In the wake of increasingly frequent sightings and two fatalities, the Peruvian government announced last month that it would attempt to help and potentially contact an isolated indigenous tribe that lives deep in the Amazon. But some fear the plan could further jeopardize the group, and on 3 August, the government backtracked on the implications of its announcement, insisting that it would not make the first move toward contact, though it will respond to communication initiated by the tribe.

The case highlights an ongoing international debate about how to best help emerging tribes, who lack immunity to common diseases and are among the most vulnerable people on the planet ( Science , 5 June, p. 1072). “We are extremely worried about this situation and its possible disastrous consequences,” says Francisco Estremadoyro, director of Lima-based ProPurús, a nonprofit that seeks to protect the peoples and the environment in eastern Peru.

Anthropologists and officials are currently most concerned about 30 members of the Mashco Piro tribe in Manú National Park, a remote forested area bordered by the Madre de Dios River. Anthropologists report more than 100 sightings since 2014 of tribe members on the banks of the river. Mashco Piro have raided a nearby village for machetes and goods and killed two villagers, the most recent in May. In the past months they have also repeatedly gestured at, called to, and received goods from local indigenous people across a river; one such contact was captured on video. Tour operators sell tickets for “human safaris” along the river, and missionaries are reported to have given food and clothing to the group in the past year. “You can see a group on the beaches for hours, waiting for the boats to pass call, and request certain products,” writes Luis Felipe Torres, a Peruvian ministry anthropologist who has spent time in the area, in an essay published 22 July. “They are especially interested in bananas, cassava, sugarcane, machetes, and pots.” Torres concludes that “they are deliberately seeking to interact with people transiting the river.”

Given such credible reports, “there are no reasonable grounds to interpret this behavior as a sign that this group wants to remain unconnected to the rest of society,” said Patricia Palacios Balbuena, vice minister in Lima’s Ministry of Culture that oversees tribal affairs, in a 21 July statement. Minister of Culture Diana Alvarez-Calderon subsequently approved a 6-month plan to increase patrols, discourage raids, and make contact “only if they make an appearance and show a willingness for a conversation.” But a ministry official also told reporters that the government planned “controlled contact,” raising concerns about the plan.

When and how to make contact with isolated tribes is a hotly contested issue among anthropologists and groups that aim to protect these vulnerable people. When anthropologists Kim Hill of Arizona State University, Phoenix, and Robert Walker of the University of Missouri, Columbia, proposed in Science (5 June, p. 1061) that “a well-designed contact can be quite safe,” the nonprofit group Survival International in London accused them of promulgating a “dangerous and misleading” idea. Tribes like the Mashco Piro have had limited contact with strangers and foreign pathogens for at least a century, and so are extremely susceptible to illness and exploitation; many newly contacted tribes have been all but wiped out by the flu or other common diseases.

Peruvian policy is to avoid all contact with such tribes and protect them from intruders on their reserves. But in practice, this policy is difficult to carry out. In this case, given the contact that is already occurring, infection is likely, officials say. Hill and Walker wrote in their editorial that leaving groups “exposed to dangerous and uncontrolled interactions with the outside world, is a violation of governmental responsibility.” Balbuena calls for “immediate action by the competent authorities to safeguard their health and prevent negative consequences of uncontrolled contact.”

But Survival International and other groups like ProPurús protested Balbuena’s statement and the vague eight-page plan, fearing that it could set a dangerous precedent that encourages contact. Rebecca Spooner, campaigns officer at Survival International, insists that the desires of the tribe remain unclear. Although tribe members may have sought goods, “shooting arrows at people is a clear indication that they do not want contact.” Therefore, official contact without a request is illegal, she says. Instead, she urges Peru to prevent outsiders from entering the reserves and educate local people about the dangers of interacting with isolated people.

Hill counters that “leaving the Mashco Piro alone will ultimately bring a terrible disaster to them.” He calls the Peruvian government’s intention to act “good news.” But he warns that it will require a commitment extending far longer than 6 months. Tribe members “cannot be left alone, even for a few weeks, during the first 2 to 3 years, or the whole population could go down,” he says.

All agree that the situation is now at a crisis point. “They have reacted far, far too late,” says Spooner of the Peruvian government. She blames the government for failing to keep loggers, missionaries, and tourists out of the Mashco Piros’ land, which she says is at the root of their frequent appearances on the river. Local settled groups that speak a similar dialect report that the tribe faces food shortages, according to Peruvian news reports. And the government report suggests that outsiders are poaching animals like peccary and tapir—staple foods for tribes.

The ministry’s statement on 3 August promises to patrol the river and train local people, and Estremadoyro says officials assured him last week that they do not intend to force contact. Like Hill, he agrees something must be done. But he worries that the government lacks the long-term political and financial support to provide food, shelter, medical help, and other services.

Balbuena says that assisting the Mashco Piro “is a huge challenge that cannot be postponed.” Anthropologists and nongovernmental organizations will be watching closely to see if Peru can help rather than harm members of one of the world’s last isolated tribes.