Evolution is inherently a contextual science. Species are shaped by aspects of their environments that impact survival and reproduction, thanks to heritable variation. Basic scientific research, therefore, begins in the field. Laboratory research must be informed by field research; otherwise, it runs the risk of placing the organism in contexts that make no sense to it, like the proverbial fish out of water.
The human behavioral sciences are often not like this. The bulk of psychological research, for example, takes place in the laboratory with little attention to the context of a person’s everyday life. Scientists from WEIRD (Western, Educated, Industrial, Rich, Democratic) societies study people from their own culture with the implicit assumption that they are representative of all cultures.1 The most field-oriented disciplines, such as sociology and cultural anthropology, have been the slowest to adopt a modern evolutionary perspective.2
There is, however, a cluster of disciplines in the human behavioral sciences that are richly contextual. Some of them originated with the philosophical tradition of Pragmatism in the late 19th century, including figures such as William James and John Dewey, who were inspired directly by Darwin’s theory of evolution.3 John Dewey’s experimental school, which he started at the University of Chicago in 1898, is an example of scientific research that takes place in the context of a school for young children. Behaviorism in psychology is also a contextual science, which studies the behavior of organisms in the context of the history of reinforcement during their lifetimes—although not always in the context of the organism’s cultural or genetic ancestral environment. And fields such as public health, epidemiology, and prevention science are richly contextual at the scale of human populations rather than individuals.4
An appreciation of context in the human behavioral sciences tends to be concentrated in the applied disciplines, where environmental context is difficult to ignore. And the applied disciplines that appreciate context are not well integrated with each other. Finally, none of these disciplines are well integrated with modern evolutionary science, which is only to be expected, since so many of the relevant developments in modern evolutionary science have been very recent.
Against this background, Steven C. Hayes is a towering figure. A clinical psychologist by training, he pioneered a framework for studying human symbolic thought called Relational Frame Theory (RFT)5 and its application in the form of Acceptance and Commitment Therapy and Training (ACT).6 He also helped to found the Association for Contextual Behavioral Science (ACBS), which numbers over 9000 academics and practitioners worldwide. The ACBS website lists nearly 500 randomized control trials7 and over 100 meta-analyses8 demonstrating the efficacy of ACT for a constellation of problem behaviors such as anxiety and depression (associated with therapy) and academic and sports performance (associated with training).
I met Steve in 2009 and we have been working to integrate evolution and contextual behavioral science ever since. Two milestones are a 2014 target article in Behavioral and Brain Sciences titled Evolving the Future: Toward a Science of Intentional Change (with Anthony Biglan and Dennis Embry) and our 2018 edited volume titled Evolution and Contextual Behavioral Science: An Integrated Framework for Understanding, Predicting, and Influencing Behavior. This volume has a novel organization. For six major topic areas (Learning, Symbolic Thought and Communication, Development and Adolescence, Emotions and Empathy, Organizational Development, Behavioral and Physical Health, Small Groups, and Psychopathology and Behavior Change), evolutionary scientists and contextual behavioral scientists wrote separate articles and then met online to compare their approaches, moderated by either Steve or myself. Highlights from the conversations were transcribed for the volume and the full video conversations have recently been made available on TVOL as an important record of integration in progress.
In addition to these contributions to the academic literature, Steve has been instrumental in developing Prosocial, a practical method of working with groups that combines ACT with the core design principles approach the political scientist Elinor Ostrom, who received the Nobel prize in economics in 2009. With fellow contextual behavioral scientist Paul Atkins, we authored the 2019 book Prosocial: Using Evolutionary Science to Build Productive, Equitable, and Collaborative Groups.
The most recent milestone is a 2021 special issue of Clinical Psychology Review, co-edited with Stefan G. Hofmann, titled Integrating Evolution and Clinical Science. As a capstone to the publication of the Evolution and Contextual Behavioral Science conversations on TVOL and to celebrate the special issue of Clinical Psychology Review, Steve and I recorded this conversation on the past, present, and future of the integration that we have worked hard, with many others, to achieve.
Our conversation begins with the story of how our first meeting made Steve cry…
 TVOL articles on this topic include Cultural Anthropology and Cultural Evolution: Tear Down This Wall!, Why Did Sociology Declare Independence from Biology (And Can They Be Reunited), and a series of essays on Evolutionary Science and Sociology.
 A superb book on the philosophical tradition of pragmatism is Louis Menand’s The Metaphysical Club. TVOL articles on Pragmatism include Was Dewey a Darwinian? Yes! Yes! Yes! And Pragmatism and the Third Way of Entrepreneurship.
 This series of TVOL essays by Anthony Biglan titled The Cultural Evolution of Social Pathologies provides contextual explanations for pathologies such as the tobacco industry, the arms industry, the food industry, Big Pharma, Free Market ideology, and the Fossil Fuel industry.
 See this section of the ACBS website for a tutorial on ACT. Hayes’ most recent book on ACT is The Liberated Mind: How to Pivot Toward What Matters.