More recently, the merge between the biological science and
applied sciences gave birth to new fields that are extensions of
evolutionary biology, including evolutionary robotics, engineering, algorithms, economics, and architecture.
The basic mechanisms of evolution are applied directly or indirectly to
come up with novel designs or solve problems that are difficult to
solve otherwise. The research generated in these applied fields in turn,
contribute to progress, especially thanks to work on evolution in computer science and engineering fields such as mechanical engineering.
In evolutionary developmental biology the different processes of
development can play a role in how a specific organism reaches its
current body plan. The genetic regulation of ontogeny and phylogenetic
process is what allows for this kind of understanding of biology to be
possible. Looking at different processes during development, and going
through the evolutionary tree, one can determine at which point a
specific structure came about. For example, the three germ layers can be
observed to not be present in cnidarians and ctenophores, which instead
present in worms, being more or less developed depending on the kind of
worm itself. Other structures like the development of Hox genes and
sensory organs such as eyes can also be traced with this practice.
The idea of evolution by natural selection was proposed by Charles Darwin in 1859, but evolutionary biology, as an academic discipline in its own right, emerged during the period of the modern synthesis in the 1930s and 1940s. It was not until the 1980s that many universities had departments of evolutionary biology. In the United States, many universities have created departments of molecular and cell biology or ecology and evolutionary biology, in place of the older departments of botany and zoology. Palaeontology is often grouped with earth science.
Microbiology too is becoming an evolutionary discipline, now that microbial physiology and genomics are better understood. The quick generation time of bacteria and viruses such as bacteriophages makes it possible to explore evolutionary questions.
Current research in evolutionary biology covers diverse topics and incorporates ideas from diverse areas, such as molecular genetics and computer science.
Second, biologists ask the most straightforward evolutionary question: "what happened and when?". This includes fields such as paleobiology, as well as systematics and phylogenetics.
Third, the modern evolutionary synthesis was devised at a time
when nobody understood the molecular basis of genes. Today, evolutionary
biologists try to determine the genetic architecture of interesting evolutionary phenomena such as adaptation
and speciation. They seek answers to questions such as how many genes
are involved, how large are the effects of each gene, how interdependent
are the effects of different genes, what do the genes do, and what
changes happen to them (e.g., point mutations vs. gene duplication or even genome duplication). They try to reconcile the high heritability seen in twin studies with the difficulty in finding which genes are responsible for this heritability using genome-wide association studies.
One challenge in studying genetic architecture is that the classical population genetics that catalysed the modern evolutionary synthesis
must be updated to take into account modern molecular knowledge. This
requires a great deal of mathematical development to relate DNA sequence
data to evolutionary theory as part of a theory of molecular evolution. For example, biologists try to infer which genes have been under strong selection by detecting selective sweeps.
Fourth, the modern evolutionary synthesis involved agreement
about which forces contribute to evolution, but not about their relative
importance. Current research seeks to determine this. Evolutionary forces include natural selection, sexual selection, genetic drift, genetic draft, developmental constraints, mutation bias and biogeography.
An evolutionary approach is key to much current research in organismal biology and ecology, such as in life history theory. Annotation of genes and their function relies heavily on comparative approaches. The field of evolutionary developmental biology ("evo-devo") investigates how developmental processes work, and compares them in different organisms to determine how they evolved.
Many physicians do not have enough background in evolutionary biology, making it difficult to use it in modern medicine.
Drug resistance today
Evolution
plays a role in resistance of drugs. For example, how HIV becomes
resistant to medications and the body's immune system. The mutation of
resistance of HIV is due to the natural selection of the survivors and
their offspring. The one HIV that survived the immune system reproduced
and had offspring that were also resistant to the immune system.
Drug resistance also causes many problems for patients such as a
worsening sickness or the sickness can mutate into something that can no
longer be cured with medication. Without the proper medicine a sickness
can be the death of a patient. If their body has resistance to a
certain number of drugs, then the right medicine will be harder and
harder to find. Not finishing an antibiotic is also an example of
resistance that will cause the bacteria or virus to evolve and continue
to spread in the body.
When the full dosage of the medication does not enter the body and
perform its proper job, the virus and bacteria that survive the initial
dosage will continue to reproduce. This makes for another sickness later
on that will be even harder to cure because this disease will be
resistant to the first medication used. Finishing medicine that is
prescribed is a vital step in avoiding antibiotic resistance. Also,
those with chronic illnesses, illnesses that last throughout the
lifetime, are at a greater risk to antibiotic resistance than others.
This is because overuse of a drug or too high of a dosage can cause a
patient's immune system to weaken and the illness will evolve and grow
stronger. For example, cancer patients will need a stronger and stronger
dosage of medication because of their low functioning immune system.
Evolutionary mismatch, also known as mismatch theory or evolutionary trap, is a concept in evolutionary biology that refers to evolved traits that were once advantageous but became maladaptive
due to changes in the environment. This can take place in humans and
animals and is often attributed to rapid environmental change.
Timeline showing a period of mismatch following an environmental change.
Mismatch theory represents the idea that traits that evolved in an organism in one environment
can be disadvantageous in a different environment. This environmental
change leading to evolutionary mismatch can be broken down into two
major categories: temporal (change of the existing environment over
time, e.g. a climate change) or spatial (placing organisms into a new
environment, e.g. a population migrating).
Since environmental change occurs naturally and constantly, there will
certainly be examples of evolutionary mismatch over time. However,
because large-scale natural environmental change – like a natural
disaster – is often rare, it is less often observed. Another more
prevalent kind of environmental change is anthropogenic (human-caused).
In recent times, humans have had a large, rapid, and trackable impact on our environment, thus creating scenarios where it is easier to observe evolutionary mismatch.
Because of the mechanism of evolution
by natural selection, the environment ("nature") determines ("selects")
which traits will persist in a population. Therefore, there will be a
gradual weeding out of disadvantageous traits over several generations
as the population becomes more adapted to its environment. Any
significant change in a population's traits that cannot be attributed to
other factors (such as genetic drift
and mutation) will be responsive to a change in that population's
environment; in other words, natural selection is inherently reactive.
Shortly following an environmental change, traits that evolved in the
previous environment, whether they were advantageous or neutral, are
persistent for several generations in the new environment. Because evolution is gradual
and environmental changes often occur very quickly on a geological
scale, there is always a period of "catching-up" as the population
evolves to become adapted to the environment. It is this temporary
period of "disequilibrium" that is referred to as mismatch.
