Justin Barrett
 on August 03, 2021

Making Sense of Evolutionary Psychology

Author of "Thriving with Stone Age Minds," Justin Barrett responds to the reaction some people have to the idea of evolutionary psychology.


The latest book to come out on the series, BioLogos Books on Science and Christianity is Thriving with Stone Age Minds: Evolutionary Psychology, Christian Faith, and the Quest for Human Flourishing, by Justin L. Barrett (with Pamela Ebstyne King). We asked Justin to write about the book, responding particularly to the reaction some people have to evolutionary psychology. We hope this inspires you to buy the book and give it a read!

I recently had an email exchange with an accomplished astrophysicist, who is also deeply engaged with integrating scientific findings with theological positions from his faith tradition. He had listened to my interview on the Language of God podcast concerning my book (with Pamela King) Thriving with Stone Age Minds (2021, InterVarsity Academic) and said he was ordering it immediately, but also admitted that he tends “to be very skeptical of evolutionary ‘explanations’” of human behaviors. My book prominently features evolutionary psychology as a helpful vantage point for re-considering Christian perspectives on human thriving, but I don’t fault my colleague for his skepticism. Perhaps you have also felt this skepticism.

It took me a lot of reading past the more popular treatments, and seeing evolutionary psychological research up close before I warmed to this approach. I am sure that some of my squeamishness was the initial impression that evolutionary psychologists interpret too many behaviors as ultimately about sex. Even setting this appearance aside, most newish scientific claims should be approached with at least some tentativeness and held provisionally. Evolutionary psychology has featured some excesses that have earned it a fairly short leash. As my colleague commented, sometimes it does seem like you can ask about almost any human behavior and you get a very glib evolutionary explanation. Why do men cheat on their spouses? Evolution! Why do women wear make up? Evolution! Why do we love cheesecake? Evolution! Nonetheless, a theoretical perspective or subfield should not be judged by its popular treatments or its missteps but by its total body of work. I can’t summarize all of evolutionary psychology here, but hopefully I can give a better sense of its foundations.

The term “evolutionary psychology” can mean several related things. It can mean studying the evolution of human psychology, often in contrast to the psychology of chimpanzees and other great apes. Why, from an evolutionary perspective, did we come to have the kinds of brains, minds, and behavioral tendencies that we have, instead of some other bag of tricks? We could call this evolution of psychology.

A different “evolutionary psychology” is the study of the thought and behaviors of contemporary humans using insights and assumptions from evolutionary theory.1 This approach may be applied to cognitive, developmental, social, or any other subfield of psychology. Evolutionary psychology of this sort wonders whether particular ways of thinking or behaving may be partially explicable by considering the long-term selection pressures on our species or other features of our species’ history. To illustrate, why do young females typically find themselves attracted to potential spouses from their age and older but males typically look for spouses about their age and younger? An evolutionary perspective would consider the asymmetrical demands that reproduction has on the sexes and the longer fertility that males experience. It may be that each sex has a different mating “strategy” unconsciously working on their mating preferences because such strategies may have been more adaptive than others. An evolutionary psychologist would then look for evidence that these asymmetries placed selection pressure on the psychology of human sexual attraction. They would consider whether alternative explanations capture the available data more completely. This evolutionary psychology is informed by evolution of psychology.

Within evolutionary psychology there are several schools of thought or emphases. One that is sometimes called the “Santa Barbara School” (due to its popularization by Leda Cosmides and John Tooby at the University of California at Santa Barbara2) adds to evolutionary psychology an emphasis on the idea that human minds can be characterized as having lots of specialized subsystems, mental instincts, or “modules.” The idea that humans have some specialized information processing systems (as do other animals) is not a controversial claim, but the number, degree of specialization, and just how (un)receptive such subsystems are to cultural tuning are far from settled questions. Cosmides and Tooby have been such outspoken advocates of evolutionary psychology, that often their approach is thought to characterize all of evolutionary psychology with the result being that those who, for instance, are skeptical about human minds being composed of massive numbers of specialized subsystems, will reject evolutionary psychology in its entirety. Or they will take evidence of the human minds as being importantly tuned up by cultural context as evidence against evolutionary psychology as a whole, but such wholesale rejections are unwarranted.

The logic of evolutionary psychology is fairly straightforward. If we accept the premise that humans evolved over hundreds of thousands of years from some ancestral species that we have in common with all great apes, and accept the claim that evolution works to shape bodies (including brains) and behaviors, then evolution has shaped human brains and behaviors. Because brains facilitate thought, feelings, and behaviors, this shaping of brains by evolution, has also shaped how we think, feel, and behave. Psychological science is the scientific study of thought and behavior, and so a psychological science that ignores evolution, is missing important intellectual resources in doing its job. That is, if we can accept that humans evolved – perhaps this is the mechanism God used to create humans from ancestral species—then, doing evolutionary psychology is part of doing thorough psychological science.

