For 99 percent of our time on earth, mankind has lived by hunting animals and gathering anything edible the vegetation provided. Only in the last 10,000 years have men cultivated crops and lived in settlements. Today just a few human remnants still live as hunters and gatherers.

Their inevitable passing may deny us acquaintance with our contemporary ancestors and a window into the past providing insight into who we were and where we came from. Some study primitive cultures because they are dissatisfied with our own, others because they see patterns that assured survival. Whatever the motive, we might ask if there's not a lesson to be learned-before the way of life chronicled in "Namkwa" vanishes.

Among the few remaining hunter-gatherers are the Bushmen of the Kalahari Desert in Namibia and Botswana, a wasteland of thirst and thorns. Taller than pygmies, but at an average height of 5 feet, much shorter than the Bantu, the Bushment and their Khoisan cousins, the Hottentots are the survivors of a race believed to have once inhabited much of Africa. With their high cheekbones, eyefold, and yellow skin color, they look oddly Mongoloid. Over thousands of years they have evolved a way of life perfectly adapted to one of the world's harshest environments.

With poisoned arrows, superb tracking skills, and remarkable stamina, the Bushmen bring down gemsbok and springhare. With digging sticks and encyclopedic knowledge of the Kalahari plant life, they are able to find every nut, fruit, berry, root and tuber the desert provides. Though their clothing consists of little more than jackal skins and ostrich shell beads, they are able to endure great extremes of heat and cold, sheltered only by depressions scooped in the sand and a lean-to windbreak. They have a simple tool kit, and make their world out of next to nothing-athumb piano, rattles for dancing, stories and songs. There are perhaps 25,000 Bushmen left, some now working as farmhands or cattle herders on Tswana ranches, some still living off the veld.

As Margaret Mead says in her foreword to "Namkwa," "This book is a unique story of one of the more romantic episodes in the history of the encounters between a European scientist and a primitive people." Heinz is a middle-aged, German-born, Dart-mouth-educated parasitologist who became intensely involved with the Xko, and came to be regarded as at least a half Bushman. For 15 years beginning in 1961, he divided his time between teaching at the medicial school of the University of Witwatersrand, and his life in the Kalahari. While not exactly Henderson the Rain King, Heinz is frank to admit that he went to the veld after a bout with the psychiatrist and his second failed marriage. He went to escape his personal problems, but ended up in a love affair with a group-and a woman.

His growing affection for the Xko, and for Namkwa, may have surprised even Heinz. His marriage to Namkwa began as an exploitative liaison-a sexual and housekeeping convenience. But her intelligence and strength of character bridged a profound cultural gap and survived long periods of separation. Int the beginning, Heinz rationalized his affair with Namkwa and the group as scientific research, and he has published useful anthropological work. But his approach was intensely personal; he chose to learn about the Bushmen by becoming one. He shared their life in every way-was initiated into the tribe, became one of the best hunters, learned the five-click language, and respected their taboos. He ended up their de facto headman, attempting to take charge of their lives.

Heinz recognized that the traditional way of life was changing even as he watched it. Government officials proposed a reservation to isolate the Xko from these forces. But Heinz saw "his" people not as specimens in a zoo, but as helpless humans confronting a power over which they had no control. Change was inevitable, but he hoped that he, with Namkwa's leadership, could be an agent of change-for-the-better. That his plans went awry suggests that intervention is not as simple as it seems. Inevitably there were conflicting ideas about what is best, and who's sincere. And like many liberal white South Africans, Heinz reveals a strong streak of paternalism.

Yet through his experience one comes to know the clever and progressive Namkwa, greedy Gruxa, lecherous Thamae. Unfortunately, the book is disappointing because the presentation is disjointed and the writing often clumsy. It's much more accurate than the poetic posturings of Laurens Van Der Post's "Lost World of the Kalahari," but not nearly so informative or well written as Elizabeth Marshall Thomas' "The Harmless People." And scholars will rely on the work of Lorna Marshall, or the forth-coming study by Richard Lee. Ultimately it's impossible to judge "Namkwa" without making some judgment of Heinz himself: time and again his ego and 19th-century Teutonic romanticism intrude. His co-author sums it up in the afterword: "His eccentricity took him into a unique situation, his strength made it productive, his ego and vulnerability added drama, and the sum total of circumstances took it close to tragedy . . . This book is a record of a man's infatuation with a Kalahari way of life, his growing attachment to a pre-literate, Stone Age people and particularly his love for a Bushwoman."