Mismatched traits are ultimately addressed in one of several possible
ways: the organism may evolve such that the maladaptive trait is no
longer expressed, the organism may decline and/or become extinct as a
result of the disadvantageous trait, or the environment may change such
that the trait is no longer selected against.
History
As evolutionary thought became more prevalent, scientists studied and attempted to explain the existence of disadvantageous traits, known as maladaptations, that are the basis of evolutionary mismatch.
The theory of evolutionary mismatch began under the term evolutionary trap as early as the 1940s. In his 1942 book, evolutionary biologist Ernst Mayr
described evolutionary traps as the phenomenon that occurs when a
genetically uniform population suited for a single set of environmental
conditions is susceptible to extinction from sudden environment changes. Since then, key scientists such as Warren J. Gross and Edward O. Wilson have studied and identified numerous examples of evolutionary traps.
The first occurrence of the term "evolutionary mismatch" may have been in a paper by Jack E. Riggs published in the Journal of Clinical Epidemiology in 1993.
In the years to follow, the term evolutionary mismatch has become
widely used to describe biological maladaptations in a wide range of
disciplines. A coalition of modern scientists and community organizers
assembled to found the Evolution Institute in 2008, and in 2011
published a more recent culmination of information on evolutionary
mismatch theory in an article by Elisabeth Lloyd, David Sloan Wilson, and Elliott Sober. In 2018 a popular science book appeared by evolutionary psychologists on evolutionary mismatch and the implications for humans.
Many members of the scientific community continue to explore the effects of evolutionary mismatch in our quickly changing world.
Mismatch in human evolution
The Neolithic Revolution: transitional context
The Neolithic Revolution brought about significant evolutionary changes in humans; namely the transition from a hunter-gatherer lifestyle, in which humans foraged for food, to an agricultural lifestyle. This change occurred approximately 10,000–12,000 years ago.
Humans began to domesticate both plants and animals, allowing for the
maintenance of constant food resources. This transition quickly and
dramatically changed the way that humans interact with the environment,
with societies taking up practices of farming and animal husbandry.
However, human bodies had evolved to be adapted to their previous
foraging lifestyle. The slow pace of evolution in comparison with the
very fast pace of human advancement allowed for the persistence of these
adaptations in an environment where they are no longer necessary. In
human societies that now function in a vastly different way from the
hunter-gatherer lifestyle, these outdated adaptations now lead to the
presence of maladaptive, or mismatched, traits.
Some modern human populations engage in hunter-gatherer practices.
Human disease
Obesity and diabetes
Human bodies are predisposed to maintain homeostasis,
especially when storing energy as fat. This trait serves as the main
basis for the "thrifty gene hypothesis", the idea that "feast-or-famine
conditions during human evolutionary development naturally selected for
people whose bodies were efficient in their use of food calories".
Hunter-gatherers, who used to live under environmental stress, benefit
from this trait; there was an uncertainty of when the next meal would
be, and they would spend most of their time performing high levels of
physical activity. Therefore, those that consumed many calories would
store the extra energy as fat, which they could draw upon in times of
hunger.
However, modern humans have evolved to a world of more sedentary
lifestyles and convenience foods. People are sitting more throughout
their days, whether it be in their cars during rush hour or in their
cubicles during their full-time jobs. Less physical activity in general
means fewer calories burned throughout the day. Human diets have changed
considerably over the 10,000 years since the advent of agriculture,
with more processed foods in their diets that lack nutritional value and
lead them to consume more sodium, sugar, and fat. These high calorie,
nutrient-deficient foods cause people to consume more calories than they
burn. Fast food combined with decreased physical activity means that
the "thrifty gene" that once benefit human predecessors now works
against them, causing their bodies to store more fat and leading to
higher levels of obesity in the population.
Obesity is one consequence of mismatched genes. Known as "metabolic syndrome", this condition is also associated with other health concerns, including insulin resistance, where the body no longer responds to insulin secretion, so blood glucose levels are unable to be lowered, which can lead to type 2 diabetes.
Osteoporosis
Another human disorder that can be explained by mismatch theory is the rise in osteoporosis
in modern humans. In advanced societies, many people, especially women,
are remarkably susceptible to osteoporosis during aging. Fossil
evidence has suggested that this was not always the case, with bones
from elderly hunter-gatherer women often showing no evidence of
osteoporosis. Evolutionary biologists have posited that the increase in
osteoporosis in modern Western populations is likely due to our
considerably sedentary lifestyles. Women in hunter-gatherer societies
were physically active both from a young age and well into their
late-adult lives. This constant physical activity likely lead to peak
bone mass being considerably higher in hunter-gatherer humans than in
modern-day humans. While the pattern of bone mass degradation during
aging is purportedly the same for both hunter-gatherers and modern
humans, the higher peak bone mass associated with more physical activity
may have led hunter-gatherers to be able to develop a propensity to
avoid osteoporosis during aging.
Hygiene hypothesis
The hygiene hypothesis,
a concept initially theorized by immunologists and epidemiologists, has
been proved to have a strong connection with evolutionary mismatch
through recent year studies. Hygiene hypothesis states that the profound
increase in allergies, autoimmune diseases, and some other chronic
inflammatory diseases is related to the reduced exposure of the immune
system to antigens. Such reduced exposure is more common in
industrialized countries and especially urban areas, where the
inflammatory chronic diseases are also more frequently seen.
Recent analysis and studies have tied the hygiene hypothesis and
evolutionary mismatch together. Some researchers suggest that the overly
sterilized urban environment changes or depletes the microbiota
composition and diversity. Such environmental conditions favor the
development of the inflammatory chronic diseases because human bodies
have been selected to adapt to a pathogen-rich environment in the
history of evolution.
For example, studies have shown that change in our symbiont community
can lead to the disorder of immune homeostasis, which can be used to
explain why antibiotic use in early childhood can result in higher
asthma risk.
Because the change or depletion of the microbiome is often associated
with hygiene hypothesis, the hypothesis is sometimes also called "biome
depletion theory".
Human behavior
Behavioral examples of evolutionary mismatch theory include the abuse of dopaminergic pathways and the reward system. An action or behavior that stimulates the release of dopamine,
a neurotransmitter known for generating a sense of pleasure, will
likely be repeated since the brain is programmed to continually seek
such pleasure. In hunter-gatherer societies, this reward system was
beneficial for survival and reproductive success. But now, when there
are fewer challenges to survival and reproducing, certain activities in
the present environment (gambling, drug use, eating) exploit this
system, leading to addictive behaviors.
