On November 19, 1961, Michael Rockefeller vanished. The 23-year old Harvard graduate and son of New York governor Nelson Rockefeller was in Netherlands New Guinea collecting the haunting wooden carvings of the Asmat people for his father's recently opened Museum of Primitive Art. On that November day, his boat capsized, and he swam toward shore. He was never heard from again.

The story of Rockefeller's disappearance captivated the media in the US and around the world. The New York Times ran near-daily updates on the search, which was conducted by helicopters, airplanes, ships, and thousands of locals. After no trace of him was found, the official pronouncement was that he'd drowned. But rumors about the scion's fate have fueled songs, TV shows, novels, countless articles, and even an off-Broadway play. In early February, a documentary called The Search for Michael Rockefeller, a sensationalized, incomplete account based on research done in the early 1970s, will air on Netflix.

Despite insistent denials by the Rockefeller family and the Dutch government over the years, the evidence is abundant and clear, as I discovered while researching my book Savage Harvest: A Tale of Cannibalism, Colonialism and Michael Rockefeller's Tragic Quest for Primitive Art. Rockefeller made it to shore and was killed and ceremonially eaten by the Asmat. Not only that, the Dutch government and the Catholic Church knew and kept it a secret.

Here are the nine reasons I believe cannibals ate Michael Rockefeller:

1) For the Asmat, headhunting and cannibalism were essential sacred practices at the core of their identity

The art Rockefeller was seeking was a sacred byproduct of a complex culture of hunter-gatherers whose sustained contact with the outside world began just a few years before his arrival. Asmat culture was defined by constant warfare with neighboring villages, the taking of heads for initiation ceremonies, and the ritual consumption of the slain. Through cannibalism the Asmat believed they formed an intimate bond with a victim, taking his power, his name, and becoming him.

In their world, no death happened naturally; all death was at the hands of spirits. There was the world of the here and now and the world of Safan, the land beyond the sea. To push the spirits of the dead to Safan, where they could do no harm to the living, required elaborate ceremonies and the carving of beautiful mangrove poles of stacked ancestors up to 20 feet tall called bisj. The poles embodied the spirit of the dead. They carried his name, and were a promise to right the imbalance in the community caused by his death. Only when the poles were complete and a death reciprocated was the ceremony completed, allowing the spirits to move on to Safan and new life flow in the village. And for the Asmat, the proper reciprocation could be achieved by any death, even a woman or child. They were opportunists preferring victims alone, unprotected, and vulnerable. They might wait years for the right moment.

2) The village of Otsjanep existed in a state of profound agitation

At the time of Rockefeller's journey to collect bisj poles and other carvings, Asmat's culture of headhunting and cannibalism was flourishing, even as Dutch officials and Catholic priests were constantly interfering in an effort to end it. Nowhere was that truer than in the village of Otsjanep, a large, powerful, and deeply traditional place of 1,000 souls divided into five jeus, or clans. In December of 1957 the men of Otsjanep and the neighboring village of Omadesep had come to blows. Of 124 who set out for battle, only 11 made it home.

Three months later a zealous Dutch colonial patrol officer named Max Lapre decided to teach Otsjanep a lesson. Lapre arrived in the village with a force of armed policemen and four canoes full of warriors from an enemy village. Although later claiming he only intended to arrest and intimidate the men, his police were armed, and the situation ignited: he shot five men dead and injured a sixth. Even worse, he didn't just kill anyone, but four out of the five jeu leaders, the most important and sacred men in the village.

"The course of affairs is certainly regrettable," Lapre wrote in his official report, "but on the other hand it has become clear to them that headhunting and cannibalism is not much appreciated by a government all but unknown to them … It is highly likely that the people now understand that they would do better not to resist authorities." What of the spirits of those five killed by Lapre? They were out there, wandering around, causing mischief, haunting the village, making people sick. The world was out of balance, an open wound festering in the village every day. The situation was particularly challenging because Lapre was a Westerner and traditional reciprocation was impossible.

3) The details surrounding Rockefeller's accident are well documented

Asmat is 10,000 square miles of flat jungle swamp along the Arafura Sea. Its villages lie up a network of winding, often interconnected rivers. Rockefeller left the village of Per on the morning of November 18th in a small boat with two local Asmat teenagers and Rene Wassing, a 34-year-old anthropologist from the Netherlands New Guinea Department of Native Affairs, bound for the village of Basim. They were crossing the turbulent, three-mile-wide mouth of the Betsj River when the boat's engine was swamped by a wave and the vessel capsized. The two teenagers jumped in the water and swam to shore for help, but Rockefeller and Wassing couldn't see if they made it. The teenagers did make it, but it was close to midnight when they alerted authorities who the next morning scrambled a squadron of P2V Neptune maritime patrol planes with radar sophisticated enough to pick out a floating coconut.

