Evolutionary public health: introducing the concept.

The emerging discipline of evolutionary medicine is breaking new ground in understanding why people become ill. However, the value of evolutionary analyses of human physiology and behaviour is only beginning to be recognised in the field of public health. Core principles come from life history theory, which analyses the allocation of finite amounts of energy between four competing functions-maintenance, growth, reproduction, and defence. A central tenet of evolutionary theory is that organisms are selected to allocate energy and time to maximise reproductive success, rather than health or longevity. Ecological interactions that influence mortality risk, nutrient availability, and pathogen burden shape energy allocation strategies throughout the life course, thereby affecting diverse health outcomes. Public health interventions could improve their own effectiveness by incorporating an evolutionary perspective. In particular, evolutionary approaches offer new opportunities to address the complex challenges of global health, in which populations are differentially exposed to the metabolic consequences of poverty, high fertility, infectious diseases, and rapid changes in nutrition and lifestyle. The effect of specific interventions is predicted to depend on broader factors shaping life expectancy. Among the important tools in this approach are mathematical models, which can explore probable benefits and limitations of interventions in silico, before their implementation in human populations.

Anorexia: A perverse effect of attempting to control the starvation response.

Starvation arouses evolved protective mechanisms including binge eating and increased metabolic efficiency and fat storage. When aroused by dieting, the experiences of out-of-control eating, increased appetite, and increased fat storage arouse greater fears of obesity, spurring renewed attempts to restrict intake severely. The resulting positive feedback cycle escalates into bulimia for many, and anorexia in a few.

Social selection is a powerful explanation for prosociality.

Cultural group selection helps explain human cooperation, but social selection offers a complementary, more powerful explanation. Just as sexual selection shapes extreme traits that increase matings, social selection shapes extreme traits that make individuals preferred social partners. Self-interested partner choices create strong and possibly runaway selection for prosocial traits, without requiring group selection, kin selection, or reciprocity.

Depression sum-scores don't add up: why analyzing specific depression symptoms is essential.

Most measures of depression severity are based on the number of reported symptoms, and threshold scores are often used to classify individuals as healthy or depressed. This method--and research results based on it--are valid if depression is a single condition, and all symptoms are equally good severity indicators. Here, we review a host of studies documenting that specific depressive symptoms like sad mood, insomnia, concentration problems, and suicidal ideation are distinct phenomena that differ from each other in important dimensions such as underlying biology, impact on impairment, and risk factors. Furthermore, specific life events predict increases in particular depression symptoms, and there is evidence for direct causal links among symptoms. We suggest that the pervasive use of sum-scores to estimate depression severity has obfuscated crucial insights and contributed to the lack of progress in key research areas such as identifying biomarkers and more efficacious antidepressants. The analysis of individual symptoms and their causal associations offers a way forward. We offer specific suggestions with practical implications for future research.

The status of evolutionary medicine education in North American medical schools.

BACKGROUND: Medical and public health scientists are using evolution to devise new strategies to solve major health problems. But based on a 2003 survey, medical curricula may not adequately prepare physicians to evaluate and extend these advances. This study assessed the change in coverage of evolution in North American medical schools since 2003 and identified opportunities for enriching medical education. METHODS: In 2013, curriculum deans for all North American medical schools were invited to rate curricular coverage and perceived importance of 12 core principles, the extent of anticipated controversy from adding evolution, and the usefulness of 13 teaching resources. Differences between schools were assessed by Pearson's chi-square test, Student's t-test, and Spearman's correlation. Open-ended questions sought insight into perceived barriers and benefits. RESULTS: Despite repeated follow-up, 60 schools (39%) responded to the survey. There was no evidence of sample bias. The three evolutionary principles rated most important were antibiotic resistance, environmental mismatch, and somatic selection in cancer. While importance and coverage of principles were correlated (r = 0.76, P < 0.01), coverage (at least moderate) lagged behind importance (at least moderate) by an average of 21% (SD = 6%). Compared to 2003, a range of evolutionary principles were covered by 4 to 74% more schools. Nearly half (48%) of responders anticipated igniting controversy at their medical school if they added evolution to their curriculum. The teaching resources ranked most useful were model test questions and answers, case studies, and model curricula for existing courses/rotations. Limited resources (faculty expertise) were cited as the major barrier to adding more evolution, but benefits included a deeper understanding and improved patient care. CONCLUSION: North American medical schools have increased the evolution content in their curricula over the past decade. However, coverage is not commensurate with importance. At a few medical schools, anticipated controversy impedes teaching more evolution. Efforts to improve evolution education in medical schools should be directed toward boosting faculty expertise and crafting resources that can be easily integrated into existing curricula.

