Human Paleopsychology

Human Paleopsychology

Mismatch Theory

         At the Human Behavior and Evolution Society meeting in Santa Barbara in 1995, I had the opportunity to introduce mismatch theory on a panel assembled by Charles Crawford of Simon Fraser University in Burnaby, British Columbia.  Along with Professor Crawford and myself, S. Boyd Eaton and Randy Nesse presented papers.  My presentation led to a four article series on mismatch theory published in the ASCAP Newsletter in 1996.  
       My presentation at the 1995 convention in Santa Barbara was the first time, I believe, that the concept of evolutionary mismatch was used in an academic setting.    However, popular evolutionary writer, Robert Wright, had first used the concept months earlier in a fascinating article in Time Magazine on depression- “The Evolution of Despair.”  Since that time, mismatch theory has become a central organizing construct in various evolutionary approaches in psychology, sociology, psychiatry, and medicine.
      In my 1995 presentation, the five fundamental assumptions of Mismatch Theory were set forth:
1.  human morphology and behavior originally evolved in zones of time called EEAs (environments of evolutionary                  adaptation). These ancient zones of change were in effect from the first pre-human beings, and as they continued             to evolve, step by step, into modern humans.
2. the human species ceased to evolve, to any great degree, beyond late Homo sapiens 40,000 years ago.
3.  massive cultural and environmental change has occurred in the past 40,000 years.  This change has been enormous in      the recent agricultural, industrial, and informational, and cybernetic revolutions.
4. modern human beings often find their naturally evolved selves (their fundamental human natures) mismatched or at
    odds with the current physical, social, and cultural environments.
5. the frequency and magnitude of mismatch for a given individual is positively correlated with levels of both physical         and psychological pathology.
     Modern human beings occasionally experience circumstances that are similar to those of our ancestors in phylogeny- such as taking a walk in the woods, going on a camping trip, or roasting a pig and sharing it with close friends.  However, highly encultured humans in first-world countries are far more likely to experience situations highly dissimilar to ancestral ones in the course of their daily lives.  This antagonism between the ancient inner self and modernity can lead to anxiety, discomfort, and confusion.  In the extreme, such human nature/modern culture mismatch can lead to physical illness and/or psychopathology.
     Monitor your behavior for a day, and then estimate how many of your outputs were evolutionarily "adaptive"- that is, were reasonably well-matched with ancestral experience both environmentally and psychologically.  You will quickly see that you are anything but a robot running off evolved programs irrespective of current context or current frame of mind.
    Indeed, we ultra-moderns are not “gene machines” constantly acting out evolved adaptive programs as Dawkins (1976 ) suggests, but we are, rather, occasional adapters whose outputs are often non-adaptive or even maladaptive.  However, the healthy person manages enough “matches” to satisfy the requirements of human nature.
     In modern America, we can choose to ignore many of Mother Nature’s demands to “match” with her, and still live decent and even noteworthy lives.  Indeed, most “successful” Americans appear much more inclined toward “matching” with their culture than with their biology.
    Human beings are highly adaptable and can survive and prosper in many disparate environments.  For example, a person who is highly mismatched biologically (e.  g., an overweight, type-A smoker who works 15 hours a day in a loud, contentious newsroom) might still be reasonably healthy and happy due to a few, high quality "matches" (has a loving and supportive mate, goes fishing every weekend, and sleeps a good eight hours every night).  Indeed, one of the great challenges of mismatch theory is to specify the quantity and quality of "matches" that are necessary for the good life.
     In sum, it is not a question of whether we moderns are mismatched or not, but one of how we can avoid pathological mismatches, on the one hand, and manage a sufficient number of “matches” with nature on the other to be psychologically healthy and happy.
The Widening Nature-Culture Mismatch
"...we are specifically adapted to Stone Age conditions.  These conditions ended a few thousand years ago, but evolution has not had time since then to adapt us to a world of dense populations, modern socioeconomic conditions, low levels of physical activity, and the many other novel aspects of modern environments.  We are not referring merely to the world of offices, classrooms, and fast-food restaurants.  Life on any primitive farm or in any third-world village may also be thoroughly abnormal for people whose bodies were designed for the world of the Stone Age hunter-gatherer "(Nesse & Williams, 1994, p. 134).
     Human beings have become progressively more mismatched over the past 40,000 years, but the rate of mismatch has grown at a geometric pace in recent times.  Persons living in modern technological cultures experience the greatest degree of nature-culture mismatch in the history of the human race, and future generations may expect even more drift away from the archaic hunting and gathering self.
     From the first human to the present, around 99% of our ancestors were hunter-gatherers and that way of life defines our human nature.  During those eons of time in the hunting and gathering era, biological and cultural evolution were fairly closely matched.  Culture was presumably little more than the natural extension of survival and reproductive functions and the tribal and social imperatives devoted to hunting and gathering.
     In the earliest phases, there was minimal emphasis on transgenerational storage of cultural information, and little formalization and symbolization of rituals, concepts, and ideologies for their own sake. Behavior and thinking were little more than natural emanations of the hunting and gathering way of life.
     As evolution progressed over time, cultural change proceeded at a vastly faster rate than biological change and culture began to take on a life of its own.  Humans were now more than just hunters and gatherers; they were becoming cultural beings with the capability to separate, to a degree, their way of life from their biology.
     Culture began to rule over hunting, gathering, food processing and storage, shelter construction, and weapons development and refinement.  Such technological innovations were probably instituted by a small minority of the brightest, most curious, and luckiest members of the band or tribe, but everyone profited from their efforts.  The price paid for these valuable innovations was an increasing separation of human nature from the its most ingenious invention- culture.
Definitions and Distinctions
The term  match refers to an emotional/behavioral/cognitive state or situation that closely approximates a similar one in archaic human history.  For example, a hike through the woods “matches” but is not identical to ancestral hunting treks or migratory behavior.  It is rare for modern humans to emit outputs nigh-identical to original ones.