"It is certain that Michael Rockefeller was murdered and eaten by Otsjanep," wrote van Kessel

By that time Rockefeller and Wassing had been drifting for 24 hours and Rockefeller felt impatient. He roped two empty gasoline Gerry cans to his waist, said "I think I can make it," and swam toward shore. Wassing refused to leave the boat and witnessed Rockefeller's departure at about 8 am. Wassing was spotted at 4:30 that afternoon by a Neptune, and rescued the next morning by a boat vectored to coordinates supplied by the airplanes circling overhead. Wassing and the two teenagers spoke widely and at length about the incident. The original Dutch Naval documents detailing the search and rescue, including the latitude and longitude pinpointing where Wassing was spotted on the afternoon of the 19th and his rescue on the 20th, are available. I spoke to the pilot who first spotted the catamaran.

4) We know where Rockefeller came to shore

We know where the boat capsized from Wassing's description. When Wassing watched Rockefeller leave, he said they could still see the shore, even if faintly. The curvature of the earth is listed in routine maritime distance-to-horizon tables: if the mangroves on the flat shoreline were even 50 feet tall, then he and Rockefeller were no more than nine and a half miles from shore - not an unreasonable distance for a fit, determined 23-year-old male to swim in 85-degree sea with a set of ad-hoc water wings. And they might have been closer. At a half mile an hour he was but 20 hours away from shore, an easy romp compared to the 64-year old Diana Nyad's recent 110-mile swim from Cuba to Florida. We know from the searcher's descriptions that the water was calm.

Tides in Asmat are strong and according to the tide charts for that day they were in Rockefeller's favor: between four pm and the next morning, there was a high tide at midnight, a brief low tide at two am and then another high tide at eight am. Which means that for 12 of the 14 hours between four pm and the next morning, the water was pushing him toward the coast when he was most tired. Because we know where the boat overturned and the locations where Wassing was first seen and then rescued the next morning, we know its drift path and speed, which corresponds to prevailing currents - a location and currents that would have placed Rockefeller at the mouth of the Ewta River on the morning of the 20th.

5) Rockefeller swam right into a group of 50 men from Otsjanep

A day's paddle south of the village of Otjsanep stood the government post of Pirimapun, overseen by another Dutch patrol officer named Wim van de Waal. Van de Waal was as different from his colleague Max Lapre as possible. He was 23, craved adventure, loved and felt at ease among the Asmat, traveled widely and unarmed in his district on a boat he'd built himself - the very boat he'd sold to Rockefeller a month earlier and on which Rockefeller had foundered. Today he is alive and well. I found him living in Spain, with vivid memories and a notebook of photos and documents. He let it be known among the Asmat that he'd trade palm building supplies for tobacco, fish hooks, axes - the usual currency at the time. And on the morning of the 19th a group of 50 men from Otsjanep arrived in Pirimapun - they preferred to paddle their canoes down the coast at night, when the tides were right and the waves calm. He bartered with them, they hung around the post all day, and he watched them leave that evening for the trip back to Otsjanep, which lay three miles up the Ewta River. A trip that would place them at the mouth of the Ewta on the morning of the 20th, exactly when and where Rockefeller would have come to shore and where they say they encountered him, according to the Asmat interrogated by investigators.

6) The Dutch government exploited Rockefeller's disappearance for political gain, which helped obscure knowledge of his fate

Rockefeller arrived in New Guinea at a time of geo-political struggle between the Netherlands, the United States, and Indonesia. The Indonesian archipelago, a Dutch colony for 300 years, became independent in 1949 with the exception of the western half of the island of New Guinea. Sukarno, the charismatic nationalist president of the new Republic of Indonesia, insisted that west Papua, too, belonged to his country. Initially the US and the Netherlands, supported by Australia and Britain, were united in their insistence that west Papua remain separate. Sukarno walked a tightrope, however, vacillating between a strengthening Indonesian Communist Party and increased ties to the West, and he was buying hundreds of millions of dollars in weapons from the Soviet Union. In a time of falling dominoes and the fear of a Communist tide sweeping across South East Asia, US president Kennedy broke with the Netherlands and advocated returning west Papua - a place full of nothing but stone age people, his advisors said - to Indonesia as a carrot. The Netherlands responded with the "Luns Plan," named after foreign minister Joseph Luns, which advocated turning west Papua over to the United Nations for ten years, after which it would become an independent country favorable to Dutch and Western interests.

The very week that Rockefeller disappeared, Luns was presenting his plan to the General Assembly and, as New York Governor Nelson Rockefeller flew to Dutch New Guinea the day his son went missing, to be joined by 100 reporters, the Dutch saw an opportunity. "As a consequence of the tragic disappearance of Rockefeller junior, the international press … gives more attention to Dutch New Guinea than the … Dutch proposals in the UN could generate," wrote the Dutch minister of the interior Theo Bott to Luns. "We should turn this to our advantage as much as possible with an eye toward the success of Dutch proposals in the UN." The Luns Plan did not pass, and in 1962 Indonesia took over West Papua.