Work stress
Examples
of evolutionary mismatch also occur in the modern workplace. Unlike our
hunter-gatherer ancestors who lived in small egalitarian societies the
modern work place is large, complex, and hierarchical. Humans spend
significant amounts of time interacting with strangers in conditions
that are very different from those of our ancestral past.
Hunter-gatherers do not separate work from their private lives, they
have no bosses to be accountable to, or no deadlines to adhere to. Our
stress system reacts to immediate threats and opportunities. The modern
workplace exploits evolved psychological mechanisms that are aimed at
immediate survival or longer-term reproduction. These basic instincts
misfire in the modern workplace, causing conflicts at work, burnout, job
alienation and poor management practices.
Gambling
There
are two aspects of gambling that make it an addictive activity: chance
and risk. Chance gives gambling its novelty. Back when humans had to
forage and hunt for food, novelty-seeking was advantageous for them,
particularly for their diet. However, with the development of casinos,
this trait of pursuing novelties has become disadvantageous. Risk
assessment, the other behavioral trait applicable to gambling, was also
beneficial to hunter-gatherers in the face of danger. However, the types
of risks hunter-gatherers had to assess are significantly different and
more life-threatening than the risks people now face. The attraction to
gambling stems from the attraction to risk and reward related activity.
Drug addiction
Herbivores have created selective pressure for plants to possess specific molecules that deter plant consumption, such as nicotine, morphine, and cocaine.
Plant-based drugs, however, have reinforcing and rewarding effects on
the human neurological system, suggesting a "paradox of drug reward" in
humans.
Human behavioral evolutionary mismatch explains the contradiction
between plant evolution and human drug use. In the last 10,000 years,
humans found the dopaminergic system, or reward system, particularly useful in optimizing Darwinian fitness.
While drug use has been a common characteristic of past human
populations, drug use involving potent substances and diverse intake
methods is a relatively contemporary feature of society. Human ancestors
lived in an environment that lacked drug use of this nature, so the
reward system was primarily used in maximizing survival and reproductive
success. In contrast, present-day humans live in a world where the
current nature of drugs render the reward system maladaptive. This class
of drugs falsely triggers a fitness benefit in the reward system,
leaving people susceptible to drug addiction. The modern-day dopaminergic system presents vulnerabilities to the difference in accessibility and social perception of drugs.
Eating
In the
era of foraging for food, hunter-gatherers rarely knew where their next
meal would come from. As a result, filling their stomachs up with lots
of food was advantageous since food was scarce. Intense consumption of
high-energy foods was selected for when the availability of food was low
and it was more difficult to find. Now, food is readily available, and
the neurological system that once helped people recognize the survival
advantages of essential eating has now become disadvantageous as it
promotes overeating. This has become especially dangerous after the rise
of processed foods, as the popularity of foods that have unnaturally
high levels of sugar and fat has significantly increased.
Non-human examples
Evolutionary
mismatch can occur any time an organism is exposed to an environment
that does not resemble the typical environment the organism adapted in.
Due to human influences, such as global warming and habitat destruction,
the environment is changing very rapidly for many organisms, leading to
numerous cases of evolutionary mismatch.
Examples with human influence
Sea turtles and light pollution
Female sea turtles
create nests to lay their eggs by digging a pit on the beach, typically
between the high tide line and dune, using their rear flippers.
Consequently, within the first seven days of hatching, hatchling sea
turtles must make the journey from the nest back into the ocean. This
trip occurs predominantly at night in order to avoid predators and
overheating.
Hatchling sea turtles must make their way back into the ocean.
In order to orient themselves towards the ocean, the hatchlings depend on their eyes to turn towards the brightest direction.
This is because the open horizon of the ocean, illuminated by celestial
light, tends to be much brighter in a natural undeveloped beach than
the dunes and vegetation.
Studies propose two mechanisms of the eye for this phenomenon. Referred
to as the "raster system", the theory is that sea turtles' eyes contain
numerous light sensors which take in the overall brightness information
of a general area and make a "measurement" of where the light is most
intense. If the light sensors detect the most intense light on a
hatchling's left side, the sea turtle would turn left. A similar
proposal called the complex phototropotaxis system theorizes that the
eyes contain light intensity comparators that take in detailed
information of the intensity of light from all directions. Sea turtles
are able to "know" that they are facing the brightest direction when the
light intensity is balanced between both eyes.
This method of finding the ocean is successful in natural
beaches, but in developed beaches, the intense artificial lights from
buildings, light houses, and even abandoned fires overwhelm the sea
turtles and cause them to head towards the artificial light instead of
the ocean. Scientists call this misorientation. Sea turtles can also
become disoriented and circle around in the same place.
Numerous cases show that misoriented hatchling sea turtles either die
from dehydration, get consumed by a predator, or even burn to death in
an abandoned fire. The direct impact of light pollution
on the number of sea turtles has been too difficult to measure.
However, this problem is exacerbated because all species of sea turtles
are endangered. Other animals, including migratory birds and insects,
are also victims to light pollution because they also depend on light
intensity at night to properly orient themselves.
Dodo bird and hunting
Dodo birds became completely extinct due to hunting.
The Dodo bird lived on a remote Island, Mauritius,
in the absence of predators. Here, the Dodo evolved to lose its
instinct for fear and the ability to fly. This allowed them to be easily
hunted by Dutch sailors who arrived on the island in the late 16th
century. The Dutch sailors also brought foreign animals to the island
such as monkeys and pigs that ate the Dodo bird's eggs, which was
detrimental to the population growth of the slow breeding bird.
Their fearlessness made them easy targets and their inability to fly
gave them no opportunity to evade danger. Thus, they were easily driven
to extinction within a century of their discovery.
The Dodo's inability to fly was once beneficial for the bird
because it conserved energy. The Dodo conserved more energy relative to
birds with the ability to fly, due to the Dodo's smaller pectoral
muscles. Smaller muscle sizes are linked to lower rates of maintenance
metabolism, which in turn conserves energy for the Dodo.
Lacking an instinct for fear was another mechanism through which the
Dodo conserved energy because it never had to expend any energy for a
stress response. Both mechanisms of conservation of energy was once
advantageous because it enabled the Dodo to execute activities with
minimal energy expenditure. However, these proved disadvantageous when
their island was invaded, rendering them defenseless to the new dangers
that humans brought.
Peppered moths during the English Industrial Revolution
Before the English Industrial Revolution of the late 18th and early 19th centuries the most common phenotypic color of the peppered moth
was white with black speckles. However, that changed when the
Industrial Revolution produced high levels of pollution. Due to the
Industrial Revolution the trees blackened in urban regions, causing the
original phenotype to stand out significantly more to predators.
