We are all interested in our roots – our family history. The ability to uncover our personal histories has been greatly enhanced by commercially available DNA testing kits. In Who We Are and How We Got Here, David Reich explains how this urge to know our ancestors has led to the development of technologies to sequence and analyze DNA extracted from the bones of long-dead ancestors, and how this work has revolutionized the study of our species' history.
Reich is a professor of genetics at Harvard Medical School and a Howard Hughes Medical Institute investigator. Over the past two decades, technological advances have enabled scientists like Reich to extract and analyze DNA from ancient bones of our human ancestors, including the bones of Neanderthals and Denisovans. They have used that information to reconstruct the patterns of human migrations and population mixtures throughout history. The results have challenged earlier ideas from archaeology, history, anthropology, and linguistics, leading to a revolution in thinking about human history.
Reich is an intellectual descendant of Luca Cavalli-Sforza and Svante Pääbo. Cavalli-Sforza was a pioneer in the use of genetics to study human history. Using the limited genetic information available to him, he combined it with evidence from archaeology, linguistics, anthropology, history, demography, and statistics to track human migration patterns (Cavalli-Sforza & Cavalli-Sforza, 1995). Although the findings of the ancient DNA revolution described by Reich have supplanted the few major claims made by Cavalli-Sforza, he provided the founding vision for the field he referred to as “genetic geography.” Svante Pääbo, the director of the Max Planck Institute for Evolutionary Anthropology, has been instrumental in developing techniques to sequence the genomes of Neanderthals and Denisovans and, thereby, help realize Cavalli-Sforza's vision. Reich worked with Pääbo on the sequencing of the Neanderthal genome and, with Pääbo's assistance, established the first lab in the United States using whole-genome sequencing to study ancient human DNA.
The main body of Who We Are is divided into three parts. The first deals with what our genomes have to say about the deep history of our species and our relationship to Neanderthals and Denisovans. The largest section of the book, Part 2, “How We Got to Where We Are Today,” details how the advances in genomics and ancient DNA have revolutionized the study of our species' history and provides an overview of what we've learned about that history from our DNA. This is Reich's primary area of expertise, and much of the work described was carried out in his lab. The third part focuses on the implications of the genome revolution for society. In this section the author discusses the implications of this work for our understanding of race, inequality, and human health.
This is a well-written book by one of the leaders in the field of genetic geography; however, I found it a somewhat challenging read due to my ignorance of the details of archaeology and anthropology. But the author provides ample assistance for archaeological neophytes like myself, and anyone who is willing to invest the time with this book will be duly rewarded. The endpapers have a world map showing the locations of 30 events where distinct populations mixed together in the past. Contrary to earlier views, the mixture of distinct populations has been a common event in our species' history, and these events are discussed in greater detail throughout the book. Each of the chapters in sections 1 and 2 begins with a timeline that provides an overview of the period discussed in the chapter. In addition, there are diagrams throughout these sections to highlight key points. The endnotes provide links to the primary literature for those who want to dive deeper.
This is an excellent book that is well worth a read by biology teachers. In addition to offering the reader a better understanding of how genomics is altering our understanding of human genetics and human history, Who We Are also provides insight into the nature of science. Major advances in science are driven by ideas, expressed in such a way that they create a vision that stimulates the curiosity of other scientists and motivates them to search for answers to questions. This is part of the legacy of Luca Cavalli-Sforza. But the early ideas in any field are based on limited evidence, and as technologies improve they enhance scientists' abilities to ask and answer new questions. As a result, the early ideas in a field are often overturned in what Thomas Kuhn (1970) described as scientific revolutions.
Schwab (1962) provided an account of changing ideas in science very similar to Kuhn's. He distinguished between stable and fluid inquiry. Stable inquiry is concerned with filling in the particular details in a growing body of knowledge, while fluid inquiry requires the invention of new conceptions and tests of those conceptions for adequacy and feasibility. Any field of science that is making progress toward a better understanding of its subject will alternate between periods of stable and fluid inquiry. Who We Are describes a period of fluid inquiry in genetic geography, provides an assessment of the current state of the field, and makes predictions about what may be to come. For teachers, the book offers excellent examples of how real scientific inquiry proceeds.