7) Within a month of his disappearance Rockefeller's fate was known

The villages of Otsjanep and Omadesep lay five miles apart on parallel rivers, each within the territory of two Dutch priests. Soon after the search for Michael ended, Father Hubertus von Peij made his usual rounds. In Omadesep four men with close ties to Otsjanep came to see him and told him that Rockefeller had made it to shore, encountered the group of warriors from Otsjanep resting at the mouth of the Ewta, and been killed and eaten. Their story was detailed. "Where is his head?" asked von Peij. "It hangs in the house of Fin," they said.

"Do not speak of this to anyone from another village," they say about their most sacred stories

Simultaneously, von Peij's colleague Father Cornelius van Kessel heard the same stories out of Otsjanep and investigated. Both priests wrote detailed reports naming names, including who had Michael's skull, his femurs and tibias, and sent their reports to their superiors in the Church and the government. "It is certain that Michael Rockefeller was murdered and eaten by Otsjanep," wrote van Kessel to the local government official in charge of the area. I found their reports in the archives of the Dutch government and the Order of the Sacred Heart brotherhood. Van Kessel, who's dead, left hundreds of pages of unpublished journals as well. Von Peij is alive and living in a home for retired priests in Tilburg, Netherlands and he spoke to me at length about the case. Both priests had been living in the villages for years, spoke the local language, and were certain of Rockefeller's fate.

8) The Dutch government and the Catholic Church acknowledged the reports, took them seriously, and kept their findings secret

The Luns Plan was predicated on the idea that west Papua was a country in the making with a sophisticated elite capable of self-government. In light of this, the priests' reports reverberated in New Guinea and The Hague. In a cable marked "secret" and "destroy" on the very same day the Dutch officially ended the search for Rockefeller, the governor of Dutch New Guinea wrote to the minister of interior: "Resident Merauke received through controller Agats a letter from Father van Kessel in which it is stated that the latter assumes beyond any doubt that Rockefeller was murdered by the inhabitants of Ocanep [sic] village and eaten. It doesn't seem germane to me to give information to the press or Rockefeller Senior at this time. If any questions arise then we could respond to these by stating that the rumor has reached us too and that it will be investigated. This will gain us some time and would enable us in case of confirmation to pick a more favorable moment for publication."

Herman Tillemans, the apostolic vicar in Dutch New Guinea and both von Peij's and van Kessel's boss, wrote: "If you get new information on the case of Rockefeller … be careful, because the topic is like a cabinet of glass. If you find any proof don't mention this to anybody! I really ask you to keep this case strictly confidential in separate letters with a double envelope and the world "secret' on the inner envelope."

In March 1962 the Associated Press published a report that Rockefeller had been killed. The Dutch government denied the report, claiming it had investigated the case already. But that very day, the Dutch dispatched the patrol officer Wim wan de Waal to Otsjanep to begin an official investigation. Van de Waal spent three months in the village and concluded that Rockefeller had in fact made it to shore and been killed.

9) The men accused by van Kessel carried a sacred obligation to act

Over the course of my research I made two trips of two months each to Asmat. I learned to speak Bahasa Indonesian and lived in the villages of Otsjanep and Pirien (Otsjanep split into two villages in 1964) with an elder whose father was named in the original reports. The villages remain remote, with no electricity, plumbing, internet, or stores. I brought with me photos that Rockefeller had shot in the village during his first, brief visit there in June 1961. Elders confirmed that Rockefeller photographed, and therefore met, at least half of the 15 men named in van Kessel's report as having participated in the killing. This is important because the Asmat preferred taking the life of someone they knew, so they could take his name.

The elders also confirmed that the men named in the reports were directly related by blood and marriage to the jeu leaders killed by Max Lapre. Even more importantly, these men had replaced the slain leaders as jeu leaders themselves. They carried a sacred obligation to reciprocate the men killed by Lapre three years earlier. Rockefeller was the first Westerner since Lapre's attack to appear alone, unarmed, exhausted, and vulnerable. At the moment Rockefeller reached the coast after his heroic swim, the son of one of the richest, most powerful man in the world was the least powerful man in Asmat. As Pep drove his spear into Michael's ribs, he was making the world right, reclaiming his Asmat identity and culture. And while all of Asmat tells the story of how the men from Otsjanep killed Rockefeller, the sons of his killers in Otjsanep today refuse to acknowledge any role in the killing. Which is consistent with Asmat culture, since to do so for them would invite retaliation, both physical and spiritual, for a sacred act. "Do not speak of this to anyone from another village," they say about their most important, most sacred stories, because "if you do, you'll die. I'm afraid you will die."

In the end, I found no anomalies. All of the original documents in the Dutch archives matched and corroborated the stories told by the Asmat and the Asmat stories corroborated the 50-year old documents.