Preface

All of us alive today owe our very existences to the many layers of migration undertaken by our remote ancestors, going back far into time, even beyond the rise of humanity itself to the prehuman beginnings of life on earth. Working hand in hand with the processes of evolution, migration has spread the evolutionary products of biological mutation and cultural innovation to all regions where humans exist. Our genes, our languages, our systems of food production and technology, all exist in part because of migration. I emphasize in part, because migration cannot be seen in its own right as a biological or cultural cause of mutation or innovation. But as a mechanism of spread, it often meant that internally generated mutations and cultural innovations in the broadest senses could find new and fertile ground and proliferate to a degree unthinkable if the carriers all stayed at home. If all our ancestors had remained immobile, we simply would not exist as the environmentally demanding and dominating species that we have become today

This book is about migration in all periods of human prehistory, from the initial spread of hominins out of Africa about two million years ago, down to the continental migrations of agricultural populations within the past 10,000 years. In general, I draw the line when history starts, so the Huns, Goths, Mongols, Conquistadores, and Victorians do not feature. We know something about them from history, even if the history is sometimes rather thin. On the other hand, some nonliterate peoples migrated over huge distances very recently in time, even contemporary with the European Middle Ages, but they did so in their own fully prehistoric circumstances. The Bantu-speaking peoples in Africa, the Eastern Polynesians, and the Inuit of the North American Arctic were all migrating as Gothic cathedrals arose in Europe, therefore they people the following pages.

As I was writing this book, an invitation from Immanuel Ness in New York gave me the opportunity to edit Volume 1 (Prehistory) of the Encyclopedia of Global Human

Migration (Ness and Bellwood 2013), an opportunity that allowed me to select and invite as authors some of the world's foremost scholars in the prehistoric sciences of archaeology, human biology and comparative linguistics. One of the developments that surprised me during the editing of this volume was the increased importance given in so many disciplines to processes of migration in human affairs, both ancient and modern. When I was a student of archaeology in the 1960s, migration was becoming an uncomfortable concept for many archaeologists, and home-grown independence or multiregionalism was becoming the favored perspective on the past in both human evolution and archaeology. The very different modern view of the 2010s reflects the huge advances in the biological sciences in recent years, especially in genetics, since DNA research now makes it very obvious that migration has always been of great significance. Before the 1970s, archaeologists and comparative linguists could not easily demonstrate the reality of migration without direct historical evidence, and neither indeed could geneticists at that time. Spreading cultures and languages in themselves are not automatic evidence for actual population migration, as opposed to cultural diffusion, although they can be argued to have been so in specific circumstances.

As with modern migration, prehistoric migration always needed a reason. One very common reason in many situations was growth in the size of the human population. A group of prehistoric humans living in complete demographic and environmental equilibrium would never have needed to move, unless the environment changed in an adverse way or the average couple switched to having more than two children. As we all know, human life has never existed in such idyllic circumstances, neither in the past nor in the present. Populations can grow in numbers, new land can be required, resources can diminish for many environmental and human-impact reasons, enemies can attack and force people to flee and not return, utopias can beckon. Circumstances can induce a group of humans to spread or migrate, whether consciously or unconsciously, by choice and group agreement, or simply through a less conscious transgenerational success in procreation.

In some ways, this book is a sequel to my earlier First Farmers, published by Blackwell in 2005, except that here I cover hunter-gatherers as well as farmers and go back much further in time to the beginnings of the genus Homo over two million years ago. The chapters are arranged partly in chronological order and partly in geographical order, but the main separation is into hunter-gatherer migrations (Chapters 3-5) and agriculturalist migrations (Chapters 6-9). I commence with two comparative chapters (1 and 2) on migration as a process of human movement and on how the multidisciplinary evidence for it might be perceived and interpreted by prehistorians, these being scientists from many disciplines (not just archaeology) who strive to understand the human past prior to the beginnings of written records.

The writing of this book has been a challenge for me because of the great breadth of information that I have had to collect. I have realized, over many years of research, that simply trying to interpret prehistory from a viewpoint of archaeology, or comparative linguistics, or genetics, or any other discipline alone is really rather a pointless exercise and one that can lead to a remarkable narrowness of perspective, not to Mention time-wasting errors that can penetrate the literature and then echo down through the years. Overall, I have found the collection of multidisciplinary data to be an immensely energetic and stimulating exercise, given the phenomenal rates of publication in newly developing scientific disciplines, and genetics in particular. I stopped reading in February 2013, and any revolutionary observation published since then will not have made these pages.