Natural selection then began favoring the rare dark peppered carbonaria
moth in order for the species to camouflage and prevent attacks. The
dark moth's population expanded rapidly and by the 1950s vast amounts of
England saw carbonaria frequencies rise above 90%. The once favorable white speckled phenotype quickly became mismatched in the new environment.
However, in the late 1900s, the English made efforts to reduce
air pollution, causing the trees to turn back to their normal shade. The
change in color led the dark skin phenotype to revert from beneficial
to disadvantageous. Once again, the moth was not able to adapt fast
enough to the changing environment and thus the carbonaria phenotype
became mismatched. Since the trees' return to their natural color caused
the original phenotype to become advantageous again since it allowed
the peppered moth to hide from predators.
Giant jewel beetle and beer bottles
The Jewel Beetle has a shiny, brown exterior similar to that of a beer bottle
Evolutionary mismatch can also be seen among insects. One such example is in the case of the Giant Jewel Beetle (Julodimorpha bakewelli).
The male jewel beetle has evolved to be attracted to certain features
of the female jewel beetle that allow the male jewel beetle to identify a
female as it flies across the desert.
These features include size, color, and texture. However, these
physical traits are seen manifested in beer bottles as well. As a
result, male jewel beetles often consider beer bottles more attractive
than female jewel beetles due to the beer bottle's large size and
attractive coloring.
Beer bottles are often discarded by humans in the Australian desert
that the jewel beetle thrives in, creating an environment where male
jewel beetles prefer to mate with beer bottles instead of female jewel
beetles. This is a situation that is extremely disadvantageous as it
reduces the reproductive output of the jewel beetle as fewer beetles are
mating. This condition can be considered an evolutionary mismatch, as a
habit that evolved to aid in reproduction has become disadvantageous
due to the littering of beer bottles, an anthropogenic cause.
Examples without human influence
Information cascades between birds
A group of Nutmeg Mannikins at a bird feeder
Normally, gaining information from watching other organisms allows the observer to make good decisions without spending effort.
More specifically, birds often observe the behavior of other organisms
to gain valuable information, such as the presence of predators, good
breeding sites, and optimal feeding spots.
Although this allows the observer to spend less effort gathering
information, it can also lead to bad decisions if the information gained
from observing is unreliable. In the case of the nutmeg mannikins, the
observer can minimize the time spent looking for an optimal feeder and
maximize its feeding time by watching where other nutmeg mannikins feed.
However, this relies on the assumption that the observed mannikins also
had reliable information that indicated the feeding spot was an ideal
one. This behavior can become maladaptive when prioritizing information
gained from watching others leads to information cascades,
where birds follow the rest of the crowd even though prior experience
may have suggested that the decision of the crowd is a poor one. For instance, if a nutmeg mannikin sees enough mannikins feeding at a feeder,
nutmeg mannikins have been shown to choose that feeder even if their
personal experience indicates that the feeder is a poor one.
House finches and the introduction of the MG disease
Evolutionary mismatch occurs in house finches
when they are exposed to infectious individuals. Male house finches
tend to feed in close proximity to other finches that are sick or
diseased, because sick individuals are less competitive than usual, in
turn making the healthy male more likely to win an aggressive
interaction if it happens. To make it less likely to lose a social
confrontation, healthy finches are inclined to forage near individuals
that are lethargic or listless due to disease. However, this disposition has created an evolutionary trap for the finches after the introduction of the MG disease
in 1994. Since this disease is infectious, healthy finches will be in
danger of contraction if they are in the vicinity of individuals that
have previously developed the disease. The relatively short duration of
the disease's introduction has caused an inability for the finches to
adapt quickly enough to avoid nearing sick individuals, which ultimately
results in the mismatch between their behavior and the changing
environment.
Exploitation of earthworm's reaction to vibrations
Worm charming is a practice used by people to attract earthworms
out of the ground by driving in a wooden stake to vibrate the soil.
This activity is commonly performed to collect fishing bait and as a
competitive sport. Worms that sense the vibrations rise to the surface.
Research shows that humans are actually taking advantage of a trait that
worms adapted to avoid hungry burrowing moles which prey on the worms.
This type of evolutionary trap, where an originally beneficial trait is
exploited in order to catch prey, was coined the "rare enemy effect" by Richard Dawkins, an English evolutionary biologist.
This trait of worms has been exploited not only by humans, but by other
animals. Herring gulls and wood turtles have been observed to also
stamp on the ground to drive the worms up to the surface and consume
them.
Evolutionary psychiatry, also known as Darwinian psychiatry, is a theoretical approach to psychiatry that aims to explain psychiatric disorders in evolutionary terms. A branch of the field of evolutionary medicine, it is distinct from the medical practise of psychiatry in its emphasis on providing scientific explanations rather than treatments for mental disorder. This often concerns questions of ultimate causation. For example, psychiatric genetics
may discover genes associated with mental disorders, but evolutionary
psychiatry asks why those genes persist in the population. Other core
questions in evolutionary psychiatry are why heritable mental disorders
are so common how to distinguish mental function and dysfunction, and whether certain forms of suffering conveyed an adaptive advantage. Disorders commonly considered are depression, anxiety, schizophrenia, autism, eating disorders, and others. Key explanatory concepts are of evolutionary mismatch (when modern environments cause mental health conditions) and the fact that evolution is guided by reproductive success rather than health or wellbeing.
Rather than providing an alternative account of the cause of mental
disorder, evolutionary psychiatry seeks to integrate findings from
traditional schools of psychology and psychiatry such as social psychology, behaviourism, biological psychiatry and psychoanalysis into a holistic account related to evolutionary biology. In this sense, it aims to meet the criteria of a Kuhnianparadigm shift.
Though heavily influenced by evolutionary psychology,
as Abed and St. John-Smith noted in 2016, "Unlike evolutionary
psychology, which is a vibrant and thriving sub-discipline of academic
psychology with a strong and well-funded research programme,
evolutionary psychiatry remains the interest of a small number of
psychiatrists who are thinly scattered across the world." It has gained
increasing institutional recognition in recent years, including the
formation of an evolutionary psychiatry special interest group within
the Royal College of Psychiatrists and the Section on Evolutionary Psychiatry within the World Psychiatric Association, and has gained traction with the publication of texts aimed at the popular audience such as 'Good Reasons for Bad Feelings: Insight from the Frontier of Evolutionary Psychiatry' by Randolph Nesse.
