‘In the distant future I see open fields for more important researches. Psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by gradation.’

– Charles Darwin, 1859

Charles Darwin’s immense contribution to biology is as relevant and revolutionary in its implications now as when he first published On the Origin of Species just over 150 years ago.¹ Indeed his theory of the evolution of species by natural and sexual selection continues to have significance beyond the biological sciences, to philosophy, religion and the very essence of how we view our existence.

Furthermore, referring to it as a ‘theory’ is somewhat of a misnomer, in view of the extensive range of supporting evidence from disciplines as diverse as geology, genetics and biogeography.

Interestingly, however, significant numbers of people in the Western world, particularly in the US and, more recently, in the UK,² continue to believe in literal creationism or versions thereof, such as ‘intelligent design’. For example, a Gallup poll conducted in 2004 found that 45% of Americans polled agreed with the following, essentially creationist, statement: “God created humans pretty much in their present form at one time within the last 10,000 years or so.” 

A further 38% felt that life had evolved over millions of years from less advanced forms of life but that God had guided the process, so-called ‘theistic evolution’. Only 13% believed that humans developed from other life without guidance from God, ie. ‘materialistic evolution’, and the version espoused by Darwin himself.³ Thus Darwin’s ‘theory’ is still being debated, at a time when the level of undeniable supporting evidence has ensured that rejection of the theory of evolution by selection is by necessity linked to a faith-based belief in an alternative theory, or lack of belief in any existing explanation of life.   

A brief biography

Born in Shropshire, England, in 1809, Darwin came from a wealthy background and had a good scientific pedigree.⁴ Darwin’s father, Robert, and grandfather, Erasmus, were both doctors. Interestingly, Erasmus Darwin published a medical book called Zoonomia that included reference to early but underdeveloped ideas relating to the commonality of origin of all animals, with improvements transmissible from parents to offspring: it seems that evolutionary theory itself evolved through the Darwin family, reaching ultimate refinement in the mind of Charles. 

Following a brief stint at medical school in Edinburgh University, Darwin studied theology at Cambridge University but did not take holy orders. He was fascinated from an early age with all aspects of biology and wildlife, and it was this passion that drove him to take his famous round-the-world trip as naturalist on board the HMS Beagle from 1832 to 1836. The Galapagos Islands are perhaps the most noted of his stops on this voyage, but Darwin also visited many other parts of South America, and also touched on southern Africa, Australia, New Zealand and several other places in between. He sent home large amounts of specimens: rocks, fossils and plants and animals, both alive and dead. These dispatches home helped establish him as a famous naturalist even before his return, and this status was further strengthened by the publication of his memoirs of the voyage.⁵

Darwin was married to his first cousin, Emma Wedgwood, in 1840. The combined financial contributions to the couple of the Darwin and Wedgwood families was invested wisely and the annual return ensured that Darwin would be able to support his wife, 10 children (three of whom died in childhood) and a household staff without ever having to hold down a job or to earn a salary. Remarkably, Darwin never held an academic position.

Darwin first recorded his ideas on ‘transmutation’, a word used to signify the changeable nature of species, in 1844. However, he did not publish his ideas then but instead embarked on painstaking studies of molluscs and innumerable other subjects for many years in his home-based laboratory, publishing widely and making some novel discoveries, especially in the area of mollusc biology. We will never know if he would have got around to publishing his theory of evolution if it had not been for the work of a young naturalist called Alfred Russel Wallace,⁶ who forwarded his own (remarkably similar) ideas on the subject to Darwin in 1858. As a result, the two men had their findings jointly presented to the Linnaean Society in 1858,⁷ an event that initially passed by relatively quietly, but that was soon to rock the scientific establishment and society in general. 

