of his wife and Meryl Streep will play his mother.

When I was at university, studying for a master's degree in palaeoanthropology (human evolution), my friends and I worshipped the Leakey family. Between them, Richard, his parents (Louis and Mary) and his wife (Meave) have discovered a significant proportion of the fossils that have revealed how human beings evolved. For a group of atheists, the Leakeys were the closest thing we had to idols.

Richard Leakey is better known, however, as a conservationist and a politician. His life has been a turbulent mix of adventure, triumph, strife and misfortune, all played out against the colourful backdrop of Kenya. In an African nation beset by poverty and crime, Leakey has battled against a political system disfigured by corruption and cronyism.

We meet at the Mandarin Grill & Bar, in the Mandarin Oriental hotel, Central. Leakey is in Hong Kong on a whirlwind trip, to give a series of talks, host the Royal Geographical Society's gala dinner, meet sponsors, promote local tour company A2A Safaris, tell everyone about the movie and raise awareness of the plight of elephants in the world's largest ivory-buying market. With a schedule like that I'm lucky to get time with him.

Leakey has a huge presence and masses of charisma. Pitt will have to act his socks off if he is to convey the charm, force and complexity of the real thing, not to mention the sonorous voice, with its very British accent. Leakey weighs his words with care and delivers them with authority. He's famously good at fundraising and it's easy to see why people find him persuasive.

As we talk, a crowd gathers to listen. They admire a photo of Leakey as a young man on the cover of a book and debate whether Pitt measures up in the looks department. They decide that he doesn't quite. At 70, Leakey's face is now mottled with skin cancers but he remains a handsome man.

Africa is loosely based on Wildlife Wars, Leakey's memoir of the late 1980s and early 90s, when he successfully combated ivory poaching in Kenya. Having done it before, there's room for hope that he can do it again, although the scale of the challenge is daunting.

"The threat to elephants is greater than it's ever been," says Leakey. "It's partly because the human population in Kenya has increased and people need to make a livelihood, but particularly because the economies of Asian countries, especially China, have grown exponentially.

"Ivory is part of Chinese culture and history - it's a commodity that indicates a certain status. If we're serious about saving a species as important and as symbolic as the elephant, then we've got to bite the bullet and say, 'We don't need ivory.' It's complete and utter nonsense to say, 'We need it.' What modern society needs is a healthy environment across the planet, and that includes elephants."

It's estimated that 33,000 African elephants are killed for their ivory every year. Last year, a tipping point was reached: more elephants are now being killed than are being born. With only 350,000 left in the wild, they could be driven to extinction within a decade. And it's not just elephants - rhinos are being slaughtered for their precious horns (worth more than twice the price of gold) and lions and other big cats are also under attack.

Africa is part of Leakey's strategy. He thinks the film could be enormously influential in changing public opinion.

"If the Chinese public hear the message coming not from Richard Leakey but from Brad Pitt, it'll have a far bigger impact. A really good blockbuster that wins awards and nominations, and leaves the audience feeling very positive and sympathetic to elephants, could be a talking point for years."

Leakey suggests people in China are unaware of how ivory is obtained.

"They might think it comes from elephants that died naturally," he says. "And they don't understand the fragility of the species."

The film will show them the horrifying truth.

LEAKEY MET LONDON-BORNMEAVE when she was studying monkeys in Kenya. They married in 1970 and have two daughters, Louise and Samira. Africa won't paint the most flattering portrait of their marriage since it involves "lots of girls and mistresses and all of that". Leakey says that "while it might cause periodic blushes", his wife doesn't mind. "If a hyped-up drama based on grains of truth can help win the fight, we'll do it. We're not teenagers any more."

In Kenya, Leakey is working to mobilise the public and drive legal reforms through WildlifeDirect, the activist organisation he co-founded in 2004. His team was instrumental in the introduction of stringent laws last year; now, anyone caught leaving the country with any amount of ivory on their person faces life imprisonment. As a consequence, poaching in Kenya has lessened.

However, Kenyan ports remain the primary gateway for ivory smuggled to the Far East from Tanzania and central African nations. The supply chain is run by criminal gangs who pay poachers, drivers, park rangers, police officers, customs officials and shipping agents to either help out or turn a blind eye. Dismantling the industry won't be easy.

Nevertheless, "I can take a very 'hard talk' approach", says Leakey. "As a Kenyan institution, run by Kenyans, [WildlifeDirect is] able to criticise government policy without the pejorative sense that this is a foreign outfit telling them what to do."

But there's a flip side: "The people doing the talking can still get into a lot of trouble in a system that's potentially repressive. Sometimes you step up to the plate and say what needs saying and, as a national, you might end up taking the stick for it, because they can't throw you out."

