Olduvai Gorge is one of the most important prehistoric sites in the world and has been instrumental in furthering understanding of early human evolution. Chasing a fancy butterfly in the green wilds of Tanganyika 50 years ago, a German entomologist named (Wilhelm) Kattwinkel tumbled off a rocky ledge and nearly killed himself. When he regained his senses, he found himself in an anthropologist's dream world: an erosion-created rift with layer after layer of fossils, bones and ancient artifacts. The find was named Olduvai Gorge, and Kattwinkel's heirs ever since have been scrambling up and down its sun-baked sides in search of clues to man's earliest awakening. ("Time", Friday 10 March 1961) 