Darwin’s notebooks prove that he had been developing his theories on ‘transmutation’ for the previous 20 years, based on his observations on the HMS Beagle and his own ‘home-work’ on molluscs and numerous other subjects. Potential reasons as to Darwin’s delay in publishing his findings include his own wish to produce as much supportive scientific evidence as possible, an ambivalence about publishing a Godless theory in a religious society and, at a personal level, a reluctance to offend his devoted wife Emma, who was a devout Christian.³

The appearance of the first edition of On the Origin of Species in 1859 established Darwin as one of the leading scientists of his generation, and he continued to publish widely right up until the year of his death on subjects within natural science as diverse as orchids, insectivorous plants, vegetable mould and, of most relevance to this paper, the expression of emotions in man and animals.⁸

Darwin’s (direct) contribution to modern psychology and psychiatry

Charles Darwin contributed directly to modern psychology and psychiatry in the form of his book, The Expression of the Emotions in Man and Animals, which was effectively the first textbook on human evolutionary psychology and psychiatry.⁸ His indirect contribution (see next section) is far more significant, however, and involves the application of evolutionary principles to psychology and psychiatry by many other scientists over the past century and a half and up to the present day. 

In his book on the subject, Darwin described the expression of various emotions in man and in some animals and derived three primary principles, as described in the first three chapters: firstly, “that serviceable actions become habitual in association with certain states of the mind, and are performed whether or not of service in each particular case”; secondly, “the principle of antithesis”; and, thirdly, “the principle of the direct action of the excited nervous system on the body, independently of the will and in part of habit.” As the focus of his book was primarily on the expression of ‘normal’ emotions, as opposed to the psychopathology seen in psychiatric disorders, this book relates mainly to what we now term ‘evolutionary psychology’, as opposed to ‘evolutionary psychiatry’.

Chapters 4 and 5 focused on means of expression in animals and chapters 6-13 focused on the expression of emotions in man. The fascinating chapter titles include: “Joy, High Spirits, Love, Tender Feelings, Devotion” (Chapter 8); “Hatred and Anger” (Chapter 10); and “Surprise, Astonishment, Fear, Horror” (Chapter 12). Detailed descriptions of the outward expressions of emotions are provided, as in the sections on ‘elevation of the eyebrows’ in the chapter on “Surprise, Astonishment, Fear, Horror” and in the section on the nature of blushing in the chapter on “Self-attention, Shame, Shyness, Modesty” (Chapter 13).

In the concluding chapter, Darwin states: “We have seen that the study of the theory of expression confirms to a certain limited extent the conclusion that man is derived from some lower animal form, and supports the belief of the specific or subspecific unity of the several races; but as far as my judgement serves, such confirmation was hardly needed.”

Darwin’s (indirect) contribution to modern psychology and psychiatry

Despite the universal acceptance of evolutionary theory in all branches of the biological sciences, evolution is effectively ignored in conventional ‘Western’ medicine and in psychiatry and psychology, the focus of this article.

As highlighted in the previous section, the concept of an evolutionary approach to psychiatry and psychology has been around from Darwin’s time. However, evolutionary approaches to the study of human nature have had short-lived success in the one and a half centuries since On the Origin of Species, partly due to difficulties with providing empirical evidence or ‘proof’ and partly due to the corruption and perversion of such ideas in the abuses of Social Darwinism and eugenics in Nazi Germany. 

Perhaps most importantly, there is only yet an emerging evidence base (see below) on the practical, clinical applications of evolutionary theory to psychology and psychiatry, and this area remains a challenge to researchers and clinicians with an interest in the subject.

Despite these problems and shortcomings, an undeniable fact remains that evolution is one of the central platforms of biology and, if psychology and psychiatry are to be considered as belonging to the biological (as opposed to the social) sciences, then evolutionary theory must have relevance to the study of the human mind.

The year 2000 saw the publication of a textbook on the topic of evolutionary psychiatry⁹ and a controversial editorial by RT Abed in the British Journal of Psychiatry¹⁰ that led to a flurry of correspondence to that journal.