Evolution in health and medicine Sackler colloquium: Making evolutionary biology a basic science for medicine.

New applications of evolutionary biology in medicine are being discovered at an accelerating rate, but few physicians have sufficient educational background to use them fully. This article summarizes suggestions from several groups that have considered how evolutionary biology can be useful in medicine, what physicians should learn about it, and when and how they should learn it. Our general conclusion is that evolutionary biology is a crucial basic science for medicine. In addition to looking at established evolutionary methods and topics, such as population genetics and pathogen evolution, we highlight questions about why natural selection leaves bodies vulnerable to disease. Knowledge about evolution provides physicians with an integrative framework that links otherwise disparate bits of knowledge. It replaces the prevalent view of bodies as machines with a biological view of bodies shaped by evolutionary processes. Like other basic sciences, evolutionary biology needs to be taught both before and during medical school. Most introductory biology courses are insufficient to establish competency in evolutionary biology. Premedical students need evolution courses, possibly ones that emphasize medically relevant aspects. In medical school, evolutionary biology should be taught as one of the basic medical sciences. This will require a course that reviews basic principles and specific medical applications, followed by an integrated presentation of evolutionary aspects that apply to each disease and organ system. Evolutionary biology is not just another topic vying for inclusion in the curriculum; it is an essential foundation for a biological understanding of health and disease.

Evolutionary psychiatry: foundations, progress and challenges.

Evolutionary biology provides a crucial foundation for medicine and behavioral science that has been missing from psychiatry. Its absence helps to explain slow progress; its advent promises major advances. Instead of offering a new kind of treatment, evolutionary psychiatry provides a scientific foundation useful for all kinds of treatment. It expands the search for causes from mechanistic explanations for disease in some individuals to evolutionary explanations for traits that make all members of a species vulnerable to disease. For instance, capacities for symptoms such as pain, cough, anxiety and low mood are universal because they are useful in certain situations. Failing to recognize the utility of anxiety and low mood is at the root of many problems in psychiatry. Determining if an emotion is normal and if it is useful requires understanding an individual's life situation. Conducting a review of social systems, parallel to the review of systems in the rest of medicine, can help achieve that understanding. Coping with substance abuse is advanced by acknowledging how substances available in modern environments hijack chemically mediated learning mechanisms. Understanding why eating spirals out of control in modern environments is aided by recognizing the motivations for caloric restriction and how it arouses famine protection mechanisms that induce binge eating. Finally, explaining the persistence of alleles that cause serious mental disorders requires evolutionary explanations of why some systems are intrinsically vulnerable to failure. The thrill of finding functions for apparent diseases is evolutionary psychiatry's greatest strength and weakness. Recognizing bad feelings as evolved adaptations corrects psychiatry's pervasive mistake of viewing all symptoms as if they were disease manifestations. However, viewing diseases such as panic disorder, melancholia and schizophrenia as if they are adaptations is an equally serious mistake in evolutionary psychiatry. Progress will come from framing and testing specific hypotheses about why natural selection left us vulnerable to mental disorders. The efforts of many people over many years will be needed before we will know if evolutionary biology can provide a new paradigm for understanding and treating mental disorders.

The EvMed Assessment: A test for measuring student understanding of core concepts in evolutionary medicine.

