In the past, my history columns have mainly concerned about the last 120 years. This column will deal with the approximately 3.5 billion years since life began, because I think all psychologists need to think about that, too. I have been working on a “Darwin project” for about a year and a half now and have read over 200 books on the history of the field of evolution and human behavior. This essay gives me a chance to try to pull some of this material together in a brief way. In addition to the great achievements of humanity—art, music, language, technology, and science itself—which are all illuminated by Darwin’s theory of evolution, his work and that of his followers have also shed considerable light on topics closer to the hearts of clinical psychologists, such as ADHD, aging, aggression, alcoholism, anxiety, attachment, autism, depression, problems in neurodevelopment, intellectual disability, language impairment, perceptual disorders, and schizophrenia. Obviously, this paper cannot cover this whole spectrum of human misery. It does attempt to show the clear applicability of Darwin’s theory to problems such as depression and anxiety.
Charles Darwin himself grew up in an environment where clinical issues were salient. His grandfather, Erasmus Darwin, was a physician who wrote a noteworthy poem about his own concept of evolution. Charles Darwin’s father, Robert, was also a physician and encouraged his son to choose the same profession, and he did indeed attend medical school at the University of Edinburgh. As it turned out, he was too tender hearted to perform even minor surgical procedures, so he went on to Cambridge and prepared to be a clergyman (!) before he decided on the life of a naturalist. Personal health issues provoked in him an interest in clinical matters. He suffered from a mysterious gastrointestinal illness much of his life. It has been debated whether this was a form of Chagas disease acquired in South America or was psychosomatic. The illness was never cured despite considerable efforts by the “hydrotherapists” of that day.
Darwin’s famous book, On the Origin of Species, published in 1859, sold out immediately and set off a firestorm of both advocacy and criticism from his fellow scientists. Another influential author in this era was Herbert Spencer, the man whose psychology was the best known in Darwin’s time. Spencer’s writings concerning evolution were published in 1857, two years before Darwin’s. Spencer invented the phrase, “survival of the fittest,” which Darwin adopted. Already in the 1870s, Spencer’s work was labeled as “social Darwinism.” As a result of Richard Hofstadter’s writings in the 1930s, Spencer became widely known by this phrase. By the 1940s Hofstadter’s work had given social Darwinism a bad name in the social sciences, which has to some extent lingered on to the present. Spencer was somewhat inaccurately portrayed as having views resembling those of “robber barons” such as Rockefeller or modern libertarians and advocating a total absence of any social safety net. Actually, Spencer only opposed the use of government assistance to the poor on the grounds that it might create a dependent class. He approved of private charity. In 1871, Darwin published his own account of the evolutionary descent of humans, including his ideas about sexual selection.
The most influential modern psychologist who took Darwin seriously was William James, whose psychological writings in the 1870s already were noteworthy and arguably established him as the founder of psychology in America. His textbook, commissioned in 1878 and published in 1890, has been read by generations of psychologists and is still in print. Ever since that time his work has influenced us toward accepting the scientific theory proclaimed by Darwin. James was a graduate of Harvard Medical School, though he never practiced medicine, because he, like Darwin, was subject to considerable psychological stress and wrote about clinical matters with personal conviction as well as great authority. The essence of Darwin’s theory is that humans, like other organisms, evolved over a period of what he underestimated as 400 million years or less. This occurred through a process of “natural selection” in which the hereditary characteristics of those organisms that survived and produced offspring were preserved in their progeny. Organisms that did not manage to reproduce obviously did not pass along hereditary characteristics (what we now call “genes”) to later generations. Primates with larger brains were highly adaptable to a huge variety of different environments. In this way, humans have indeed acquired impressive dominion over the earth.
Another process specified by Darwin was “sexual selection” in which preferences of mates determined which hereditary characteristics survived in offspring. Peahens prefer peacocks with those beautiful tail feathers we all admire; the peacock’s tail therefore survived despite the fact that it was also attractive to potential predators. Women likewise prefer men who are physically attractive, intelligent, assertive, and high in social status; men prefer women who have “beautiful” faces (including those that are particularly symmetrical) and figures, are healthy, compassionate, and seem likely to be able to bear children. This is true despite the fact that “beauty,” like the peacock’s tail, is not necessarily of direct functional value. Obviously, there are also cultural variations in mate preferences that go beyond any inherited ones. For example, in certain third world countries, women are more likely to select men who are good hunters; men are more likely to find women attractive who in our own society might be seen as obese.
Evolutionary psychologists distinguish between “proximal” and “ultimate” causes.