The central points of Abed’s editorial were to define the differences between theories of ultimate and proximate causation for biological phenomena, to emphasise the importance of integrating psychology and psychiatry firmly into biology and the highlighting of the many contributions of evolutionary theory to psychology and psychiatry.

Ultimate causation involves an understanding of the contributions of a trait or system to the reproductive fitness of an organism in its natural (ancestral) environment, while proximate causes are the sum of all the biological processes (biochemical, physiological, etc.) that directly produce a given phenomenon. Abed went on to explain how ultimate causation answers the question why a trait or system exists, whereas proximate causation explains how it works. In relation to depression, for example, proximate explanations focus on the genetic, biochemical and neurophysiological phenomena observed. In contrast, ultimate causation focuses on why such a common state exists and asks if there are reproductive advantages to ‘normal’ depressed mood or even to clinical depression.

An evolutionary line of thinking in relation to depressed mood might follow thus. ‘Normal’ depressed mood is universal, and clinical depression is also very common, with a lifetime prevalence of 10-20%. Furthermore, ‘normal’ transitory depressed mood and clinical depression are characterised by certain core features seen across different cultures and these conditions may therefore serve an adaptive function for the individual. This adaptive function may work in a number of ways, eg. it may help the individual to avoid physical conflict or to elicit help in times of need, it may help the individual to become more introverted and develop a helpful ‘depressive realism’ in their thinking, and it may help the individual to adjust to a loss. Darwin himself more than hinted at an evolutionary approach to depression when he stated: “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 itself against any great or sudden evil.”¹¹ The issue of whether clinical depression, as opposed to ‘normal’ transitory depressed mood or sadness, is adaptive, remains controversial.¹²

The evolutionary mechanism involved in the above discussion on depression could be referred to as a ‘gradualist’ view, with the assumption that significant selection for characteristics in the population is occurring all the time, and is potentially differential between populations. 

TJ Crow, in contrast, describes a ‘saltational’ or sudden change in relation to the evolutionary aetiology of schizophrenia.¹³ Crow describes the hypothesis whereby speciation events occur selectively on the heterogametic chromosome (the Y chromosome in mammals) and are followed by a phase of sexual selection to establish a new specific mate recognition system. In humans, it is argued that the core component of this system is the capacity for language and that the nuclear symptoms of schizophrenia are necessary clues to its neural structure. 

A recent paper by an Irish group has again raised the issue of an evolutionary perspective applied to psychotic symptoms in the general population.¹⁴

Abed pointed out further examples of contributions of evolutionary theory to psychology and psychiatry, eg. the different nature of sexual jealousy in men and women, with men being more preoccupied with issues relating to paternity certainty and women being more preoccupied with the provision of resources for their offspring;¹⁵ modularity of the mind;¹⁶ human violence, including child abuse and homicide;¹⁷ depression;¹² anxiety and related disorders;¹⁸ eating disorders;¹⁹ obsessive-compulsive disorder;²⁰ and anti-social personality disorder.²¹

Critics of evolutionary theory in psychology and psychiatry question its theoretical basis and clinical relevance and warn against the perversion of such theories for political reasons.²²

Conclusions

Charles Darwin may have been reluctant to offend his wife and wider Victorian society by publishing his theory of natural selection in 1859. Little did he know that, 150 years later, his ideas would continue to generate heated debate in science and religion. Despite undeniable evidence supporting the centrality within biology of Darwin’s ‘theory’ of evolution by natural and sexual selection, it has always proved to be controversial and open to misinterpretation. Modern psychiatry and psychology take relatively little notice of the evolutionary perspective, despite emerging evidence for the applications of evolutionary theory in both disciplines. At a time when ‘biological psychiatry’ has taken on a sometimes limited meaning, often overly focused on questionable and over-simplistic neurotransmitter theories, psychiatry and psychology are in need of the fresh perspectives that evolutionary theory would bring to the study of the human mind. 

Declaration of interest: none.

References

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