Medical researchers place a high value on genetic samples from isolated populations because it is easier in such cases to trace the inheritance patterns of particular traits and diseases. For decades, geneticists and paleoanthropologists have gathered samples from people in remote communities in the Brazilian rain forest.

But activists in such communities have often accused researchers of lying to them when the samples were collected — falsely promising, for example, that the samples would be used for only a limited time, or that the samples would be directly used to benefit the community’s health.

American anthropologists collected blood samples from the Yanomami people of Brazil and Venezuela — one of the groups involved in the current dispute — during the 1960s and 1970s, and that effort has led to accusations that the scientists exploited the indigenous group, to turmoil among scientists in the field, to questions about the ethics of such research, and to a complex legal battle. —David Glenn