Leakey might be a Kenyan but he's a different colour to most of his countrymen. What was it like growing up as a white boy in British-ruled Kenya in the 40s and 50s?

He's quick to correct me.

"It's more a question of what it was like growing up in Kenya, because most of the time I was unconscious of the fact I was white. Colour has never been a factor in my life. In fact, the only people who made me aware that I was white were the white people." He says he feels "both white and black".

His was a special childhood. Leakey's parents found fossils that revolutionised our understanding of human evolution. They established that the birthplace of our species, Homo sapiens, was Africa and, from there, our ancestors spread out and colonised the planet. Young Richard accompanied his parents on excavations "to the wild and woolly lands of Olduvai Gorge and Lake Victoria".

When at home, he spent much of his time charging around the savannah on his pony, spooking the zebras and smacking the rhinos on their well-armoured behinds.

At his colonial, whites-only school, though, he was bullied for being a "nigger lover". Such was the prevailing culture that he received no support from his teachers.

He left school at the first opportunity and ran a safari company for a short time before joining the family business. Leakey spent 25 years as a palaeoanthropologist.

Serendipity struck in 1967 while he was flying over Lake Turkana, on the border between Kenya and Ethiopia. Looking down he observed that the lake's shores might be good fossil-hunting territory. Returning later by helicopter, he found a treasure trove. He sought funds and started digging. Over the next 20 years, Lake Turkana's sedimentary deposits yielded an extraordinary bounty of bones and stone tools.

Leakey and his team's most important discovery was Turkana Boy, who was aged nine to 12 when he died, 1.6 million years ago. Most fossil finds comprise single teeth or fragments of bone so this almost complete skeleton, a member of the pre-human species Homo erectus, was a startling discovery.

At university, learning about Turkana Boy and his relatives, I dreamed of joining the anthropologists at work under the blazing African sun, unearthing fossils that would answer the most important questions of all: who are we? And how did we become this? From the vantage point of a chilly English lecture hall it all seemed impossibly glamorous and exciting.

Leakey's recollections suggest that those romantic visions were - surprisingly - spot on.

"I loved finding fossils. There's an amazing buzz from feeling you're right on the cusp, on top of the pack, driving forward the quest for new knowledge. It was heady stuff for a young man."

I ask him why he thinks it's an important subject. His answer comes as another surprise. Evolutionary studies act implicitly to rebuff creationist theories, but I'd always assumed that was a consequence, rather than a motivating factor, for scientists - probably because I grew up in a largely secular country.

"In the developing world, religion has played a very big part in getting people to line up about moral codes and approaches to problems. You hear in places that it's 'God's will' that the rain has disappeared, that the oceans are rising, that people get diseases - it's 'inshallah'.

"Science can now give people a certainty about what we are that religion gave their parents and forefathers. If we're going to keep this planet from disaster it's especially important to educate boys and girls in the developing world that their destiny belongs to them. It won't be decided by a god, but by their knowledge and commitment to build the planet."

Leakey says that, even 30 years ago, a Darwinian explanation of human evolution couldn't be substantiated due to the lack of fossil evidence. That's no longer the case.

"The amount and the quality of what has been discovered makes it almost as solid a science as chemistry or physics. How we have failed, and continue to fail, is in bringing the world with us. Scientists know, but people in many parts of the world don't know. I think it's our fault because we haven't taken the trouble to go and preach every Sunday."

Leakey worked as head of Kenya's National Museum until 1989, when he switched careers. Kenya's then president, Daniel arap Moi, asked him to take over the Wildlife Conservation and Management Department (shortly after superseded by the Kenya Wildlife Service) in response to the international outcry over poaching.

When Leakey took the helm, the department was a mess. A lack of funding and entrenched corruption had left staff ill-equipped and demoralised while elephants were sitting ducks for poachers. Leakey took characteristically bold steps, tackling both the supply and demand ends of the ivory trade. He announced his arrival by organising an event at which millions of dollars' worth of confiscated ivory tusks were piled into a "macabre sculpture" and set alight. The giant bonfire made global headlines. Impressed, the World Bank granted him US$150 million for conservation programmes.

Leakey cleared the department of dishonest staff and lobbied successfully for a world ban on ivory trading. He also took on the poachers, implementing a much-reported "shoot-to-kill" policy.

"That's a complete misconception, perpetrated by the press because they love Rambo stuff," he says. "We never implemented a shoot-to-kill policy and it's not something I believe in."

Conscious I'm a member of the guilty profession, I ask him to tell the true story.

Leakey says that when he took over, about 70 rangers were being killed every year. Armed with Enfield rifles dating from the first world war, they were hopelessly outgunned by the poachers, mostly demobilised militia from Somalia carrying modern assault rifles.

