Richard Leakey, a fossil hunter and elephant advocate, died at the age of 77.

Richard Leakey, a world-renowned Kenyan conservationist and fossil hunter whose revolutionary findings helped prove that humanity developed in Africa, died on Sunday at the age of 77, according to Kenya’s president.

Despite skin cancer, renal and liver illness, the famed paleoanthropologist stayed active far into his 70s.

“I got the terrible news of Dr. Richard Erskine Frere Leakey’s passing this afternoon… with deep grief,” President Uhuru Kenyatta said in a statement late Sunday.

As the middle son of Louis and Mary Leakey, probably the world’s most famous discoverers of ancient hominids, Leakey was destined for paleoanthropology – the study of the human fossil record.

Leakey began his career as a safari guide, but things changed when, at the age of 23, he was awarded a National Geographic Society research grant to dig on the shores of northern Kenya’s Lake Turkana, despite having no official archaeological training.

With the discovery of the skulls of Homo habilis (1.9 million years old) in 1972 and Homo erectus (1.6 million years old) in 1975, he led expeditions that re-calibrated our understanding of human evolution in the 1970s.

Following that, a TIME magazine cover featuring Leakey posing with a Homo habilis mock-up with the headline “How Man Became Man” was published. In 1981, he became even more famous after starring in “The Making of Mankind,” a seven-part BBC television series.

But the most renowned fossil discovery was yet to come: Turkana Boy, an astonishing, nearly-complete Homo erectus skeleton discovered during one of his expeditions in 1984.

Leakey rose to prominence as one of the world’s leading advocates against the then-legal worldwide ivory trade as the massacre of African elephants reached a crescendo in the late 1980s, driven by insatiable demand for ivory.

In 1989, President Daniel arap Moi nominated Leakey to manage the national wildlife agency, which would later become known as the Kenya Wildlife Service, or KWS.

That year, he pioneered a stunning PR stunt by lighting a pyre of ivory, igniting 12 tons of tusks to demonstrate that elephant tusks have no value once they have been removed.

He also kept his cool when enforcing a shoot-to-kill order against armed poachers, without apologizing.

His small Cessna plane crashed in the Rift Valley, where he had earned a name for himself, in 1993. He lived, but both of his legs were amputated.

“At the time, I was regularly threatened and lived with armed guards. But I decided not to be a thespian and instead declare, “They tried to kill me.” He told the Financial Times, “I choose to get on with life.”

A year later, Leakey was fired from KWS and embarked on a third career as a major opposition politician, joining the chorus of voices against Moi’s corrupt rule.

His political career, on the other hand, was less successful, and in 1998, Moi rehired him to lead Kenya’s civil service, tasked with combating official corruption.

However, the mission proved to be difficult, and he quit after only two years.

In 2015, when Africa was gripped by yet another elephant poaching catastrophe, President Kenyatta requested Leakey to return to KWS as chairman of the board, a position he would hold for three years.

Leakey “worked bravely for a better country,” according to Deputy President William Ruto, and “inspired Kenyans with his zest for public service.”

Leakey, who is soft-spoken and appears to be devoid of personal vanity, resisted giving in to his health problems.

“Richard was a very good friend and a true loyal Kenyan. May he Rest In Peace,” Paula Kahumbu, the head of Wildlife Direct, a conservation group founded by Leakey, posted on Twitter.