The term rematch refers to the release of ancient outputs more-or-less in their entirety.  The process of phylogenetic regression, in its stronger forms, is a form of rematching where ancient mechanisms are re-activated and expressed with minimal modification through the cognitive or moral systems.  When we are overcome with rage or in the throes of sexual orgasm, we respond in a manner very close to that of our early ancestors.    

A mismatch, as we have seen, occurs when the basic human nature: culture interaction differs appreciably from analogous ones in ancestral time.   The possibilities for mismatch are seemingly endless, for mismatch can be effected by exposure to any environment or context that appreciably differs from the original hunting and gathering contexts of our forebears. 
Mismatch and Cancer
     The mismatch line of reasoning has been productively applied to the genesis and treatment of physical disease including cancers of various types, obesity and diabetes, osteoporosis, heart disease, and dietary under- and over-sufficiencies, allergies and autoimmune diseases, myopia, drug addiction and even impacted wisdom teeth and fallen arches!
     In the psychological and social domains, mismatch theory has helped us better understand modern angst, depression and despair, the “war” of the sexes, problems in the classroom and the workplace, racial animus, group hostility and warfare, and the problems of modern life in general.  It has also become a powerful tool of understanding for the psychotherapist and psychiatrist as well (Bailey, 2000).  Clearly, mismatch theory is of major relevance to physical and psychological health and human behavior in general.

      Cancer is perhaps nature’s most mystifying and dreadful disease.  It is the bête noire of the  Caveman Syndrome: those killer diseases that stem from mismatch between our ancient hunting and gathering selves and our modern selves.  The role of mismatch in the genesis, development, and treatment of cancer has been a major focus in the relatively new field of  evolutionary medicine.
     Athena Aktipis  and Randolph Nesse address the mismatch-cancer link in detail their path-breaking article, “Evolutionary Foundations for Cancer Biology.”  They tell us that natural selection moves “too slow to adapt bodies to rapidly changing environments (p. 3)” and this produces mismatched conditions.  They point out that population migration from colder, less sunny environments to warmer, more sunny ones is an important mismatch, as are rising rates of obesity, higher rates of fat intake, use of tobacco, and even exposure to artificial light at night carries risk factors.  They conclude: “When considering all cancers, the role of mismatch with modern environments is overwhelming (p. 11).”
     In mismatch, there is a separation, a kind of psychological “migration” where the current context pulls the individual away from his or her natural moorings in the hunting and gathering way of life.  I believe that stress, broadly defined, is a result of this kind of mismatched condition.  Therefore, as an instigator of stress, mismatch may directly cause some pathological conditions, aggravate and exacerbate others, and, thus, is a major moderator of pathological conditions, both physical and psychological.

     This is especially true regarding the most fearsome disease- cancer.  The National Cancer Institute takes a conservative approach and concludes that the evidence for stress causing cancer directly is not strong.  But the role of stress in aggravating and otherwise mediating the onset, duration, mechanisms of DNA repair, and metastasis of cancer is substantial.
Stress-induced impairment of the immune system is a major factor in the stress-cancer connection.  This may occur by weakening of anti-tumor defense or by encouraging new tumor-feeding blood vessels to form.  Chronic stresses associated associated with depression and social isolation are especially important in cancer growth and progression.