Background and objectives: Universities throughout the USA increasingly offer undergraduate courses in evolutionary medicine (EvMed), which creates a need for pedagogical resources. Several resources offer course content (e.g. textbooks) and a previous study identified EvMed core principles to help instructors set learning goals. However, assessment tools are not yet available. In this study, we address this need by developing an assessment that measures students' ability to apply EvMed core principles to various health-related scenarios. Methodology: The EvMed Assessment (EMA) consists of questions containing a short description of a health-related scenario followed by several likely/unlikely items. We evaluated the assessment's validity and reliability using a variety of qualitative (expert reviews and student interviews) and quantitative (Cronbach's α and classical test theory) methods. We iteratively revised the assessment through several rounds of validation. We then administered the assessment to undergraduates in EvMed and Evolution courses at multiple institutions. Results: We used results from the pilot to create the EMA final draft. After conducting quantitative validation, we deleted items that failed to meet performance criteria and revised items that exhibited borderline performance. The final version of the EMA consists of six core questions containing 25 items, and five supplemental questions containing 20 items. Conclusions and implications: The EMA is a pedagogical tool supported by a wide range of validation evidence. Instructors can use it as a pre/post measure of student learning in an EvMed course to inform curriculum revision, or as a test bank to draw upon when developing in-class assessments, quizzes or exams.

Towards a genuinely medical model for psychiatric nosology.

Psychiatric nosology is widely criticized, but solutions are proving elusive. Planned revisions of diagnostic criteria will not resolve heterogeneity, comorbidity, fuzzy boundaries between normal and pathological, and lack of specific biomarkers. Concern about these difficulties reflects a narrow model that assumes most mental disorders should be defined by their etiologies. A more genuinely medical model uses understanding of normal function to categorize pathologies. For instance, understanding the function of a cough guides the search for problems causing it, and decisions about when it is expressed abnormally. Understanding the functions of emotions is a foundation missing from decisions about emotional disorders. The broader medical model used by the rest of medicine also recognizes syndromes defined by failures of functional systems or failures of feedback control. Such medical syndromes are similar to many mental diagnoses in their multiple causes, blurry boundaries, and nonspecific biomarkers. Dissatisfaction with psychiatric nosology may best be alleviated, not by new diagnostic criteria and categories, but by more realistic acknowledgment of the untidy landscape of mental and other medical disorders.

Evolution at 150: time for truly biological psychiatry.

Darwin's On the Origin of Species was published 150 years ago, but evolution is just now being recognised as the missing half of a truly biological psychiatry. The general framework offered by an evolutionary perspective may be as valuable as its specific applications.

Evolution, emotions, and emotional disorders.

Emotions research is now routinely grounded in evolution, but explicit evolutionary analyses of emotions remain rare. This article considers the implications of natural selection for several classic questions about emotions and emotional disorders. Emotions are special modes of operation shaped by natural selection. They adjust multiple response parameters in ways that have increased fitness in adaptively challenging situations that recurred over the course of evolution. They are valenced because selection shapes special processes for situations that have influenced fitness in the past. In situations that decrease fitness, negative emotions are useful and positive emotions are harmful. Selection has partially differentiated subtypes of emotions from generic precursor states to deal with specialized situations. This has resulted in untidy emotions that blur into each other on dozens of dimensions, rendering the quest for simple categorically distinct emotions futile. Selection has shaped flexible mechanisms that control the expression of emotions on the basis of an individual's appraisal of the meaning of events for his or her ability to reach personal goals. The prevalence of emotional disorders can be attributed to several evolutionary factors.

An evolutionary medicine perspective on pain and its disorders.

Enormous progress in understanding the mechanisms that mediate pain can be augmented by an evolutionary medicine perspective on how the capacity for pain gives selective advantages, the trade-offs that shaped the mechanisms, and evolutionary explanations for the system's vulnerability to excessive and chronic pain. Syndromes of deficient pain document tragically the utility of pain to motivate escape from and avoidance of situations causing tissue damage. Much apparently excessive pain is actually normal because the cost of more pain is often vastly less than the cost of too little pain (the smoke detector principle). Vulnerability to pathological pain may be explained in part because natural selection has shaped mechanisms that respond adaptively to repeated tissue damage by decreasing the pain threshold and increasing pain salience. The other half of an evolutionary approach describes the phylogeny of pain mechanisms; the apparent independence of different kinds of pain is of special interest. Painful mental states such as anxiety, guilt and low mood may have evolved from physical pain precursors. Preliminary evidence for this is found in anatomic and genetic data. Such insights from evolutionary medicine may help in understanding vulnerability to chronic pain. This article is part of the Theo Murphy meeting issue 'Evolution of mechanisms and behaviour important for pain'.