History
The
pursuit of evolutionary psychiatry in its modern form can be traced to
the late 20th century. A landmark text was George Williams and Randolph Nesse’s ‘Why We Get Sick: The New Science of Darwinian Medicine’
(which could also be considered as marking the beginning of
evolutionary medicine), the publication of ‘Evolutionary Psychiatry: A
New Beginning’ by John Price and Anthony Stevens and others. However,
the questions which evolutionary psychiatry concerns itself with have a
longer history, for instance being recognised by Julian Huxley and Ernst Mayr in an early paper considering possible evolutionary explanations for what has become known as the ‘schizophrenia paradox’.
Concepts applied by modern evolutionary psychiatry to explain
mental disorder are also much older than the field, in many cases.
Psychological suffering as an inevitable, and sometimes useful, part of
human existence has been long-recognised, and the idea of divine madness pervades ancient societies and religions. Cesare Lombroso,
a pioneering psychiatrist, began utilising evolutionary theory to
explain mental disorder as early as 1864, proposing that insanity was
the price of genius, as human brains had not evolved with the capacity
to become hyper-intelligent and creative and yet remain sane.
Darwin applied evolutionary theory to explain psychological traits and
emotions, and recognised the usefulness of studying mental disorders in
pursuit of understanding natural psychological function. Freud was
heavily influenced by Darwinian theory, and towards the end of his life
recommended psychoanalysts should study evolutionary theory. Bowlby's attachment theory was developed in explicit reference to evolutionary theory.
In 2016 the Evolutionary Psychiatry Special Interest Group (EPSIG) was set up in the Royal College of Psychiatrists, UK by Riadh Abed and Paul St-John Smith. It is now the largest global institution for connecting psychiatrists and researchers interested in evolutionary psychiatry with over 1700 members. It has run several seminars and meetings dedicated to evolutionary psychiatry, hosting lectures by prominent academics such as Simon Baron-Cohen and Robin Dunbar. All of the meetings are available on the EPSIGUK YouTube channel. EPSIG also publishes regular newsletters,
organising conferences, conducting interviews and hosting special
essays related to evolutionary psychiatry (for which there is not yet a
dedicated academic journal). As Riadh Abed, (previous chair) stated in a
newsletter "Our aims are both big and radical: they are for evolution
to be accepted as the overarching framework for psychiatry and for
evolution to take centre stage in our understanding of mental health and
mental disorder."
Psychological function and dysfunction
Mental disorders are often defined by ‘dysfunction’ in psychiatric manuals such as the DSM, without a precise definition of what constitutes dysfunction, allowing any mental state deemed socially unacceptable (such as homosexuality) to be considered dysfunctional, and thus a mental disorder.
Evolutionary theory is uniquely placed to be able to distinguish biological function from dysfunction by evolutionary processes. Unlike the objects and processes of physics and chemistry, which cannot strictly be said to be functioning nor dysfunctioning, biological systems are the products of evolution by natural selection,
and so their ‘function’ and ‘dysfunction’ can be related to that
evolutionary process. The concept of evolutionary function is tied to
the reproductive success brought about by phenotypes which caused genes
to be propagated. Eyes evolved to see – the function of the eyes is to
see – so dysfunctional eyes are those that cannot see. This sense of
function is defined by the evolutionary history of eyesight providing
reproductive success, not current cultural opinions of normality and
abnormality on which common conceptions of health and disorder often
depend.
Jerome Wakefield's influential ‘Harmful Dysfunction’ definition of
disorder utilises evolutionarily selected effects to ground the concept
of ‘dysfunction’ in the objective process of evolution. Wakefield
proposes that mental disorder must be both harmful, in a value-defined
sense, and dysfunctional, in an evolutionary sense.
This grounding of dysfunction in an objective historical process
is important in the context of psychiatry's history of labelling
socially undesirable mental states and traits as ‘disorders’, such as
female masturbation and homosexuality. Current diagnostic manuals are
decided by consensus. For example, in 1973 the APA called a vote to
reconsider homosexuality's status as a mental disorder. By a 58%
majority, it was struck off. The category of borderline personality disorder was created upon the basis of a single paper and consensus between about a dozen psychiatrists. In 2014 psychiatrists voted on the features of a new disorder, internet gaming disorder. The reliance on votes and expert consensus rather than objective evidence or biomarkers
is a longstanding criticism of psychiatry that evolutionary psychiatry
can avoid by adopting the evolutionary definition of dysfunction.
Evolutionary causation and Tinbergen’s four questions
The research questions and concerns of evolutionary medicine and psychiatry can be distinguished from normal biomedicine and biological-psychiatry research as asking ultimate instead of proximate questions. This ultimate-proximate distinction was introduced by Ernst Mayr
to identify different levels of causational explanation: proximate
explanations refer to mechanistic biological processes (e.g. genes,
ontogenetic development, hormones, neurological structure and function)
whilst ultimate explanations ask about the evolutionary process of
natural selection which led to these biological structures and processes
functioning as observed. This could be conceived of as proximate
explanations are ‘how’ questions whilst ultimate explanations are ‘why’
questions.
Niko Tinbergen further deconstructed this ultimate-proximate distinction into his ‘four questions’. These questions of mechanism, ontogeny, function and phylogeny
can be asked of any single trait or disorder (often behavioural,
although not necessarily) to identify the different questions of
causation which are simultaneously relevant.
Proximate questions can be separated into questions of mechanism, which concerns how the trait works, the structure and process of its biological mechanism, and questions of ontogeny or individual development which concerns how the trait develops in an individual.
Ultimate questions can be either of or evolutionary function or adaptive value , which concerns how the trait influenced fitness throughout evolutionary history; and questions of phylogeny or evolution, which concern the history of a trait down the phylogenetic tree.
To take the example of depression, we can ask about proximate
mechanisms (e.g. neurotransmitter properties), ontogenetic development
(e.g. neurological development over an individual's lifespan), adaptive
function (e.g. low mood system) and phylogeny (e.g. apparent low mood in
reaction to social defeat in primates).
Key explanatory concepts in evolutionary psychiatry
Mental
disorder results from many different environmental and genetic causes,
with various complex neurological correlates – but evolutionary medicine recognises several general principles which allow vulnerability to disorder. Adapted from Nesse (2019), Stearns (2016) and Gluckman (2016).
Reproductive success over health
Natural selection acts on reproductive fitness,
not biological states which are what may be considered healthy; healthy
states are only selected if they also have positive effects on health.
This is used in evolutionary medicine
to explain aging and diseases of senescence: diseases which appear past
reproductive age have minimal effect on fecundity. Psychological
suffering and various cognitive states which may seem unhealthy or
disorderly may equally be products of evolutionary processes if they
increased reproductive success. Evidence of this may be seen in
disorders associated with substantial apparent dysfunction, yet average
levels of fertility.