Stress, Mismatch, and the Age of Depression

     Mismatch theory applies with considerable force in the physical domain of cancer and it, likewise, applies to the psychological domain of depression as well.  As we learned on the phylogenetic regression page herein, ancestral humans- such as hunters and gatherers- lived in “zones of normality” where they went about the business of survival and reproduction under everyday conditions of numerous mild stresses and interruptions. 
     Occasionally, however, the threat of physical injury or death- or actual injury- would set off the flight-or-fight system and put the individual in a “regressive,” survival mode of functioning.  The sympathetic autonomic nervous system would exert powerful dominance over the parasympathetic system, energy levels would be vastly increased, blood would rush from internal organs to the muscles, and fight or flight behavior would follow.

     Concurrently, he or she would experience the emotion of overwhelming apprehension and fear, and the whole process would involve great energy depletion, wear and tear on the body, and emotional exhaustion.

     Thus, we see that severe stress in ancient humans reflected a trade-off between injury or death, on the one hand, and considerable physical and emotional costs on the other.  Fortunately for them, each stressful episode came and went like a summer storm, and “long-term” or “chronic” stress was likely not the issue it is in modern humans.

     I doubt that the ancients obsessively “ruminated” all that much about possible future adversities as do we moderns; their focus was predominately on the threat at hand.  One of the great mismatch features of today’s world is for people to imagine a thousand adversities for each one actually encountered!

     Ancestral humans immediately escaped or fought adversity- and paid a relatively small price physically and psychologically.  Today, we literally wallow in imagined dangers, and we pay a great price in terms of both physical and psychological health.  In sum, most of our “stress” is chronic,  internal, self-imposed and cognitively magnified.

     All of this leads to a multitude of psychological mismatch pathologies including panic, anxiety, obsessiveness, and depressive reactions, and things continue to get worse rather than better.   All of these “over” reactions keep us in a chronic state of stress and distress, and the drug companies are reaping the benefits.

      There was talk of the “Age of Anxiety” a few years back, but, I believe we are becoming more the “Age of Depression” every day.  Indeed, many of today’s behavioral scientists speak of a “world-wide epidemic of depression.”  Whereas, anxiety is a chronic and fearful obsession about future adversity, depression reflects a kind of resignation and pessimism about resolving real or imagined adversity and, indeed, it often questions the worth of life itself.  “Shall I give up or shall I fight” is its mantra.

Some evolutionary explanations of depression:

  • A functional ruminative state focusing on overcoming social obstacles
  • A period of lowered activity, low positive affect, and increased vigilance
  • A signal to self and others of “giving up”
  • A functional submission/appeasement display
  • A social signal of helplessness to encourage social support from others
  • A “giving up” in reaction to severe loss or sense of abject failure
  • A kind of “fish out of water” mismatch reaction
  • A kind of “restful period” for regaining strength and resolve
  • A “failure to nurse” in post-partum depression
  • A subconsciously or semi-consciously perceived sense of failure in meeting species imperatives of survival, mating, and rearing offspring

     Each of the above ideas represent a piece of the depression picture. Note that a number of them revolve around the presumed adaptive functions of the depressive response.  A strict mismatch approach stresses the maladaptive aspects of distancing ourselves from nature in the causation of pathology, but it also recognizes the importance of employing older adaptations in problem mitigation and solution.

     My paleopsychological approach focuses on the last explanation listed above-- failure in meeting species goals of survival, reproduction, and successful rearing of offspring.  I believe that much of the world’s depression would disappear if these four conditions were met:

1.  The individual is able to “survive” until mating age in an intact,  reasonably well-functioning family and “tribal” setting.

2. The individual is able to secure a faithful and loving mate.

3. The individual and his/her mate produce healthy and loving offspring who are able well-integrate themselves into both their families and society at large.

4. The offspring continue this “healthy” pattern and life style in succeeding generations.

    As a psychotherapist, trainer of several generations of psychotherapists, and originator of the kinship model of psychotherapy (see Bailey, 2000), meeting these four fundamental “species conditions” goes to the very heart of human health and happiness.

    I once commented to a student that if “I could somehow provide an adoring mate for the lonely masses of adults out there, then much of what we call mental illness would disappear!”  And having a mate is just one of the species conditions for the good life.

     Hunter-gatherers met the four “ideal family” conditions fairly well within their simpler contexts, but modern humans are failing miserably in the family context.”  We see why anxiety, depression and a fractured sense of self are the whelming social diseases of our age.   

Concluding Comment

     It is clear that modern human beings are grievously mismatched relative to their ancestors in phylogeny such as the prototypical hunters and gatherers who accounted for 99% of our history as a species.  Moreover, this mismatch appears to play a causal role in many forms of physical and psychological pathology, and is probably a significant aggravating factor in most human ills. 

     Indeed, failure to sufficiently match with our ancestral past leads to internal discontent and despair, and a vague sense of incompleteness and anxiety.  Then, after a few real or imagined interruptions or failures, this internal discontent readily and easily morphs into despair and depression. 

