Paul William Ewald

Paul William Ewald
University of Louisville | UL · Department of Biology

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113
Publications
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Publications

Publications (113)
Article
Full-text available
We propose a general barrier theory as an evolutionary framework for understanding coevolutionary effects of conflicts of interest in natural and human systems. It is generalized from the barrier theory of cancer, which describes how cancer develops through the evasion of mechanisms that block unregulated cellular reproduction and survival. Barrier...
Article
Full-text available
Individuals who are minoritized as a result of race, sexual identity, gender, or socioeconomic status experience a higher prevalence of many diseases. Understanding the biological processes that cause and maintain these socially driven health inequities is essential for addressing them. The gut microbiome is strongly shaped by host environments and...
Article
Full-text available
The application of evolutionary and ecological principles to cancer prevention and treatment, as well as recognising cancer as a selection force in nature, has gained impetus over the last 50 years. Following the initial theoretical approaches that combined knowledge from interdisciplinary fields, it became clear that using the eco‐evolutionary fra...
Article
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The barrier theory of cancer integrates environmental, genetic, and infectious contributions to oncogenesis into a single framework. The full spectrum of symbiotic influences on oncogenesis, however, still needs to be brought into this framework, particularly for symbionts that are classified as commensals or mutualists. This paper contributes to t...
Article
Full-text available
Inflammation, infection and depression: an evolutionary perspective - Volume 1 - Caroline Doyle, Walker A. Swain, Holly A. Swain Ewald, Paul W. Ewald
Article
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While it is generally known that the risk of several cancers in humans is higher in urban areas compared with rural areas, cancer is often deemed a problem of human societies with modern lifestyles. At the same time, more and more wild animals are affected by urbanization processes and are faced with the need to adapt or acclimate to urban conditio...
Article
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The microbiome is composed of hundreds of interacting species that have co-evolved with the host and alterations in microbiome composition have been associated with health and disease. Insights from evolutionary ecology may aid efforts to ameliorate microbiome-associated diseases. One step toward this goal involves recognition that the idea of comm...
Article
Darwinian medicine applies principles of evolutionary adaptation and natural selection to the study of disease, emphasizing that a full understanding of medical problems requires an understanding of why states of disease exist. There are three evolutionary explanations for the presence of disease: natural selection is insufficiently strong to elimi...
Article
Based on the abundant studies available on humans showing clear associations between rapid environmental changes and the rate of neoplasia, we propose that human activities might increase cancer rate in wild populations through numerous processes. Most of the research on this topic has concentrated on wildlife cancer prevalence in environments that...
Chapter
Infectious agents are accepted causes of many cancers of humans and domesticated animals, but reports of infection-induced cancers in nature are relatively rare. Human pathogens, particularly viruses, are now known to cause cancer by sophisticated mechanisms that compromise barriers to cancer. These mechanisms have evolved convergently in different...
Chapter
While it is widely acknowledged that intratumor heterogeneity is mostly generated by genomic instability, we propose that genomic instability is only part of a proximate mechanism that maintains intratumor heterogeneity through oncogenic selection. Within tissues and organs, malignant cells achieve greater success by cooperating in the process of t...
Article
Cancers have been reported in bone and soft tissue of ancient agricultural populations. Fossilized bones from prehistoric periods provide evidence of tumors but only one example of cancer. Difficulties in diagnosing the causes of lesions in mummified tissue and fossilized bone, and in interpreting the prevalence of cancers from remains, draw attent...
Chapter
Human infectious disease results from many factors (e.g., human behavior, disease organisms, institutions) that often interact as opposing agents in accordance to the investor–exploiter dichotomy. Directing interventions to influence these opposing roles may improve human health by differentially influencing the success of exploiters and investors....
Article
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Background Since the beginning of the twentieth century, infection has emerged as a fundamental aspect of cancer causation with a growing number of pathogens recognized as oncogenic. Meanwhile, oncolytic viruses have also attracted considerable interest as possible agents of tumor destruction.DiscussionLost in the dichotomy between oncogenic and on...
Book
While it is widely acknowledged that intratumor heterogeneity is mostly generated by genomic instability, we propose that genomic instability is only part of a proximate mechanism that maintains intratumor heterogeneity through oncogenic selection. Within tissues and organs, malignant cells achieve greater success by cooperating in the process of t...
Chapter
A balanced approach to the causes of cancer requires assessment of genetic, environmental, and infectious influences and the interactions among them. An evolutionary perspective provides a framework for such assessments because evolutionary selection acts on cells during the process of oncogenesis, on individuals to generate protection against onco...