Mismatch
Evolutionary mismatch
occurs when evolved traits become maladaptive due to changes in the
environment. This is a common factor causing evolutionary change (e.g.
in the peppered moth) and is relevant to medicine when the mismatched
traits cause problems affecting health. Psychiatric conditions may in
some cases be evolved states which we are misinterpreting as disorders
because they no longer fit our social expectations; or they may be
mental states or traits which would manifest healthily in ancestral
environments, but become pathological due to some feature of modern
environments. Evidence of mismatch is most prominent when comparing
traditional-living humans to modern-living humans or when new
environmental factors arise which clearly cause disease (e.g. the
availability of cheap, high calorie foods causing obesity).
Defences
Psychological responses such as fear and panic are adaptive in many situations,
especially of imminent danger, and seen in multiple species. Certain
mental disorders may result from such responses, either as a maladaptive
overactivation of the response, or as an adaptive process which is
specifically tuned to over-activate because the fitness cost of the
response is outweighed by the fitness benefit – called the smoke
detector principle.
The fact that such experiences are highly distressing, debilitating and
inappropriate leads to their diagnosis as mental disorders.
Mutation-selection balance
Natural selection acts upon genetic mutations, which are present in every generation, removing those which reduce fitness
and increasing the prevalence of those which improve fitness. Mutations
are also more likely to reduce fitness than improve it. Biological
traits with a large mutational target size, such as brains, where over
80% of the genome is expressed,
are especially likely to be suspect to harmful mutations which
negatively affect cognitive function, which are then removed by natural
selection. Such mutations are often associated with intellectual
disability, certain cases of autism, schizophrenia,
and many more disorders. The fact that de-novo mutations cause such
disorders in a few cases has been used to argue that the other cases are
caused by as-yet undiscovered disease processes, although the presence
of heterogeneity within disorder categories and the lack of discovered pathology despite significant work in neuroscience and genetics is evidence against that view.
Schizophrenia is primarily characterized by psychosis (hallucinations and delusions)
and symptoms of cognitive debilitation such as erratic speech, lost
interest in normal activities and disordered thinking. It is the most
extreme condition of the schizophrenia or psychosis spectrum, which includes schizotypy
and other psychotic disorders, arguably extending to unusual
experiences such as perceiving ghosts or believing in magic which are
common in the population.
Schizophrenia is a heritable condition, prevalent in slightly
less than 1% of the population, with negative effects of fecundity,
especially in men.
Because of this, it was perhaps the first psychiatric condition
explicitly raised as specifically requiring an evolutionary explanation,
in the so-called ‘schizophrenia paradox’ (now more generally known as
the paradox of common, harmful, heritable mental disorders). To explain schizophrenia's persistence various evolutionary hypotheses have been made.
Hypotheses of schizophrenia as a true dysfunction are plentiful.
It has been hypothesised that schizophrenia is a dysfunctional byproduct
of human evolution for language and brain hemisphere lateralization, or a dysfunction of the social brain, or related to theory-of-mind. Other theories have referred to the possibility it is caused by mutation-selection balance. However, the expected rare and de novo mutations have only been found in a small proportion of cases.
Many alleles predisposing to schizophrenia are common in the
population, making adaptive hypotheses plausible, as has been noted
since the mid 20th century.
Hypotheses explaining schizophrenia as resulting from adaptation
vary widely. Early theorists proposed it conveyed improvements to the immune system or illness recovery or facilitates group-splitting. Inspired by the longstanding cultural ideas of madness as related to genius, Nettle proposed that schizotypy could be related to creative success,
which added to mating success, and that the positive effects of
schizotypal traits might be an explanation for why these traits persist.
However, the measured fecundity benefit of such traits has been found
to not outweigh the cost of schizophrenia via inclusive fitness
(although this may be due to selection bias).
The shamanism hypothesis of schizophrenia states that in
traditional societies the experience of psychosis facilitated the
induction of shamans
(magico-religious practitioners such as medicine men, diviners, witch
doctors, exorcists and mediums). Shamanism is a common feature of human
societies, with certain individuals deemed to have a particular
connection to the supernatural world which gives them the ability to
perform magic, especially healing. This in particular is used explain
the common religious and grandiose content of psychotic experiences and
the belief in supernatural powers, which may have been believed rather
than disbelieved in traditional societies. The onset of schizophrenia
also closely resembles shamanic initiations, which often feature
hallucinations, delusions and incoherent speech. Possible links between
shamanism and insanity have been recognised for many decades by
anthropologists (e.g. "...mentally ill people are often regarded as holy
in primitive societies" and "Feeblemindedness is treated with scorn in Niue today, but insanity still calls forth respect") but the most recent iteration of the theory is by Joseph Polimeni,
who argues that shamans facilitate group functioning, and so psychosis
evolved as a result of group selection. Critics have argued that the
trance states and self-control exhibited by shamans are unlike the
characteristics of schizophrenia.
Autism spectrum disorder
is characterized by difficulties with social interaction and
communication, and restricted and repetitive behavior. In developed
countries, about 1.5% of children are diagnosed with ASD as of 2017, up from 0.7% in 2000 in the United States. It is diagnosed four-to-five times more often in males than females.
Autism differs widely between individuals (it is highly heterogenous) with different causes for different individuals. Some cases are caused by deleterious mutations or prenatal and neonatal trauma, for which no adaptive explanation is required. These cases are often associated with intellectual disability.
Estimates range that between 5-20% of the autism spectrum can be
explained by these dysfunctional processes, especially of genetics.
However, other cases of autism are eligible for adaptive explanations.
The fact that multiple explanations for autism exist causes conflict
within the autism community, especially between proponents of the neurodiversity perspective and family members caring for severely disabled autistic individuals.
The idea of autism as conveying cognitive strengths has become steadily more popular since the film Rain Man and the recent growth of the neurodiversity and autism rights movements, although recognition of unusual autistic ability be found even in the early writings of Hans Asperger who called his autistic patients 'little professors'. It has been suggested by autistics such as Temple Grandin that autistic hunter-gatherer ancestors were important figures in the community, especially for their inventive capacity:
'Who
do you think made the first stone spear? (...) That wasn't the yakkity
yaks sitting around the campfire. It was some Asperger sitting in the
back of a cave figuring out how to chip rocks into spearheads. Without
some autistic traits you wouldn't even have a recording device to record
this conversation on."
