The premier anthropologist in the country today. –Evolutionary Anthropology on Richard Klein ''High above the western shore of Lake Naivasha, a blue pool on the parched floor of East Africa’s Great Rift Valley, sits a small rockshelter carved into the Mau Escarpment. Maasai pastoralists who once occupied this region in central Kenya called the place Enkapune Ya Muto, or ‘Twilight Cave.’ People have long sought shelter there. The cave’s sediments record important cultural changes during the past few thousand years, including the first local experiments with agriculture and with sheep and goat domestication. Buried more than three meters deep in the sand, silt, and loam at Enkapune Ya Muto, however, lie the traces of an earlier and even more significant event in human prehistory. Tens of thousands of pieces of obsidian, a jet-black volcanic glass, were long ago fashioned into finger-length knives with scalpel-sharp edges, thumbnail-sized scrapers, and other stone tools, made on the spot at an ancient workshop. But what most impressed archeologist Stanley Ambrose were nearly six hundred fragments of ostrich eggshell, including thirteen that had been fashioned into disk-shaped beads about a quarter-inch in diameter. Forty thousand years ago, a person or persons crouched near the mouth of Enkapune Ya Muto to drill holes through angular fragments of ostrich eggshell and to grind the edges of each piece until only a delicate ring remained. Many shell fragments snapped in half under pressure from the stone drill or from the edge-grinding that followed. The craftspeople discarded each broken piece and began again with a fresh fragment of shell. ''Ambrose believes that these ancient beads played a key role in the survival strategy of the craftspeople and their families. In the Kalahari Desert of Botswana, !Kung San hunter-gatherers still practice a system of gift exchange known as hxaro. Certain items, such as food, are readily shared among the !Kung but never exchanged as gifts. The most appropriate gifts for all occasions just happen to be strands of ostrich eggshell beads. The generic word for gift is synonymous with the !Kung word for sewn beadwork. Although the nomadic !Kung carry the barest minimum of personal possessions, they invest considerable time and energy in creating eggshell beads. ''No one knows whether the toolmakers at Enkapune Ya Muto or the other ancient African sites intended their ostrich eggshell beads to be social gifts. But if these beads were invested with symbolic meaning similar to that of beads among the !Kung, then Twilight Cave may record the dawning of modern human behavior.'' –From The Dawn of Human Culture