Article
Similar to parasites, cancer cells depend on their hosts for sustenance, proliferation and reproduction, exploiting the hosts for energy and resources, and thereby impairing their health and fitness. Because of this lifestyle similarity, it is predicted that cancer cells could, like numerous parasitic organisms, evolve the capacity to manipulate th...
Article
Full-text available
This study investigated whether sexually transmitted infections and lifestyle variables are associated with premenstrual syndrome (PMS) as well as particular manifestations commonly associated with PMS. Data were gathered from medical records of 500 regularly cycling women. The following infectious agents were investigated: human papillomavirus, Ch...
Poster
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Exacerbations of chronic diseases that are known or suspected to be caused by infection near the onset of menses suggest that PMS may actually be a collection of manifestations of unidentified chronic infectious diseases.
Article
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Evolutionary considerations suggest that oncogenic infections should be pervasive among animal species. Infection-associated cancers are well documented in humans and domestic animals, less commonly reported in undomesticated captive animals, and rarely documented in nature. In this paper, we review the literature associating infectious agents with...
Article
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The evolutionary perspective of cancer (which origins and dynamics result from evolutionary processes) has gained significant international recognition over the past decade and generated a wave of enthusiasm among researchers. In this context, several authors proposed that insights into evolutionary and adaptation dynamics of cancers can be gained...
Article
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The evolutionary perspective of cancer (which origins and dynamics result from evolutionary processes) has gained significant international recognition over the past decade, and generated a wave of enthusiasm among researchers. In this context, several authors proposed that insights in evolutionary and adaptation dynamics of cancers can be gained b...
Article
Full-text available
For an increasing number of biologists, cancer is viewed as a dynamic system governed by evolutionary and ecological principles. Throughout most of human history, cancer was an uncommon cause of death and it is generally accepted that common components of modern culture, including increased physiological stresses and caloric intake, favor cancer de...
Article
Joint infectious causation of cancer has been accepted in a few well-studied instances, including Burkitt's lymphoma and liver cancer. In general, evidence for the involvement of parasitic agents in oncogenesis has expanded, and recent advances in the application of molecular techniques have revealed specific mechanisms by which host cells are tran...
Article
Purpose of review: To use insights from evolutionary biology to assess the current evidence for the causes, treatment, and prevention of inflammatory bowel disease (IBD). Recent findings: When analyzed in the context of evolutionary adaptation, recent assessments of genetic, microbial, and environmental associations with IBD implicate infectious...
Article
Full-text available
We propose an evolutionary framework, the barrier theory of cancer, which is based on the distinction between barriers to oncogenesis and restraints. Barriers are defined as mechanisms that prevent oncogenesis. Restraints, which are more numerous, inhibit but do not prevent oncogenesis. Processes that compromise barriers are essential causes of can...
Article
An understanding of oncogenesis can be fostered by an integration of mechanistic studies with evolutionary considerations, which help explain why these mechanisms occur. This integration emphasizes infections and mutations as joint essential causes for many cancers. It suggests that infections may play a broader causal role in oncogenesis than has...
Article
The aim of this section is to give brief indications of the character, content, and cost of new books in the various fields of biology. More books are received by The Quarterly than can be reviewed critically. All submitted books, however, are carefully considered for originality, timeliness, and reader interest, and we make every effort to find a...
Article
Full-text available
Assessments of future threats posed by infection have focused largely on zoonotic, acute disease, under the rubric “emerging diseases.” Evolutionary and epidemiological studies indicate, however, that particular aspects of infrastructure, such as protected water supplies, vector-proof housing, and health care facilities, protect against the emergen...
Article
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An evolutionary perspective reveals why immune processes are an intricately interconnected with each other and with other biological processes within multicellular organisms. This web-like interconnectedness has important implications for medical interventions. Evolutionary considerations suggest that direct manipulation of molecules and processes...
Article
Immunological aetiologies of disease are not generally well understood, but have been attributed to intrinsic immunological imbalances, infectious triggers or persistent infections. Evolutionary considerations lead to the formulation of three feasible categories of immunopathology for common diseases. One category of hypotheses presumes that the im...
Chapter
The current integration of evolution with medicine is artificially narrow because it reflects the biases of medicine as a whole and the specializations of particular investigators. If evolutionary principles are to offer a fundamental framework for understanding medical issues they should help identify these biases and the areas over which integrat...
Article
Full-text available
The aim of this section is to give brief indications of the character, content, and cost of new books in the various fields of biology. More books are received by The Quarterly than can be reviewed critically. All submitted books, however, are carefully considered for originality, timeliness, and reader interest, and we make every effort to find a...
