PREFACE<br > TO THE REVISED EDITION<br >In the ten years since the publication of the first edition of this book many<br >people--curious laymen as well as specialized students--have found it of value<br >not merely in gaining insight into the problem of race but also in coming to<br >appreciate the intimate relation between group differences and individual<br >differences and the way in which both are related to the genetic system and the<br >biotic program on the one hand and to cultural influences on the other. The<br >literature on race is vast， but there is no other single work that treats the subject<br >in the same way. I have been urged again and again to see that the book remains<br >available for those interested.<br > Because developments since 1970 have made some sections of the original<br >edition out of date， it was decided to rework the text in the light of these<br >advances and to present a revised edition. Although numerous small changes<br >and additions have been made throughout the work， the major alterations are in<br >chapter 3 where recent developments in molecular biology have been incor-<br >porated and in chapter 4 where changes in general attitudes toward intelligence<br >tests and the heritability of the I.Q. required a reworking of the discussion.<br > But the general focus and organization of the book are unchanged and it is<br >hoped that this updated edition may reach an even greater number of the<br >interested and thoughtful.<br >