But does an evolutionary perspective add any explanatory power? Even if one is prepared to accept the basic argument for an evolutionary psychology, it may be that humans have been gifted with minds that are so good at learning new things about new environments that there is no reason to bring our species’ prehistory into the discussion. Instead of lots of mental instincts (modules, subsystems, etc.), we have a super-powerful, super-flexible, all-purpose learning system. And so, anything interesting to say about human psychology is a product of experiences in this lifetime, not the accumulated baggage of ancestral experiences. Perhaps. But notice that this sort of position should be the conclusion of psychological science, not the default stance. What such a position seems to be claiming is that humans are the only known animal on earth to not have brains, minds, and behaviors that have been tuned to specific fitness demands through evolution. Such a prima facie improbable claim requires considerable evidence.

And the evidence just isn’t there. It is easy to generate examples of domains in which humans show fitness-relevant information-processing predilections. We don’t process any and all information in our environments, and we don’t process that information in some kind of neutral manner. Rather, we selectively attend to and process information in ways important for our type of animal. To take two examples that I mention in the book: (1) infants readily form fear associations with snakes, not snails or sneakers; and (2) essentially from birth they selectively attend to human faces among all of the visual stimuli around them. These information processing “biases” (as we call them in psychological science) are the default tendencies of our psychology. I mention many others in the book.

It is common for evolutionary psychologists to draw upon evidence from infant/child developmental, neuroscientific, cross-cultural, experimental, cross-species, and computer modeling studies. Evidence from studies of these sorts point to many ways in which humans—just like any other animal that has been studied—have specialized ways of thinking, feeling, and acting in response to different sorts of things in their environment, many of which appear to be ancient adaptations.

Many very good recent books, such as those by Kevin Laland and Joseph Henrich3, seem to argue that human specialness is not found in our mental instincts but in our ability to learn from each other, teach each other, and otherwise adapt to our environments. I agree that human cultural learning is remarkable and unparalleled on earth. Perhaps these capacities are what sets humans apart. It does not follow, however, that human minds are best characterized as bland sponges that passively soak up whatever is around them. Indeed, Laland and Henrich both identify some of the very unusual psychological abilities that enable cultural learning—most of which are either only present in humans or greatly enhanced in humans. We have to do things like selectively attend to others (especially eye gaze), figure out what others are attending to, speculate about what it is they want to communicate to us, and so on. These are precisely those evolved capacities that evolutionary psychologists are interested in understanding better.4

Just because humans are usual in their abilities to learn and adapt, it does not follow that somehow our basic psychological endowment isn’t importantly constrained by ancestral fitness demands, much like other animals. That we carry in our psychology the imprints of evolution working on our ancestors is what is meant by saying humans have “stone-aged minds.” Evolution works slowly on the basic biological endowment, and genetic evidence suggests we have not changed much genetically in some 200,000 years. Hence, our species has spent at least twenty-times as long living in stone-aged environments (i.e., living with only the ability to make stone, wooden, and fiber technologies, and not bronze or iron, etc.). Furthermore, the Stone Age only ended for a small minority of humans about 4500 years ago—not enough time for massive changes in our natural endowment. Indeed, depending upon one’s criteria for what counts as a full transition out of a “stone-aged” culture, there are still stone-aged societies today. And so, humans really can be said to be trying to thrive in a contemporary world with stone-aged minds. This mismatch between our nature and our environmental niche—a gap rapidly enlarged by the industrial and high-tech revolutions—is one of the great obstacles we face when trying to live the abundant lives God wants us to enjoy.

I understand being suspicious of evolutionary psychology. Sometimes its practitioners seem to over-interpret their studies and find adaptations where there might be evolutionary byproducts, drift, or deliberate innovation. But if you think it is possible that God used an evolutionary process to bring about humans, I encourage you to give evolutionary psychology a fair chance. In addition to reading my book, check out some of the books and articles that I have noted here, keeping in mind that these books are summaries and interpretations of the available evidence and do not detail all of the relevant studies for the claims made. To get a better feel for the kind of evidence that backs the claims, check out some of the research reports and review papers cited in the books. Michael Tomasello’s website is a rich resource for basic research articles and a number of videos from his studies with chimpanzees and children. Spending some time there is a great way to get a sense for the depth and variety of research that just one evolutionary psychology lab group has produced.5 For videos, podcasts, and readings that my team and I have designed especially for theologically-minded people, check out the TheoPsych Academy.6 Applications from evolutionary psychology are sprinkled throughout but especially in the “On Human Nature”course.

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About the author

Justin Barrett

Justin Barrett

Justin L. Barrett (PhD Cornell University) is President of Blueprint 1543 and honorary Professor of Theology and the Sciences at St Andrews University School of Divinity. Prior to founding BP1543, he was at Fuller Theological Seminary, where he led the Thrive Center for Human Development and then the Office for Science, Theology, and Religion (STAR). He came to Fuller from the University of Oxford, where he taught and served as senior researcher for Oxford’s Centre for Anthropology and Mind. He has also taught at the University of Michigan and Calvin College, and served as co-area director for Young Life in Lawrence, Kansas. His book Thriving with Stone Age Minds: Evolutionary Psychology, Christian Faith, and the Quest for Human Flourishing, co-authored with Pamela Ebstyne King, is out now as part of the BioLogos series of books on science and Christianity. Some of his other publications include Psychology of Religion (ed., 2010), Why Would Anyone Believe in God? (2004), Cognitive Science, Religion, and Theology: From Human Minds to Divine Minds (2011), and Born Believers: The Science of Children’s Religious Belief (2012).