Article
For the past half-century, the dominant paradigm of oncogenesis has been mutational changes that disregulate cellular control of proliferation. Parasitic causes of cancer were first incorporated into this paradigm by suggesting mechanisms through which parasitism might increase mutational damage, such as generation of mutagenic compounds during imm...
Article
Premenstrual syndrome is a collection of heterogeneous symptoms that are attributed to hormonal fluctuations and that vary among individuals for unknown reasons. We propose that much of what is labeled "premenstrual syndrome" is part of a broader set of infectious illnesses that are exacerbated by cyclic changes in immunosuppression, which are indu...
Article
An analysis of fitness costs and benefits associated with pathogenicity suggests that modes of transmission are key determinants of evolution toward severely pathogenic, benign, or mutualistic symbioses. Specifically, this approach suggests that symbionts with mobile life history stages should evolve toward extremely severe parasitism, vector-borne...
Article
Recent studies have provided evolutionary explanations for much of the variation in mortality among human infectious diseases. One gap in this knowledge concerns respiratory tract pathogens transmitted from person to person by direct contact or through environmental contamination. The sit-and-wait hypothesis predicts that virulence should be positi...
Chapter
IntroductionVirulence-antigen Vaccines against Bacteria Corynebacterium diphtheriaeBordetella pertussisHemophilus influenzaeVirulence-antigen Vaccines against VirusesCircumventing Social Barriers to VaccinationA Call for Field Experiments Corynebacterium diphtheriaeBordetella pertussisHemophilus influenzae
Article
At the close of the 19th century, the germ theory had generated a new understanding of the causes of acute infectious diseases and revealed new directions for study. This understanding contributed to the greatest improvements in health in the history of medicine. At the end of the 20th century, the second stage of this disciplinary development is o...
Article
Current theory in evolutionary biology indicates that host-parasite relationships may evolve towards equilibrial states of severe disease. Although this view differs from the conventional belief that commensalism is the ideal equilibrium for both host and parasite, the literature on human infectious diseases confirms 2 specific predictions derived...
Article
Literature on schizophrenia and other mental illnesses has emphasized the compatibility of evidence with genetic causation without adequately considering alternative hypotheses of disease causation. Although some studies from the mid-20th century reported associations between certain pathogens and schizophrenia, only recently has the possibility of...
Article
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We used the nuclear polyhedrosis virus of the gypsy moth, Lymantria dispar, to investigate whether the timing of transmission influences the evolution of virulence. In theory, early transmission should favour rapid replication and increase virulence, while late transmission should favour slower replication and reduce virulence. We tested this predi...
Article
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Health promotion's promise is enormous, but its potential is, as yet, unmatched by accomplishment. Life expectancy increases track more closely with economic prosperity and sanitary engineering than with strictly medical advances. Notable achievements in the past century--the decreased incidences of epidemic infections, dental caries, and stomach c...
Article
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Evolutionary considerations implicate infectious causation of atherosclerosis and help to resolve different risk factors as parts of an overall process of disease causation. An evolutionary approach also provides insight for the timing of research efforts to provide better control of pathogen evolution. In particular, evolutionary considerations em...
Article
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Perspectives in Biology and Medicine 43.3 (2000) 406-448 Over the past two centuries, diseases have been separated into three categories: infectious diseases, genetic diseases, and diseases caused by too much or too little of some noninfectious environmental constituent. At the end of the 19th century, the most rapid development was in the first of...
Article
Insights into the evolution of virulence may aid efforts to control or even prevent emerging diseases. Specifically, dangerous pathogens can be distinguished from those that pose relatively little threat by identifying characteristics that favor intense exploitation of hosts by pathogens, hence causing high virulence. Studies to date have implicate...
Article
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Evolutionary theory may contribute to practical solutions for control of disease by identifying interventions that may cause pathogens to evolve to reduced virulence. Theory predicts, for example, that pathogens transmitted by water or arthropod vectors should evolve to relatively high levels of virulence because such pathogens can gain the evoluti...
Article
Insights into the evolution of virulence may aid efforts to control or even prevent emerging diseases. Specifically, dangerous pathogens can be distinguished from those that pose relatively little threat by identifying characteristics that favor intense exploitation of hosts by pathogens, hence causing high virulence. Studies to date have implicate...
Article
Full-text available
Control of emerging infectious diseases will be difficult because of the large number of disease-causing organisms that are emerging or could emerge and the great diversity of geographic areas in which emergence can occur. The modern view of the evolution of pathogen virulence--specifically its focus on the tradeoff between costs and benefits to th...
