Educated at Henderson County High School, he had a biology teacher, Mr. Ned Barra, who encouraged his interest in insects.
Arriving in Brazil in 1976, Posey made lasting friendships with researchers at the Museu Paraense Emílio Goeldi, in Belém, and the Instituto Nacional de Pesquisas da Amazônia, in Manaus.
After his graduate studies, Posey returned to Brazil in 1982, as a professor in the Department of Biology at the Federal University of Maranhão in São Luís, then reorganized under the chairmanship of geneticist Dr. Warwick E. Kerr.
Although the term "ethnobiology" had been used in the past for a different idea, Posey adopted this for his study of indigenous and folk knowledge about plants, animals, and ecosystems.
Posey repudiated this view and dared to see indigenous and folk societies as the inheritors of a vast corpus of useful knowledge for the sustainable utilization and management of natural resources.
As can be seen in his review of Diamond's best-seller Guns, Germs and Steel: The Fates of Human Societies in 1999, Posey would have biological determinism laid to rest.
In his activism, Posey incurred opposition not only from those who would exploit natural resources belonging to Indians but also from scientists and academics who were callous in their disregard for indigenous intellectual property rights.
Posey's support for indigenous peoples brought him into conflict with the Brazilian government in 1987, when Paiakan and Kube-l, two young Kayapó leaders he was accompanying in Washington, D.C., complained to World Bank officials of a planned hydro-electric dam on the Xingu River that would flood Indian lands.
The threat of criminal prosecution from the federal government against Posey and the Kayapó chiefs, for interfering in Brazilian foreign affairs, caused a public outcry both in Brazil and abroad.
Posey questioned whether scientific research, even of the most disinterested sort, might not lead to the violation of indigenous intellectual property rights or bio-piracy.
Major concerns outlined by conference contributors were the study of the ways that indigenous and rural populations uniquely perceive, utilize, and manage their natural resources and the development of programs that will guarantee the preservation of vital biological and cultural diversity.
The International Society of Ethnobiology (ISE) created the "ISE Darrel Posey Fellowship for Ethnoecology and Traditional Resource Rights" in order to "promote understanding of peoples' complex and dynamic relationship with their environment, and supports indigenous peoples and local communities working to sustainably manage, and security rights to, their environments and resources.
This session celebrated Darrell Posey's many contributions and influences in the field of ethnobiology over the past several decades, both direct and indirect.
[5] When Western scientists and other academics listen respectfully and learn at the feet of indigenous and traditional leaders, Posey's legacy will become reality.
Following his death, Posey's executors donated a large collection of photographs and other papers relating to his Kayapó research to the Pitt Rivers Museum, University of Oxford.