The death was confirmed by Trish Sewe, a spokeswoman from WildlifeDirect, an organization Mr. Leakey helped found to protect endangered animals. The cause was not disclosed.
Mr. Leakey was a third-generation Kenyan descended from English missionaries who went to Africa in the 19th century. He spent most of his life in his native country and always considered himself Kenyan and, in a broader sense, African. When Kenya became independent from Britain in 1963, Mr. Leakey chose Kenyan citizenship. He spoke Swahili and other African languages.
His parents, Louis and Mary Leakey, were celebrated paleoanthropologists who had been searching for fossils in East Africa since the 1930s. Their discoveries of skulls and other remains in Tanzania’s Olduvai Gorge helped prove that human life first emerged in Africa.
Mr. Leakey made his first fossil discovery at age 6 — the jawbone of an extinct giant pig — but throughout his youth he had no intention of following his parents’ profession. He quit school at 16, became a pilot and ran a safari business for a few years. But the lure of the fossil beds remained strong, and his discovery of a lower jaw from the genus Australopithecus, an early hominid, brought him back into the field.
Mr. Leakey, whose training came from his parents, did not attend college or call himself a scientist.
“I’m not a biologist. I’m not an evolutionist,” he told an interviewer for the Current Biography reference work in 1995. “I’m a naturalist.”
During a plane flight near the border of Kenya and Ethiopia in 1967, Mr. Leakey looked down and saw that the geological formation surrounding Lake Turkana (then called Lake Rudolf) could be a promising source of fossils. He did not tell his father about it until they were meeting officials of the National Geographic Society in Washington the next year. Mr. Leakey, then 23, asked for funding to begin exploring the site and received a generous grant.
He and a group of fossil hunters known as the “hominid gang” began excavating at Lake Turkana and soon unearthed many remarkable artifacts — which led to a sense of competition with his father and a years-long rift.
Mr. Leakey and his team found Stone Age tools almost 2 million years old, an Australopithecus skull and, in 1972, a 1.9 million-year-old skull from a large-brained species that was an ancestor of modern humans. The skull, which was known by its museum registration number of 1470, was eventually determined to belong to a new species, Homo rudolfensis.
Mr. Leakey showed the skull to his father, whose pride in his son’s discovery led to an immediate reconciliation. Louis Leakey died days later.
The fossil record at Lake Turkana led Mr. Leakey to propose a theory that different forms of early human life did not necessarily succeed each other in a continuous line of evolutionary progress. Instead, he said there was evidence that at least three different kinds of early humans inhabited the same place at more or less the same time, from 1.5 million to 2.5 million years ago. The idea is now widely accepted by scientists, who believe four separate forms of early humans lived there.
“He made East Africa the central playing field for the study of human evolution,” Lawrence Martin, director of the Turkana Basin Institute, which Mr. Leakey co-founded in partnership with New York’s Stony Brook University, said in an online National Geographic obituary. “By good luck, good fortune, good organization, hard work, he really hit on a place that’s turned out to be the mother lode.”
Mr. Leakey outlined his ideas in several books, including the best-selling “Origins” (1977) and “People of the Lake” (1978), both written with Roger Lewin. Mr. Leakey, who was on the cover of Time magazine in 1977 and was the host of a popular BBC series, “The Making of Mankind,” initially broadcast in 1981, believed that the first links in the human evolutionary chain reached back more than 7 million years.
Mr. Leakey described the thrill of discovering the skeleton in a 1992 book written with Lewin, “Origins Reconsidered”:
“How very human he looked in that setting! It was a moving moment for me. … This was a deeper emotion, one derived from the broad sweep of prehistory that I am privileged to see in my work. I realized I was face to face with a link in the chain that joins me, today, with the earliest human ancestors, apelike creatures who lived perhaps 7.5 million years ago.”
Richard Erskine Frere Leakey was born Dec. 19, 1944, in Nairobi, the second of three sons. (A sister died in infancy.)
He spent much of his childhood working alongside his parents. The family had close relationships with Kenya’s native Black populations, which once led Mr. Leakey’s White schoolmates to taunt him, lock him in a cage and urinate on him.
In the mid-1960s, Mr. Leakey went to Britain with the aim of continuing his education, but he ran out of money and returned to Kenya with the equivalent of a high school diploma. In addition to his field research and other projects, he began working for the National Museums of Kenya in 1968. He became the director six years later and was instrumental in making Kenya’s museums of science and culture among the best in Africa. He issued a ruling that all artifacts unearthed in Kenya had to remain in the country.
In 1989, Mr. Leakey was put in charge of the Kenya Wildlife Service, with the aim of reducing the poaching of wild animals, particularly elephants and rhinoceroses. Mr. Leakey persuaded the World Bank and other international donors to give $150 million to the country to improve animal conservation. He organized the burning of Kenya’s 12-ton stockpile of seized ivory to prevent it from being sold. President Daniel arap Moi gave park rangers the authority to shoot poachers on sight. Mr. Leakey resigned from the post in 1994, after disagreements with political leaders.
Blunt and outspoken, Mr. Leakey did not shrink from disagreements with scientists, political opponents or even members of his family. He kept a loaded gun in his briefcase.
“When I was head of the Kenya Wildlife Service I had five bodyguards, night and day, 24/7,” Mr. Leakey told Newsweek in 2014. “And I needed them. There were many, shall we say, interesting incidents.”
Mr. Leakey’s first marriage, to Margaret Cropper, ended in divorce. Survivors include his wife since 1970, the former Meave Epps, a paleoanthropologist who has made significant discoveries of her own; a daughter from his first marriage; two daughters from his second marriage; two brothers; and three grandchildren.
Throughout his life, Mr. Leakey was prone to illness and mishaps, beginning with a fractured skull in his youth. He developed an infection that led to chronic kidney disease and had two kidney transplants, including one in 1979 from a brother, Philip, from whom he had been estranged for 10 years. (Philip Leakey was the first White person elected to Kenya’s Parliament.)
In 1993, Mr. Leakey crashed his single-engine airplane — he suspected sabotage — resulting in the amputation of both legs below the knee. He learned to walk on prosthetics within weeks. After years in the sun, he developed many cancerous lesions that had to be removed. He had a liver transplant in 2013.
In the mid-1990s, Mr. Leakey helped form a new political party called Safina (Swahili for “Noah’s ark”) to challenge what he viewed as Kenya’s corrupt political leadership. He was attacked in the street by thugs with whips and clubs, but he was nevertheless elected to Parliament, along with several other members of his party.
He was named head of Kenya’s civil service in 1999, only to resign after two years because of political interference. From 2002 to 2015, Mr. Leakey divided his time between Kenya and New York, where he was an anthropology professor at Stony Brook University on Long Island and led the Turkana Basin Institute.
He returned permanently to Kenya in 2015, serving as chairman of the country’s wildlife service for three years and raising money for a proposed museum on human origins.
“I’m determined,” he said in 1996, “not to end up a frail old man in a wheelchair who’s done nothing and so has nothing worthwhile to look back on.”
Emily Langer contributed to this report.