How evolutionary psychiatry can advance psychopharmacology
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The prevailing paradigm for psychopharmacology focuses on understanding brain mechanisms as the key to finding new medications and improving clinical outcomes, but frustration with slow progress has inspired many pleas for new approaches. Evolutionary psychiatry brings in an additional basic science that poses new questions about why natural selection left us vulnerable to so many mental disorders, and new insights about how drugs work. The integration of neuroscience with evolutionary psychiatry is synergistic, going beyond reductionism to provide a model like the one used by the rest of medicine. It recognizes negative emotions as symptoms, that are, like pain and cough, useful defenses whose presence should initiate a search for causes. An integrative evolutionary approach explains why agents that block useful aversive responses are usually safe, and how to anticipate when they may cause harm. More generally, an evolutionary framework suggests novel practical strategies for finding and testing new drugs.
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El paradigma común para la psicofarmacología se centra en entender los mecanismos cerebrales como la clave para encontrar nuevos medicamentos y mejorar los resultados clínicos, pero la frustración con el lento progreso ha inspirado muchos motivos para nuevas aproximaciones. La psiquiatría evolutiva conlleva una ciencia básica adicional que plantea nuevas preguntas sobre el por qué la selección natural nos dejó vulnerables a tantos trastornos mentales y aporta nuevas perspectivas sobre cómo funcionan los fármacos. La integración de las neurociencias con la psiquiatría evolutiva es sinérgica, y va más allá del reduccionismo para proporcionar un modelo como el que utiliza el resto de la medicina. Reconoce las emociones negativas como síntomas, que son, como el dolor y la tos, defensas útiles cuya presencia debe iniciar una búsqueda de causas. Un enfoque evolutivo integrador explica por qué los agentes que bloquean las respuestas aversivas útiles suelen ser seguros y cómo anticipar cuándo pueden causar daño. De manera más general, un marco evolutivo sugiere nuevas estrategias prácticas para encontrar y probar nuevos medicamentos.

Le modèle prévalent de la psychopharmacologie se concentre sur la compréhension des mécanismes du cerveau comme la clé pour découvrir de nouveaux médicaments et améliorer les résultats cliniques, mais la frustration ressentie devant les lents progrès de cette méthode a inspiré de nombreux plaidoyers pour d'autres approches. La psychiatrie évolutionniste apporte une connaissance scientifique fondamentale supplémentaire qui pose de nouvelles questions sur la raison pour laquelle la sélection naturelle nous a laissé si vulnérables à tant de troubles mentaux, et des idées nouvelles sur la façon dont fonctionnent les médicaments. L'intégration de la psychiatrie évolutionniste aux neurosciences est source de synergies, allant bien au-delà du réductionnisme en fournissant un modèle semblable à celui utilisé par le reste de la médecine. Il reconnaît les émotions négatives comme des symptômes, exactement comme le sont la douleur et la toux, défenses habituelles qui doivent initier une recherche des causes. Une approche évolutionniste intégrative explique pourquoi des agents qui bloquent des réactions pertinentes d'aversion sont généralement sans danger, et comment anticiper lorsqu'ils pourraient causer un préjudice. Plus généralement, un modèle évolutionniste propose de nouvelles stratégies pratiques pour trouver et tester de nouveaux médicaments.

The state of evolutionary medicine in undergraduate education.

BACKGROUND AND OBJECTIVES: Undergraduate courses that include evolutionary medicine (EM) are increasingly available, but quantified data about such courses are lacking. In this article, we describe relevant course offerings by institution and department type, in conjunction with information on the backgrounds and experiences of associated instructors. METHODOLOGY: We searched course catalogs from 196 American universities to find courses that include EM, and sent a survey to 101 EM instructors to ask about their backgrounds and teaching experiences. RESULTS: Research-focused universities (R1) were much more likely to offer at least one course that covers evolutionary applications to health and disease than universities that granted only bachelor's or master's degrees. A survey course on EM was offered in 56% of 116 R1 universities, but only 2% of the 80 non-R1 universities we searched. Most EM instructors have backgrounds in anthropology or biology; each instructor's area of expertise provides clues as to how continued growth of EM may occur differently by discipline. CONCLUSIONS AND IMPLICATIONS: Undergraduates are most likely to learn about EM in research-intensive universities from an anthropological or biological perspective. Responses from anthropology and biology instructors, including whom they share course materials with, highlight that courses may differ depending on the discipline in which they are taught. LAY SUMMARY: Recognition of evolution's relevance to understanding health and disease is growing, but documentation of coverage in undergraduate education is lacking. This study explores where evolutionary medicine (EM) content is taught across 196 undergraduate institutions and how 53 instructors describe their experiences teaching EM.

