The Secret of Our Success is an ambitious and timely endeavor to reframe the conversation around human behavior. Rather than viewing the history of our species as a linear progression—one in which culture emerged from genetic evolution and then took over—The Secret of Our Success treats culture, biology, and behavior as deeply intertwined concepts that function iteratively to make us the dominant species on the earth today.
Joseph Henrich’s background in anthropology, human evolution, and psychology makes him adept at integrating current theories and research in human behavior from diverse perspectives. The Secret of Our Success offers evidence for gene-culture coevolution from a range of departments and methodologies—from the laboratories of developmental psychologists to Henrich’s own ethnographic work with small hunter-gatherer societies. Such an approach both lends credibility to Henrich’s thesis and provides fruitful avenues for future interdisciplinary research. By comingling theories from biology and the social sciences, Henrich highlights just how outdated the “nature versus nurture” approach to human behavior has become.
The book is structured with two main goals in mind. First, Henrich seeks to recast culture’s role in human evolutionary history. To do this, Henrich problematizes popular notions about the pathways that led to the dominance of our species relative to others. It is not our intelligence or cognitive flexibility that gives humans the upper hand but our unique ability to accumulate and integrate knowledge from one another over time, thus creating a “collective brain” of innovative solutions to adaptive problems. In turn, the advantages conveyed by cultural transmission select for better and better cultural learners, creating the phenomenon that Henrich refers to as “gene-culture coevolution.”
This first point is bolstered by evidence of specific psychological adaptations that underlie cultural learning, such as our almost compulsive desire to mimic the behavior of successful individuals, and examples of cultural practices that may have helped shape our genetic makeup. For instance, genes associated with lactase persistence (the ability to consume milk into adulthood) are present in over 90% of indigenous populations from Scandinavia and the British Isles, whereas they are present in only 20% of individuals from the southern parts of India. What explains this difference? Henrich points out that areas where lactase persistence is high correspond with areas that have a long history of domesticating livestock. While originally useful for meat and hide, the presence of these animals in society likely created a selection pressure that favored individuals who could use their milk as a source of nutrition. As Henrich notes, “Once cultural evolution creates the selection pressures, natural selection often manages to find and favor several different genetic variants to address the challenge” (p. 92).
Second, Henrich introduces evidence that culture not only interacts with our species’ genetics, it also shapes brain development over the course of a person’s life. This theory is supported by several striking examples, including psychological experiments that demonstrate a connection between visual perception and culture. For example, in Chapter 14, “Enculturated Brains and Honorable Hormones” the reader is presented with the striking example of how Western and Eastern culture can impact perceptions of physical objects. When presented with images of drawn lines and asked to assess their length, Westerners—who have a long history of viewing society from the perspective of the individual—show more aptitude for determining absolute length. Meanwhile, those who were raised in Eastern cultures—which tend to focus more on the collective/relational aspects of society—excelled at assessing the relative lengths of lines. This second point is perhaps the most important and novel argument in the book since it implies “that people who experience very different institutions, technologies, and religions …will be both psychologically and biologically different, even if they are not genetically different” (p. 327). Or, put more bluntly, “we often treat cultural differences as if they were nonbiological and nonmaterial, almost otherworldly. This confusion emerges when people think that showing something is ‘in the brain’ or driven by hormones means it’s genetic. This is not the case” (p. 263).
The layout of The Secret of Our Success makes it easy to jump to different chapters without having to read the book linearly, depending on one’s familiarity with the topic. The first few chapters offer a solid introduction to competing theories regarding the evolutionary success of humans vis-à-vis other species. In addition to offering colorful examples of explorers stranded in unfamiliar territory, the beginning of the book will help readers understand culture from the perspective of cognitive psychology and evolutionary biology. The middle of the book demonstrates the breadth of areas to which the gene-culture coevolution theory can be applied, from understanding the origins of faith to reconceptualizing genetic differences among populations. The end of the book dives back into the world of psychology, demonstrating how culture can shape the very foundations of how we as people perceive and interact with the world around us. These later chapters will be the most valuable to those seeking a career in academia, since they offer a sneak peek at the paradigm shift that is taking place in the social sciences.
The style of Henrich’s prose is in line with many popular psychology books today (e.g., Blink, The Better Angels of Our Nature, etc.). This should not discourage serious students of human behavior from reading the book. Rather, the style allows for a relaxing introduction to a complex topic. In fact, this book will be best appreciated by those with at least an undergraduate understanding of evolutionary biology and genetics, since Henrich uses theories from these fields with little introduction to their basic concepts. When Henrich does present basic introductions to theories, they tend to be from the fields of psychology and neuroscience. This makes The Secret of Our Success an ideal book for graduate students looking for inspiration or those who are curious about the direction of cutting-edge research in human behavior. Conversely, the book’s lack of technical jargon, entertaining examples, and fluid narrative mean that audiences of all levels will, at the very least, find the book thought-provoking and entertaining.
While it is a must-read for anyone interested in the future of the social sciences, the book is not without its flaws. At times, the book can feel redundant, and readers who are already familiar with the topic may find themselves skimming chapters that seem specifically designed to overload nay-sayers with as many examples as possible. There is little doubt that Henrich’s goal is to sell the reader on the theory of gene-culture coevolution. As a result, the book sidesteps many of the criticisms surrounding group selection, a concept that he employs (though not in name) to help explain early emergence of culture in our species. This is unfortunate because a more direct response to critics of his theory would have given the book more depth and relevance to advanced readers. Furthermore, Henrich omits any mention of eusociality, an intriguing phenomenon that has received much attention in evolutionary biology for its ability to shift evolutionary pressure from the individual to the group, thus causing multiple organisms to behave more like a single superorganism. This omission is odd given Henrich’s observation that culture may be driving humans in a similar, though not identical, direction. Despite these drawbacks, this work undoubtedly will play an important role in conversations about human behavior for years to come. It should be recommended reading for a wide variety of audiences.
