Science: Unspoiled Primitives

In the jungle valleys, back from the southwest shore of Lake Maracaibo, Venezuela, live the world's most determined isolationists: the celebrated Motilon Indians. They are naked, few in number and disunited. Airplanes fly over their territory; the modern machines of U.S. and British oil companies clank around their borders. But the Motilones, not budging an inch, go right on in the old ways: slipping through the tangled jungle, invisible as the wind, silent as their heavy arrows that can slam through a grown man's chest and out the other side.

Anthropologists are fascinated by the Motilones,...