Over 60 years after an heir of one of America’s wealthiest families vanished off the coast of a remote island inhabited by cannibals, questions still swirl over what may have caused his untimely disappearance – or death. 

Michael Rockefeller, the youngest son of then-New York Gov. Nelson Rockefeller, was just 23 years old and a recent Harvard graduate when he departed for a months-long trip to the island of Dutch New Guinea, a region inhabited by the Asmat, to collect indigenous art for a Museum of Primitive Art exhibition. 

The Asmat people were particularly talented in woodcarving, decorating elaborate spirit masks and ancestor "bisj" poles. Despite their artistic beauty, they were also known for headhunting and cannibalism, rooted in their spiritual beliefs. 

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Mr. and Mrs. Rodman Rockefeller and Michael Rockefeller depart for brother Steven's wedding in August 1959. (Tom Gallagher/NY Daily News via Getty Images)

In 1961, Rockefeller and anthropologist René Wassing were seven months into the excursion when their catamaran overturned in rough waters, leaving the pair and two local teenagers clinging to the wreckage. In an attempt to save their lives, the young art collector decided to swim to shore in search of help and was never seen again.

"When people vanish, it is incredibly unsatisfying and there's no closure," Carl Hoffman, author of "Savage Harvest," told Fox News Digital. "Just as Amelia Earhart remains fascinating to people, so is the death of Michael Rockefeller."

Hoffman, whose novel dives into the tale of Rockefeller and the lives of the Asmat, spent years pouring over archival materials and meeting with villagers in the region before coming to his own conclusion regarding what may have happened in the 23-year-old’s final moments. 

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Michael Rockefeller disappeared during an expedition to New Guinea in 1961. (T. Nielsen/Keystone/Hulton Archive/Getty Images)

A native Asmat stands near Dendrobium orchids in the Asmat area in 1950. (Bettmann Archive/Getty Images)

After the travel party’s homemade catamaran flipped, leaving the group to drift in the ocean for over 24 hours, Rockefeller strapped empty gasoline cans to his waist and swam for help. 

"Michael said, ‘I'm going to do it, I am going to swim,’" Hoffman said. "And his last words, as Wassing reported them, were, ‘I think I can make it.’"

While Wassing was rescued by the Dutch government, a two-week search failed to find Rockefeller. 

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New York Gov. Nelson Rockefeller speaks to reporters during a press conference about his missing son, Michael, on Nov. 29, 1961. (Bettmann Archive/Getty Images)

A native of New Guinea holds a piece of primitive art. (Bettmann Archive/Getty Images)

Different theories surround his disappearance – such as an untimely brush with a shark or crocodile – with the vast majority of speculation landing on the belief that the young adventurer drowned as he swam for his life. 

"The most sensational rumor was that he had encountered men from the Asmat and they had killed and eaten him," Hoffman said. "It was always this great mystery."

Hoffman’s research revealed two priests in the region who heard rumors that Rockefeller had encountered members of a nearby tribe upon arriving on the island. 

"[They] immediately started hearing stories that men from one particular village – the village from Ochenep – had been at the mouth of a river," Hoffman told Fox News Digital. "[They] had encountered an exhausted [Rockefeller] swimming up to them, and they had killed him, taken him to a very specific place and performed the sacred Asmat rituals on him in order to restore balance." 

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Nelson Rockefeller with Mary Todhunter Clark and their children, Anne, Mary, Steven, Rodman and Michael on Nov. 18, 1958. (Keystone-France/Gamma-Keystone via Getty Images)

According to Hoffman, the priests documented their findings, but the reports were only ever shown to the Dutch government and the apostolic vicar – the highest Catholic official in the Netherlands. The Rockefeller family was reportedly made aware of the rumors, resulting in them reaching out to Dutch officials, who allegedly swept the claims under the rug. 

The young Rockefeller’s passion for indigenous art is reflected in the newly renovated Michael C. Rockefeller Wing of New York City’s Metropolitan Museum of Art. The wing showcases 16 galleries of art, including works from Oceania, Africa and the ancient Americas. 

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"Opened to the public in 1982, the addition was named after Nelson Rockefeller's son, Michael C. Rockefeller, who was greatly inspired by the cultures and art of the Pacific and pursued new avenues of inquiry into artistic practice during his travels there," according to the Met's website. "Among the wing's signature works are the striking Asmat sculptures he researched and collected in southwest New Guinea."

The Met did not immediately respond to Fox News Digital's request for comment. 

While the mystery surrounding Rockefeller’s disappearance may never be solved, his legacy will live on through the artwork of the people who may have been the ones to end his life.  

"There was nothing primitive about the Asmat at all," Hoffman said. "They were this fantastically rich, complex culture that had 17 tenses and produced this art that was a direct view into archetypes and of the human unconscious, the human mind – and that's a fantastic thing. It's mind-opening, and it's mind-expanding, and it’s inspiring."