The role of cities in causing/aggravating depression

     As Logan and Jacka (2014) tell us, “In 21st-century public health rapid urbanization and mental health disorders are a growing global concern.”  They argue that urban expansion, climate change, cultural and technological changes, and global industrialization and ultraprocessing of food are among the pressing mismatch issues of our age. 

     They also tell us that the size, density, and heterogeneity of cities will continue in both developed and developing nations.  By the year 2050, 86% of those in the “developed” category and 64% of those in the “developing” category will be urban residents.  

     Given that city life breeds ancestral self/current self “mismatch” by definition, then as we continue to concentrate ourselves into ever larger cities the diseases of civilization will increase accordingly.

     Moreover, Logan and Jacka see major depression and anxiety as major players in the “impending global epidemic.”  They conclude that global urbanization and an impending mental health crisis are a “tandem juggernaut moving at a rapid speed.” 
The role of gender in causing/aggravating depression

     Most experts agree that the human female is, in general, more adaptable than the male.  She certainly tends to live a lot longer than the male, but she appears much more susceptible to diseases of civilization like anxiety and depression.  In many important ways, the modern female is more mismatched than her male counterparts. 

     We learned on the phylogenetic regression page herein that the female is a “dedicated reproductive unit, and, once pregnant she was/is a virtual prisoner of her hormones, bodily changes and the thrust of new life.”  This has been the story for the female throughout ancestral and pre-industrial history, but how that has changed in recent times!

     In modern society, males can still hunt, provide and protect as in the past, and they can luxuriate in male competitiveness in the military, on the athletic field, or watching their favorite athletes on TV.  Moreover, they have some raging hormones, but nothing to compare with that of the distaff side.

     This suggests to me that the modern female is fighting- whether aware or not- far more momentous mismatch battles than the modern male.  Ancestrally, (1) her dependence on and fondness for intense social relations in the band and tribe environment- especially between mother/infant, and female-to-female interactions; (2) her dependence on males for provision and protection; (3) her highly circumscribed work role in the division of labor; and (4) her geographically circumscribed life at the home base, tend to clash greatly with current women’s liberated and expanded social roles.

     We should not be surprised that today’s woman- who prospers on the college campus and embraces modernity and the wonders of advanced civilization with a vengeance- must necessarily pay a large “mismatch price” in terms of anxiety, depression, and other pathologies.

     Whereas males must give up much of his ancestral self to succeed culturally in first-world countries, the female must suppress, deny, and otherwise hide most of her ancient life-giving nurturing, and group-supporting qualities.

     All of this plays out dramatically in one of the defining diseases of modern civilization- postpartum depression (Holbrook and Haselton, 2014).  Approximately 13% of women worldwide will experience depressive symptoms within the first three months postpartum, leading to harmful disruptions in parenting behavior, marriage relations, and may even be a factor in early infant death. 

     These authors raise the interesting possibility that depressive symptoms may represent a functional suite of sickness-like behaviors employed to decrease activity, on the one hand, and increase vigilance, on the other, when activation of the immune system signals internal or external stress.

     They also discuss some of the mismatch stressors encountered by new mothers in the areas of poor diet, early weaning, low activity levels, insufficient sunlight, isolation from kin, and the effects of inflammation in the body’s system. 

     The fields of obstetrics and pediatrics have made monumental strides in neonatal and maternal health in the past century, and mismatch theory stands poised to identify and encourage additional ones.  Looking back upon the wisdom of our ancestors and their ways of bringing new life into the world is a good place to start. 


Aktipis, C. A. & Nesse, R. M.  (2013).  Evolutionary foundations for cancer biology.  Evolutionary Applications, 6(1), 144-159.

Bailey, K. G. (1995).  Mismatch theory and psychopathology.  Paper presented at the Human Behavior and Evolution Society meeting in Santa Barbara, CA.     
Bailey, K. G. (2000).  Evolution, kinship, and psychotherapy: Promoting psychological health through human relationships.  In Gilbert, P. & Bailey, K. G. (eds.), Genes on the Couch: Explorations in Evolutionary Psychotherapy. Taylor and Francis: Philadelphia, PA.

Hahn-Holbrook, J. & Haselton, M. (2014).  Is postpartum depression a disease of modern civilization?  Current Directions in Psychological Science, Vol. 23(6), 395-400.

Logan, A. C. & Jacka, F. N. (2014).  Nutritional psychiatry research: an emerging discipline and its intersection with global urbanization, environmental challenges, and evolutionary mismatch.  Journal of Physiological Anthropology, 33(22), 1-16.

Nesse, R. M. & Williams, G. C. (1994).  Why We Get Sick:  The new science of  Darwinian medicine.  New York: Random House.   


Robert Wright
Selfish Gene
Caveman Syndrome
Evolutionry Medicine 1996
Mismatch and Cancer

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Kent G. Bailey [email protected]