</p><P> Harvard University Press is proud to announce the re-release of the complete original version of <i>Sociobiology: The New Synthesis</i>--now available in paperback for the first time. When this classic work was first published in 1975, it created a new discipline and started a tumultuous round in the age-old nature versus nurture debate. Although voted by officers and fellows of the international Animal Behavior Society the most important book on animal behavior of all time, <i>Sociobiology</i> is probably more widely known as the object of bitter attacks by social scientists and other scholars who opposed its claim that human social behavior, indeed human nature, has a biological foundation. The controversy surrounding the publication of the book reverberates to the present day.<P>In the introduction to this Twenty-Fifth Anniversary Edition, Edward O. Wilson shows how research in human genetics and neuroscience has strengthened the case for a biological understanding of human nature. Human sociobiology, now often called evolutionary psychology, has in the last quarter of a century emerged as its own field of study, drawing on theory and data from both biology and the social sciences. <P>For its still fresh and beautifully illustrated descriptions of animal societies, and its importance as a crucial step forward in the understanding of human beings, this anniversary edition of <i>Sociobiology: The New Synthesis</i> will be welcomed by a new generation of students and scholars in all branches of learning.