Article
Full-text available
Nectar guides are common among insect-pollinated plants, yet are thought to be rare or absent among hummingbird-pollinated plants. We hypothesize that the lower lips and trumpet-shaped orifices of many hummingbird flowers act as nectar guides to direct hummingbirds to the flowers' nectar and orient the birds for pollination. To test this hypothesis...
Article
Full-text available
Flexible pedicels are characteristic of birdpollinated plants, yet have received little attention in studies of hummingbird-flower interactions. A major implication of flexible pedicels is that flowers may move during pollination. We examined whether such motion affected interactions between ruby-throated hummingbirds (Archilochus colubris) and jew...
Article
Guidelines for submitting commentsPolicy: Comments that contribute to the discussion of the article will be posted within approximately three business days. We do not accept anonymous comments. Please include your email address; the address will not be displayed in the posted comment. Cell Press Editors will screen the comments to ensure that they...
Article
High mutation rates are generally considered to be detrimental to the fitness of multicellular organisms because mutations untune finely tuned biological machinery. However, high mutation rates may be favoured by a need to evade an immune system that has been strongly stimulated to recognize those variants that reproduced earlier during the infecti...
Article
High mutation rates are generally considered to be detrimental to the fitness of multicellular organisms because mutations untune finely tuned biological machinery. However, high mutation rates may be favoured by a need to evade an immune system that has been strongly stimulated to recognize those variants that reproduced earlier during the infecti...
Article
Full-text available
Theoretical considerations implicate food availability and intrusion pressure as important determinants of territory size, but empirical studies have led to contradictory conclusions about cause-and-effect relationships among these three variables. To investigate this problem, we provided patches of electronically controlled artificial flowers, whi...
Article
At the close of the 19th century, the germ theory had generated a new understanding of the causes of acute infectious diseases and revealed new directions for study. This understanding contributed to the greatest improvements in health in the history of medicine. At the end of the 20th century, the second stage of this disciplinary development is o...
Article
Playback of territorial song of Anna's hummingbirds near newly available feeders attracted intruders to the feeders and hastened territory establishment. The first feeding by intruders was not significantly earlier in the presence of playback, apparently because intruders were tentative about feeding in the presence of playback. Playback of song on...
Article
Experimental reductions of productivity on feeding territories of Anna's hummingbirds (Calypte anna) decreased intrusion rate. This trend contrasts with the absence of strong correlations between intrusion rate and productivity in previous experimental studies. Consideration of sample sizes, productivity rates, and time-dependent influences on intr...
Article
Full-text available
Diarrhoeal diseases are primary contributors to millions of deaths annually. Yet, little is known about the evolutionary reasons for the differences in virulence among gastrointestinal pathogens. Applying the comparative, cost/benefit approach of evolutionary biology this paper proposes that waterborne transmission should favour evolution towards h...
Article
Full-text available
Application of evolutionary principles to epidemiological problems indicates that cultural characteristics influence the evolution of parasite virulence by influencing the success of disease transmission from immobilized, infected hosts. This hypothesis is supported by positive correlations between virulence and transmission by biological vectors,...
Article
Per os inoculations of migratory grasshoppers Melanoplus sanguinipes with the microsporidian protozoan Nosema acridophagus resulted in an increase in the grasshoppers' preferred temperature by about 6 C. Maintenance of grasshoppers at febrile and nonfebrile temperatures showed that fever benefited infected grasshoppers in terms of survival and grow...
Article
Full-text available
Changes in territorial behavior of blackchinned hummingbirds ( Archilochus alexandri ) in response to experimental changes in territory quality were investigated using artificial feeders and simultaneous, pair-wise observations of owners. Some of the responses of A. alexandri were similar to those documented by a previous study of the Anna's hummin...
Article
According to current theory, dominance relationships may depend on asymmetries between adversaries in their expected net gain from contested resources. A prediction derived from this theory was confirmed in the field by experimentally creating asymmetries between neighbouring territorial hummingbirds with regard to their net energy gains from their...
Article
Full-text available
To test whether alterations in aggressive behavior are responses to short-term resource depression, use of inexpensive and escalated territorial defense by Anna hummingbirds was analyzed as a function of the degree to which food could be depressed by foraging activities of territory owners and intruders. On depressible territories use of gorget dis...
Article
(1) Abundance of a protein-rich food was experimentally increased in territories of red-winged blackbirds during the 1977 and 1978 breeding seasons in Washington state, U.S.A. (2) Supplemental feeding advanced the onset of nesting. The effect was increased when food was provided earlier in the prebreeding season. Within experimental territories the...

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