The Dominican Republic is the most visited country in the Caribbean and, according to CNN, the second-happiest place on the planet. However, most of its workers make less than fifteen dollars a day, it has around two million stateless people, and 70 percent of its schools do not offer students safe drinking water. The island is certainly a fascinating place for students to research, so why not take a social justice trip there so they can see it for themselves? That was what Kevin LaMastra had in mind when he took his students to the DR for some snorkeling, horseback riding, and waterfall jumping, but also to check out a garbage dump, a sweatshop, and an HIV/AIDS orphanage. We learn the most when we step outside our comfort zones. Thats not exactly LaMastras sales pitch when hes looking for students to sign up each year, but it becomes the leading philosophy of the trip when he takes them to bond with survivors of Haitis 2010 earthquake, to visit communities hidden deep inside sugarcane fields, and to witness an actual Vodou ceremony.

Some central questions in the natural and social sciences can't be answered by controlled laboratory experiments, often considered to be the hallmark of the scientific method. This impossibility holds for any science concerned with the past. In addition, many manipulative experiments, while possible, would be considered immoral or illegal. One has to devise other methods of observing, describing, and explaining the world. In the historical disciplines, a fruitful approach has been to use natural experiments or the comparative method. This book consists of eight comparative studies drawn from history, archeology, economics, economic history, geography, and political science. The studies cover a spectrum of approaches, ranging from a non-quantitative narrative style in the early chapters to quantitative statistical analyses in the later chapters. The studies range from a simple two-way comparison of Haiti and the Dominican Republic, which share the island of Hispaniola, to comparisons of 81 Pacific islands and 233 areas of India. The societies discussed are contemporary ones, literate societies of recent centuries, and non-literate past societies. Geographically, they include the United States, Mexico, Brazil, western Europe, tropical Africa, India, Siberia, Australia, New Zealand, and other Pacific islands. In an Afterword, the editors discuss how to cope with methodological problems common to these and other natural experiments of history.

In eight case studies by leading scholars in history, archaeology, business, economics, geography, and political science, the authors showcase the “natural experiment” or “comparative method”—well-known in any science concerned with the past—on the discipline of human history. That means, according to the editors, “comparing, preferably quantitatively and aided by statistical analyses, different systems that are similar in many respects, but that differ with respect to the factors whose influence one wishes to study.” The case studies in the book support two overall conclusions about the study of human history: First, historical comparisons have the potential for yielding insights that cannot be extracted from a single case study alone. Second, insofar as is possible, when one proposes a conclusion, one may be able to strengthen one’s conclusion by gathering quantitative evidence (or at least ranking one’s outcomes from big to small), and then by testing the conclusion’s validity statistically.