Despite his disgraceful collection practices, Luschan rejected theories that classified some human beings as inferior and remains in high regard among anthropologists. But his work was easily hijacked. The anthropologist Eugen Fischer, a professor of Josef Mengele and a prominent Nazi, also collected Herero skulls; his writings, which have recently resurfaced on white-supremacist Web sites, often cited Luschan. Some skulls that Luschan collected did not reach New York, and were instead absorbed into the Nazi-led Kaiser Wilhelm Institute for Anthropology, Human Heredity, and Eugenics. Many historians believe that when German colonists decimated the Herero and the Nama, they laid a foundation for the Holocaust.

To cover the costs of the Herero bones, Henry Osborn solicited a major donation to the A.M.N.H. from a German-American philanthropist of Jewish descent, Felix Warburg, whose Manhattan mansion now houses the Jewish Museum. Without knowing it, Warburg paid for remains that were taken from the victims of a genocide.

The visit by the Herero descendants was not the first time that the A.M.N.H. had been forced to reckon with the ugly history of its collections. In 1990, Congress passed the Native American Graves Protection and Repatriation Act, or NAGPRA, which required institutions to inventory and repatriate human remains. (NAGPRA applies only to museums that receive federal funding, and does not cover human remains taken from outside the United States.) Researchers at many museums, including the A.M.N.H. and the Smithsonian Institution, opposed its passage. Suzan Harjo, a Cheyenne and Muscogee activist who co-wrote the law, remembers museums arguing that they owned human remains. “What we did was change the conversation from property rights to human rights,” she told me. In the inventory work that followed, one of the names that surfaced was Felix von Luschan. On the island of Lanai, Luschan personally dug up more than eighty Native Hawaiian remains, some of which ended up in the A.M.N.H.

Seven months after the passage of NAGPRA, Edward Halealoha Ayau, an indigenous-rights advocate from Hawaii, visited Ian Tattersall, then the A.M.N.H.’s curator of anthropology, to ask that he comply with federal law and return the Native Hawaiian remains. Ayau says he was shocked to find that Tattersall had simply placed the remains on a tray and covered them with a sheet. “It was so egregious that we kicked him out of his own office, so that we could do our prayers and our ceremony, to apologize to our ancestors for this kind of treatment,” Ayau said. He told me, and others I spoke with agreed, that the A.M.N.H. has since dramatically improved its repatriation practices. “It was very early days in the repatriation process, and frankly, we had not developed normal procedures for dealing with repatriation,” Tattersall told me, adding that he didn’t expect the visit to occur so soon. “In the last thirty years, we’ve learned a great deal, and we now have procedures in place which all parties seem to be pretty happy with.” Still, the museum arguably missed an opportunity, in 1991, to investigate the sources of its von Luschan Collection. If it had done so, it would have discovered, among other grim details, the disturbing context in which its Namibian remains were collected.

Now the museum waits on formal requests from communities of descendants to determine the future of the Namibian remains. Of the Herero descendants I spoke with, all agreed on two things: that the remains of their ancestors must ultimately return to Namibia, and that the neglected history of the Herero and Nama genocide deserves immediate global attention. But the visitors disagreed on one crucial question: More than a century after grave atrocities, how should a community of the living commemorate its dead?

One month after Kavemuii Murangi visited the museum, a delegation of Namibian leaders, including Herero and Nama chiefs, arrived in New York with a different vision for the future of the remains. “Those bones can no longer speak for themselves,” Vekuii Rukoro, a Herero chief, told me. “We need to speak for those bones, and bring out the criminality of what has happened to them.” He wants the museum to put the bones on display, as part of an exhibition on the little-known genocide that decimated his people, helped lay the foundations of the Holocaust, and stocked the shelves of natural-history museums around the world. Namibia has tried a similar approach: in 2011, when Berlin’s Charité hospital repatriated several Herero skulls, they were transported in a casket draped with the Namibian flag and later displayed in a glass case next to a national-liberation monument.

Barnabas Veraa Katuuo, a Namibian-American architect, supports this proposal, and believes that an A.M.N.H. exhibition could empower the Herero in the international fight for recognition. Katuuo is a plaintiff in the American federal lawsuit that aims to hold Germany legally and financially responsible for the genocide. (His attorney, Kenneth McCallion, previously represented Holocaust survivors in a lawsuit against French banks.) “We can’t just bury these remains,” Katuuo told me. “As much as we hate it, we have to do it.” But others disagree just as strongly. “That’s not morally or ethically right,” Jephta Nguherimo, the great-grandson of a Herero genocide survivor, said. “You never see the bones of your loved ones once they’re buried.”

Suzan Harjo told me that museums have used similar disagreements as excuses to delay or prevent repatriation. “We used to get pitted against each other all the time,” she said. Thomas, the A.M.N.H. curator, said that, in this case, the museum will try to identify descendants who have some kind of standing that allows them to represent the wider community. Either outcome—repatriation in the near future or an exhibition—could be possible, he added.

I asked Thomas whether the museum now prohibits research on human remains collected in a context of violence or genocide. “We don’t look at it like that,” he said. When possible, the museum asks descendants what they want, but many scientists didn’t bother to record the specific groups from which they seized remains, so large portions of the collection are unaffiliated. “They are fair game for study,” Thomas said. Murangi told me, “Instead of sitting on these remains until people discover them, they should inform affected communities about human remains in their possession.” Thomas told me that the museum lacks the resources to research the provenance of its entire collection.

In practice, descendants often shoulder the costs, and the years of effort, of locating and repatriating their ancestors one by one. When I called Ayau, the Native Hawaiian advocate, he was in the Seattle airport, accompanying the remains of four individuals on their return journey from Dresden, Germany. Ayau, who is fifty-three, has worked on repatriation cases for more than half his life. He has participated in a hundred and eighteen successful repatriation cases, including fifteen from institutions abroad. In October, the Dresden State Art Collections apologized for collecting, and delaying the return of, Native Hawaiian human remains. “We were healed by it. They were healed by it,” Ayau told me. During the trip, he learned about a separate collection of Native Hawaiian remains, in Berlin. “Here we go again,” he said. “Such is the nature of this work.”

When I sat with Murangi in the park, after the visit to the A.M.N.H. in September, he told me about his great-grandmother, a survivor of the Herero genocide. She rarely spoke about it, he said, and, he thinks he understands why. “She was raped by a German,” he said. When he looks in the mirror, he notices that his skin is lighter than that of many Namibians. “I don’t obsess about my looks, it’s not the struggle that I have. It’s what happened to my people.” After Murangi became a father, decades later, he caught himself avoiding the subject of genocide around his three daughters. “You think about shielding them, so that they do not have to carry the burden of genocide,” he told me. “You just separate yourself from it completely, and put it in a locked box, and say, ‘I don’t want to go there again.’ ”

In October, his twelve-year-old daughter chose to write a middle-school research report about the links between the Holocaust and the Herero and Nama genocide. She insisted on finishing it, even after a photograph of a concentration camp made her cry. “It’s a burden,” Murangi told me. “A burden of memory.” Recently, he decided to tell her about his visit to the American Museum of Natural History, and the boxes of Namibian remains stored on the fifth floor. Her response moved him almost to tears. “I’m very proud of what you’re doing,” she told him. “I think you’re making a difference.”