Core principles of evolutionary medicine: A Delphi study.

BACKGROUND AND OBJECTIVES: Evolutionary medicine is a rapidly growing field that uses the principles of evolutionary biology to better understand, prevent and treat disease, and that uses studies of disease to advance basic knowledge in evolutionary biology. Over-arching principles of evolutionary medicine have been described in publications, but our study is the first to systematically elicit core principles from a diverse panel of experts in evolutionary medicine. These principles should be useful to advance recent recommendations made by The Association of American Medical Colleges and the Howard Hughes Medical Institute to make evolutionary thinking a core competency for pre-medical education. METHODOLOGY: The Delphi method was used to elicit and validate a list of core principles for evolutionary medicine. The study included four surveys administered in sequence to 56 expert panelists. The initial open-ended survey created a list of possible core principles; the three subsequent surveys winnowed the list and assessed the accuracy and importance of each principle. RESULTS: Fourteen core principles elicited at least 80% of the panelists to agree or strongly agree that they were important core principles for evolutionary medicine. These principles over-lapped with concepts discussed in other articles discussing key concepts in evolutionary medicine. CONCLUSIONS AND IMPLICATIONS: This set of core principles will be helpful for researchers and instructors in evolutionary medicine. We recommend that evolutionary medicine instructors use the list of core principles to construct learning goals. Evolutionary medicine is a young field, so this list of core principles will likely change as the field develops further.

Does selection for short sleep duration explain human vulnerability to Alzheimer's disease?

Compared with other primates, humans sleep less and have a much higher prevalence of Alzheimer 's disease (AD) pathology. This article reviews evidence relevant to the hypothesis that natural selection for shorter sleep time in humans has compromised the efficacy of physiological mechanisms that protect against AD during sleep. In particular, the glymphatic system drains interstitial fluid from the brain, removing extra-cellular amyloid beta (eAß) twice as fast during sleep. In addition, melatonin - a peptide hormone that increases markedly during sleep - is an effective antioxidant that inhibits the polymerization of soluble eAß into insoluble amyloid fibrils that are associated with AD. Sleep deprivation increases plaque formation and AD, which itself disrupts sleep, potentially creating a positive feedback cycle. These and other physiological benefits of sleep may be compromised by short sleep durations. Our hypothesis highlights possible long-term side effects of medications that reduce sleep, and may lead to potential new strategies for preventing and treating AD.

The evolutionary significance of depressive symptoms: different adverse situations lead to different depressive symptom patterns.

Although much depression may be dysfunctional, the capacity to experience normal depressive symptoms in response to certain adverse situations appears to have been shaped by natural selection. If this is true, then different kinds of situations may evoke different patterns of depressive symptoms that are well suited to solving the adaptive challenges specific to each situation. The authors called this the situation-symptom congruence hypothesis. They tested this hypothesis by asking 445 participants to identify depressive symptoms that followed a recent adverse situation. Guilt, rumination, fatigue, and pessimism were prominent following failed efforts; crying, sadness, and desire for social support were prominent following social losses. These significant differences were replicated in an experiment in which 113 students were randomly assigned to visualize a major failure or the death of a loved one.

An evolutionary life-history framework for understanding sex differences in human mortality rates.

Sex differences in mortality rates stem from genetic, physiological, behavioral, and social causes that are best understood when integrated in an evolutionary life history framework. This paper investigates the Male-to-Female Mortality Ratio (M:F MR) from external and internal causes and across contexts to illustrate how sex differences shaped by sexual selection interact with the environment to yield a pattern with some consistency, but also with expected variations due to socioeconomic and other factors.