["Under the Mountain Wall," a] sensitively written book by Peter Matthiessen, is an engrossing human document that sheds light on the story of man, stone-age or modern. The material is drawn from the 1961 Peabody-Harvard Expedition to Central New Guinea whose members—Matthiessen was one—were the first white men ever to establish close contact with the Kurelu and live among them for several months….

In the world today there are very few men left who could truly be called "stone age" in the sense of being completely untouched by the faint echoes emanating from the larger world beyond their borders. The Kurelu of Central New Guinea, dwelling in the mile-high Baliem Valley, were such a people. Matthiessen, in his Preface, speaks of them as destined to be no more than another backward group "crouched in the long shadow of the white man." Ironically, so fast-paced are present changes...