Leading autism researcher Simon Baron-Cohen has proposed that autism is an extreme systemising cognitive type,
on an empathising-systemising spectrum which all people fall onto,
somewhat related to the things-people dimension of interests. He
recognised the exceptional talent of many autistic people in some area
of non-human knowledge or skill. In his book, "The Pattern Seekers: how autism drives human invention",
he proposes a theory of human inventiveness that places autistic
individuals as having extreme versions of these inventing (or
systemising) traits.
Marco del Giudice has suggested autistic-like traits in their
non-pathological form contribute to a male-typical strategy geared
toward high parental investment, low-mating effort, and long-term
resource allocation. He has also related this to a slow life history strategy.
This is based on the fact that autistics show lower interest in
short-term mating, higher partner-specific investment, and stronger
commitment to long-term romantic relations.
Bernard Crespi has suggested that autism is a disorder of high intelligence,
noting that autism commonly involves enhanced, but imbalanced,
components of intelligence. This hypothesis is supported by evidence
showing that autism and high IQ
share a diverse set of convergent correlates, including large brain
size, fast brain growth, increased sensory and visual-spatial abilities,
enhanced synaptic functions, increased attentional focus, high
socioeconomic status, more deliberative decision-making, profession and
occupational interests in engineering and physical sciences, and high
levels of positive assortative mating. Recent evolutionary selection
pressures for high intelligence in humans have therefore conveyed autism
risk.
Psychopathy
Psychopathy
(sometimes known as sociopathy or antisocial personality disorder), is
characterised by deceitfulness, lack of empathy and guilt,
impulsiveness, and antisocial behaviour. The prevalence of psychopathy in the general population is estimated to be around 1%, and 20% in prison populations with higher rates in North America than Europe. Psychopathy, narcissism and Machiavellianism are considered to be part of the Dark Triad, traits that are generally characterised by selfishness and low agreeableness.
Various evolutionary hypotheses have been proposed to explain
psychopathy and the Dark Triad. Within an ancestral context, high
self-interest and low levels of empathy could function as a short-term
mating strategy. There is evidence that Dark Triad traits are positively
correlated with the number of sexual partners, more unrestrictive sociosexuality and preference for short-term mates.
Glenn et al. stated two theories on how selection might allow for psychopathic traits. The first is as a fast life-history strategy, associated with less focusing on the future, high risk taking and short-term mating. The second is mutation-selection balance, with many common alleles
of small effect selected against, which, when accumulated, can result
in psychopathic behaviour, without any significant disruption of reproductive fitness.
Mealey's influential account states that psychopaths are designed for social deception and evolved
to pursue manipulative life strategies or cheating strategies,
(reflected in cheater-cooperation models of game theory).
Cheating strategies are stable at low frequencies in the population,
but will be detected and punished at higher frequencies. This frequency-dependent strategy would explain the prevalence of psychopathic traits in the population.
Mealey makes four statements about psychopathy:
There is a genetic predisposition for psychopathy, which is normally distributed in all populations.
A few individuals will be deemed "morally insane" in any culture, due to selection filling in this small and frequency-dependent niche.
Depending on environmental conditions, individuals who are less
extreme on the continuum will pursue a similar cheating strategy.
An underlying genetic continuum of psychopathy is present in all of
us, becoming apparent when antisocial strategies are more profitable in
certain conditions.
Mealey
also explains the higher male prevalence and predisposing environmental
factors (low physical attractiveness, age, health, physical
attractiveness, intelligence, socioeconomic status, and social skills)
as signals that a cheating strategy is preferable, hence why these
factors are associated with psychopathic traits.
Major depressive disorder
(MDD) is characterized by at least two weeks of persistent low mood. It
is accompanied by a wide variety of negative feelings such as low self-esteem,
loss of interest in normally enjoyable activities and low energy. There
are multiple possible evolutionary explanations for the occurrence of
depression and low mood in humans. Many different hypotheses are not mutually exclusive. It has been suggested that different life events and other disease processes are responsible for different forms of depression
with subtypes related to infection, long-term stress, loneliness,
traumatic experience, hierarchy conflict, grief, romantic rejection,
postpartum events, the season, chemicals, somatic diseases and
starvation. Individualising treatment based on causational subtypes is
suggested as lending direction in treatments. Other hypotheses include:
Social-oriented hypotheses
The social competition hypothesis (similarly to the social rank theory)
interprets depression as an emotion of submission, an involuntary
strategy to create a subjective sense of incapacity. Feelings of
powerlessness or helplessness cause this incapacity, inhibiting
aggression towards higher-ranked people and signalling submission. Low
mood encourages acceptance of a loss in rank and promotes yielding. John
Price endorsed this theory, noting that chickens who lose a fight
withdraw from social engagement and act submissively, reducing further
attacks by chickens higher in the hierarchy and avoiding being wounded
or even killed.
Similar to the social competition hypothesis, the 'social risk
hypothesis' states that depression prevents people engaging in social
interactions which might lead to them being ostracised. This hypothesis
is inspired by risk-sensitive foraging. It suggests that people in successful social relationships
can tolerate higher levels of social risk-taking, while on the other
hand, people with low social standing cannot. The theory suggests that
the low mood which accompanies MDD exists in order to reduce potential
risk taking and encourages isolation in those individuals.
Psychic pain hypotheses
Depression
is common in people who are pursuing unreachable goals and depression
might be a manifestation, similarly to the social competition
hypothesis, of a failure to yield.
Low mood increases an organism's ability to cope with the adaptive
challenges characteristic of unpropitious situations. Pessimism and lack
of motivation may give a fitness advantage by inhibiting certain
actions. When current life plans are not working, the distress and lack
of motivation that characterize depression may motivate planning and
reassessment or escape, even by suicide.
Feelings of sadness and discouragement may be a useful stimulus to
consider ways of changing the situation, by disengagement of motivation
from an unreachable goal. In nature, it would make sense to decrease
motivation in situations where taking action would be futile and
therefore a waste of resources. Therefore, low mood in those situations
would help the individual to preserve energy. This hypothesis is
inspired by the marginal value theorem.
The 'analytical rumination' hypothesis is a refinement of the
psychic pain hypothesis. It suggests that depressive symptoms are
triggered by complex problems and an inability to find the correct
course of action. This theory describes how this could lead to a loss of
interest in virtually all activities in order to benefit the individual
to single-mindedly focus on the problem at hand.
