In this first volume I have tried to set out the present state of our knowledge of the background evidence, against which the very important fossil human remains from Olduvai and the Stone Age cultural sequence there can be assessed. Preliminary reports upon the fossil hominid discoveries have appeared from time to time since 1958, both in Nature and in the popular press, and scientists are therefore already aware of the general picture. The study of the fossil human remains and of the stone tools, together with a detailed report upon the excavations of sites will appear in subsequent volumes.

Volume 2 by Professor Phillip V. Tobias, of the Medical School, Johannesburg, is now in the final stages of preparation, and will be published during 1967. It deals with the skull of Zinjanthropus boisei in very considerable detail.

Three further volumes are in preparation. Mrs M. D. Leakey's deals with the living sites and cultural sequence of Bed I and Bed II, and will include chapters by Dr Leakey on the fauna associated with each living floor.

Dr Richard Hay's volume, dealing with the details of the geology of Olduvai Gorge, is being prepared.

Another volume by Professor Phillip Tobias, also now in active preparation, will be a careful study of Homo habilis, the LLK skull, and a variety of other Olduvai hominids.

At the time of writing this report, i.e. up to the end of December 1961, fossil hominid remains had been found at three different levels in Bed I.