Psychologists, including clinical psychologists, have been mostly concerned with proximal influences, namely those resulting from the person’s current environment. These include learning, the influence of parents and peers, and, of course, psychotherapy. Darwin and his followers are more concerned with ultimate causes such as evolved adaptations, perhaps acquired in the Pleistocene era of geological time, which lasted from 2,588,000 to 11,700 years ago. Many animals other than humans are “precocial,” requiring little or no parental care. They tend to have relatively short life spans. Humans are “altricial,” requiring a lot of parental care and indeed support from their communities. They also live a relatively long time. Humans have large brains and therefore large heads. Theory speaks of “neoteny,” the idea that birth of immature offspring allows for greater behavioral plasticity. Newborns also have skulls with bones that are not fully knitted together so that they are able to pass through the birth canal. Human infants are thus less developed than the young of most other animals, and much of their brain growth must be post-natal. Humans therefore experience a long and complex period of dependency usually on parents or “alloparents” in communities where many others take on a parental role. The transition from dependence to independence experienced by young adults often involves so much anxiety and depression that they seek professional help. Therapists might find understanding the evolutionary context of these and other emotions to be useful. This may be the price we pay for our large brains.
One of the most ancient psychological problems is that of depression. The Hippocratic writings spoke of “melancholia.” They suggest that this was due to an excess of “black bile” in the body and advised that it be treated by purging, perhaps using enemas, and this theory persisted up to the time of 17th century French dramatist Moliere and beyond. Clinical psychologists commonly attribute depressed mood to life events such as death of spouse, divorce, marital separation, and imprisonment. These are, of course, items on the Holmes and Rahe Social Readjustment Rating Scale and all represent good examples of proximal causes. Without in any way denigrating the importance of such influences, a Darwinian clinical psychologist would also wonder about ultimate causes. For example, it may be that ancestral primates who lost their mates and underwent a time of depressed mood and reduced activity elicited sympathy and practical help from their peers in obtaining food and raising children. If so, those who suffered such “problems” might actually adapt better than others less subject to depression, in the sense of being more likely to survive and to produce additional offspring. In addition, there has been recent talk of depression (and anxiety) as responses to social exclusion.
Third, an influential theory has emerged over the last few decades that links depression to infectious disease. When a person becomes ill, for example with influenza, the immune system reacts by producing hormones known as cytokines such as interleukin 1, interleukin 2, interleukin 6, and tumor necrosis factor (TNF). Some of these cytokines have been used to treat cancer, and it has been found that they lead patients to experience malaise, withdraw from social activities, sleep excessively, and cease to enjoy many of their usual activities (anhedonia), in other words, mild symptoms of depression. When cytokines are administered to laboratory animals, they also exhibit “sickness behavior.” In ancient times, when there were no antibiotic drugs, infectious disease took a huge toll. Thus, individuals who inherited the ability to produce cytokines in response to illness would be more likely to survive and produce offspring. It may be that clinical depression is in part a pathological variant of an evolved adaptation that is useful in combating infectious disease. All of these concepts, if confirmed, would also provide evidence depression is an evolved adaptation, in part at least. As Peter Richerson says, “Having the machinery for depression present may also lead to the machinery misfiring for various pathological reasons. Adaptations often come with costly tradeoffs. For the clinician, the distinction is important. If depression, say, upon the death of a spouse, is doing useful work, a clinician might do harm by treating the adaptation. On the other hand, if it is a case of misfiring due to excess sensitivity of the individual or novel stimulus in the modern environment the clinician would want to treat the symptoms that are doing no good.” As Darwin himself said in a letter, “Pain or suffering of any kind, if long continued, causes depression and lessens the power of action, yet it is well adapted to make a creature guard against any greater or sudden evil.”
Another clinical problem of ancient vintage is anxiety, or irrational fear. Anxiety can obviously be due to the person’s traumatic experiences, as in the post-traumatic stress so commonly observed in combat veterans, a proximal cause. In this case, a likely ultimate cause has been identified by Swedish psychologist Arne Ohman. He showed, by ingenious experiments, that people were much more easily conditioned to fear snakes and spiders than buttons or other neutral objects. It seems likely that this readiness to acquire certain kinds of fears is an evolved adaptation.
In conclusion, probably the main contribution that evolutionary psychology can make to clinicians is to encourage them to think about the “ultimate” causes of behavior and not only the “proximal” ones. This can only increase their effectiveness as researchers, assessors, and therapists. As Richerson says, “The task is to understand the evolved functions of psychological states so as to separate them from non-functional symptoms. The former one will probably not want to treat, whereas the latter one would.”
I very much appreciate the opportunity to share the beginning stages of my Darwin history project with readers of The Clinical Psychologist.
Acknowledgements: I wish to thank my wife, Margaret Gonzalez, for her excellent editorial suggestions on the first draft of this paper, and my 13-year-old grandson, Paul Martin, for letting me know that he found this same draft to be easy to read. Christopher Green, the well-known historian of psychology who teaches at York University in Toronto, made comments on the second draft that saved me from several inaccuracies and made this a more nuanced piece of writing. Evolution Peter Richerson gave the paper a very subtle reading. Nicola Foote of Florida Gulf Coast University, Lakshmi Gogate, and Michael Antoni of the University of Miami also made helpful comments.
Darwin and Clinical Psychology
Donald K. Routh
University of Miami