Cry-for-help and bargaining hypotheses
Depression, deliberate self-harm and suicide
may be reactions to life circumstances that encourage others to provide
resources and help to the depressed or suicidal individual. Group
members, and especially family members, have a vested interest in
keeping the depressed individual alive and changing their circumstances
in such a way as to make them a functioning member of society again. It
may be the case that certain life choices (e.g. marrying somebody who
your parents dislike) may become possible only when depressed or
suicidal behaviour is observed by the family or social group. This could explain various precipitating factors for depression.
However, some research has found that signs of depression only lead to a
short-term increase of care by family members, after which they tend to
withdraw.
Eating disorders
Evolutionary perspectives exist on Anorexia nervosa (henceforth ‘anorexia’) and Bulimia nervosa
(henceforth ‘bulimia’). Anorexia is characterized by restriction of
food intake, bulimia by cycles of binging (excessive eating) and purging
(forced removal of the food). Both are associated with body shape and physical attractiveness concerns.
The Sexual Competition Hypothesis
relates eating disorders to body shape and physical appearance as of
adaptive function in human females (who are highly over-represented in
eating disorders): eating disorders are supposed to increase female
attractiveness. Some evidence from non-clinical and clinical populations
support this hypothesis. They apply the framework of life-history theory,
proposing anorexia as a slow life history strategy whilst bulimia is a
fast strategy. Both studies had their limitations and it was further
mentioned that the deep structures of eating disorders may not be
reflected by their current classifications.
An alternative account comes from Nesse.
Recognising that many anorexia patients are neither actively chasing
men nor particularly interested in sex, and that eating disorders became
more common in the second half of the 20th century,
he argues eating disorders are new problems with no redeeming features.
They are caused by increasingly high concerns about appearance linked
with the possibility in modern societies to compare someone's appearance
to thousands of others instantly. Glorification of unrealistic body
types in media, as well as increased availability of sex, may contribute
to this. He does, however, acknowledge that intra-sexual competition is a driving force of anorexia and bulimia in undergraduate women.
Obesity is not an eating disorder in any classification system, though it is established that overweight and obesity in particular is connected with various diseases,
and an evolutionary perspective can explain the tendency towards
overeating. The human body has evolved to cope with the environments of
scarcity, selecting for beneficial adaptations of hunger and eating. Fat
storage allows preparation for future food shortages. In a case of mismatch,
modern environments have cheap, readily available food, and very few
times of scarcity. Kardum et al. also elaborated the differences in
nutrient composition in modern and ancestral societies to illustrate the
challenge modern diet imposes on the not-yet adapted human body and
genotype.
Anxiety
Anxiety is a feeling of worry, unpleasantness and dread towards possible future events and exists to protect us from dangers. In the US, anxiety disorders are the most common mental illness, with around 29% of adults expected to suffer from any anxiety disorder in their lifetime. Women are disproportionately affected.
Evolutionary perspectives on anxiety disorders generally consider
the adaptive function of the emotion of normal anxiety, and reasons
this adaptive system may manifest in the various types of anxiety
disorder.
A key evolutionary explanation for anxiety disorder is the Smoke Detector Principle.
It is often preferable to overactive anxiety in dangerous situations,
in the same way a smoke detector is designed to overactivate. Randolph
Nesse writes:
“You are thirsty on the ancient African
savanna and a watering hole is just ahead, but you hear a noise in the
grass. It could be a lion, or it might just be a monkey. Should you
flee? It depends on the costs. Assume that fleeing in panic costs 100
calories. Not fleeing costs nothing if it is only a monkey, but if the
noise was made by a lion, the cost is 100’000 calories - about how much
energy a lion would get from having you for lunch!”
Evolutionary
psychiatry has so far primarily concentrated on scientific explanations
for mental disorders rather than developing novel treatment approaches.
However, there are various consequences of taking an evolutionary
perspective on mental disorder for treatment decisions, at an individual
and public health level, which make evolutionary psychiatry an
important field of future research and application.
Evolutionary explanations for disorders which reframe them as mismatched
or otherwise costly adaptations may be taken to imply that treatment is
unnecessary – but this is not the view of evolutionary psychiatrists –
and is the same mistake made by those who believe evolutionary biology
means endorsing eugenics, a version of the naturalistic fallacy – that what is natural (in this case, evolved) is good. Many medical interventions are ‘unnatural’ in this sense (e.g. contraception and anaesthetic). The explanations of evolutionary psychiatry have no inherent value in directing treatment. Randolph Nesse writes:
"On
learning that low mood can be useful, some people conclude that it
therefore should not be treated. This mistake is like the one that arose
when anethesia was first invented: some doctors refused to use it, even
during surgery, because, they said, pain is normal. We must not let new
understanding of the utility of low mood interfere with our efforts to
relieve mental pain."
Although evolutionary explanations may not affect the necessity for
treatment, they can be directive or supportive of treatment, or make
current treatment strategies more effective. Proposed benefits of taking
an evolutionary perspective on mental disorders have largely come from
integrating evolutionary explanations into psychotherapy. Bailey and Gilbert write:
"The
evolutionary approach helps to answer three fundamental questions about
humanity that go to the heart of professional helping and clinical
practice: First, what and who are we as human beings – that is, what is
human nature or species ‘normality’?; second, how and why do humans
develop and/or behave in less than optimal ways – that is, what can
evolution tell us about the causes of suffering and psychopathology?;
and, third, what can professional helpers and psychotherapists do to
ameliorate or even ‘cure’ the suffering of heart and mind?"
It has been suggested that patients are encouraged and destigmatised by hearing evolutionary explanations for their conditions,
with positive effects during cognitive behavioural therapy –
integration of knowledge of behavioural genetics, neuroscience and
evolutionary psychiatry into psychotherapy has been called ‘Informed
Cognitive Therapy’ by Mike Abrams. Abrams also proposes that recognising the inherited and somewhat immutable nature of certain traits (such as psychopathy and autism)
implies that therapists should not try and alter the traits
characteristics, but instead provide advice on how to best utilise these
cognitive types within the context of modern society. This aligns with
the aims and claims of the neurodiversity movement.
Evolutionary explanations for mental disorders, especially of mismatch, have connotations for public health measures and organisational psychology.
Disorders which are consequences of novel environments may be rectified
or prevented by implementing social structures which better replicate
ancestral environments. For example, postpartum depression
may be more likely in modern environments where single parents are
given sole responsibility in raising a child, which is highly unusual in
the context of an evolutionary history of alloparenting
and communal care. Reversing this mismatch, social services supporting
new mothers in parenting may prevent postpartum depression (see Evolutionary approaches to postpartum depression). Education
and employment environments which are particularly likely to cause
mental disorders may also be altered to better suit natural human
psychological capacities.