"I re-armed my men, had them properly trained and made it clear that if you shoot a man in uniform in a wildlife area, fire will be returned and you will likely die. But I told my men that I'd much prefer they capture their quarry alive, as there's nothing more useful than a turncoat."

Whatever the policy, the body count was high. Poachers invariably chose to fight to the death rather than surrender.

Leakey's diary entry for July 3, 1989, as published in Wildlife Wars, reads: "On the poaching scene we seem to be making good progress. I believe the number of poachers killed during June was 22 and about 7 captured or wounded."

His tactics were phenomenally effective and within six months the poaching problem had evaporated. Leakey was the toast of the international media but, at home, he'd stirred up a hornet's nest. Ending the lucrative trade earned him powerful enemies.

In 1993, Leakey was piloting a light aircraft when the engine cut out. He managed to crash-land in a field but his lower legs were crushed. The infection that set in nearly killed him, and both legs had to be amputated. He now walks on prosthetic limbs.

It has never been proven that the plane was sabotaged, but Leakey has no doubts.

"I lived under considerable pressure, with numerous death threats. It's widely accepted that it was an attempt to kill me. Could we prosecute somebody for it? No. Do I want to? No. The person who probably stage-managed it - who I can't name - is somebody I'm quite friendly with.

"That's weird," I say.

"That's Africa," is all he will add on the subject.

Leakey mentioned earlier that Jolie's film will explore how his choices affected his family and caused arguments. How did his wife feel about him exposing himself to such danger?

"Meave wanted me to pull back. She wasn't happy about me going into wildlife because I'm very outspoken and very confrontational. I'm not able to deal with things subtly." He parodies his own attitude, "If you're bad then I'll tell you you're bad, and I'll make you good, dead or alive!

"My wife is extraordinarily understanding and tolerant. She knows the man she married. I'm not pleased to say it but I've always wanted to do things my way. That's part of the package. Probably not a very attractive part, but there it is."

After five years heading the Kenya Wildlife Service, Leakey was finally outmanoeuvred by his foes. They launched a smear campaign, accusing him of arrogance and racism and of valuing Kenya's wildlife more than its people. Stripped of his powers, Leakey resigned, but that didn't mark the end of his battles in the political arena. He established an opposition party, Safina, and won a seat in parliament in 1997.

Two years later, Moi asked Leakey to join his administration, appointing him as cabinet secretary and head of the civil service. International donors had lost faith and frozen Kenya's aid payments, and Moi hoped that Leakey would help him regain their trust. The partnership didn't last - Leakey's efforts to clean up corruption were stymied by vested interests and, in 2001, he was forced to step down.

Having hit retirement age, Leakey is showing no signs of easing off the throttle, despite a medical history that would have consigned most of us to permanent bed rest. Leakey's kidneys failed many years ago and both have been replaced. In 2013, he had to undergo a liver transplant, after which the doctors thought he might die.

I ask him how he has managed to cope with ill health.

"What ill health?" he asks. "What nonsense. I'm as fit as a fiddle."

In recent years he has returned to his first passion, palaeoanthropology. He was appointed professor at New York's Stony Brook University in 2002 and established the Turkana Basin Institute, a field station for scientific research. Previously, all significant fossil finds in the area were dispatched to museums in the capital, Nairobi, but now they are kept at the institute.

"I want to make the Turkana people stakeholders in their own heritage," says Leakey. "I want to show them these wonderful things and say, 'Come and work here, be the discoverers, be the technicians, be the students doing PhDs.'"

He's also hatching a pair of ambitious plans with Polish-American architect Daniel Libeskind.

The first involves the Serengeti, an area that extends across a large swathe of Tanzania and Kenya, and plays host to the annual migration of more than 1.5 million wildebeest, as well as zebras, gazelles and other animals. For some years, an argument has raged over plans to build a multi-lane highway across the Serengeti, to facilitate the export of oil and minerals from central Africa to China. The road would block the migration, with untold consequences for wildlife. Conservationists have successfully stalled the project thus far but Leakey is convinced the road's construction is inevitable. He and Libeskind have proposed building an elevated highway, which will soar above the plains, leaving the wildebeest to continue their long march underneath.

Their second project is to build a museum - "an architectural masterpiece" - on the shores of Lake Turkana, which will celebrate the area's fossils and tell the story of human evolution.

"It's for the African diaspora - and that's everybody in the world. It'll be like a pilgrimage; come and see where you came from."

Leakey is seeking US$40 million to realise his dream.

"It'll be the greatest museum of mankind ever built. Somebody could make their place in history. Their name will be there forever. If you've got the money to spare, come and talk to me."

The inveterate fundraiser asks me if I'll help him spread the word. The idea sounds wonderful, so I promise that I will do my best.

BY THE SAME AUTHOR: Eric Cantona, an artistic butterfly