Paul W. Ewald (born 1953) is an

evolutionary biologist Evolutionary biology is the subfield of biology that studies the evolutionary processes (natural selection, common descent, speciation) that produced the diversity of life on Earth. It is also defined as the study of the history of life for ...

, specializing in the

evolutionary ecology Evolutionary ecology lies at the intersection of ecology and evolutionary biology. It approaches the study of ecology in a way that explicitly considers the evolutionary histories of species and the interactions between them. Conversely, it can ...

parasitism Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted structurally to this way of lif ...

evolutionary medicine Evolutionary medicine or Darwinian medicine is the application of modern evolutionary theory to understanding health and disease. Modern biomedical research and practice have focused on the molecular and physiological mechanisms underlying heal ...

agonistic behavior Agonistic behaviour is any social behaviour related to fighting. The term has broader meaning than aggressive behaviour because it includes threats, displays, retreats, placation, and conciliation. The term "agonistic behaviour" was first implemen ...

, and

pollination Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds ...

biology. He is the author of '' Evolution of Infectious Disease'' (1994) and ''Plague Time: The New Germ Theory of Disease'' (2002), and is currently director of the program in Evolutionary Medicine at the Biology Department of the University of Louisville. Ewald is known for his "theory of virulence”, suggesting that "the deadlier the germ, the less likely it is to spread", and his theory that many common diseases of unknown origin are likely the result of chronic low-level

infections An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmiss ...

from

viruses A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's 1 ...

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

protozoa Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...

Education and career

Ewald received his BSc in 1975 from the

University of California, Irvine The University of California, Irvine (UCI or UC Irvine) is a public land-grant research university in Irvine, California. One of the ten campuses of the University of California system, UCI offers 87 undergraduate degrees and 129 graduate and pr ...

, in biological sciences and his PhD in 1980 from the

University of Washington The University of Washington (UW, simply Washington, or informally U-Dub) is a public research university in Seattle, Washington. Founded in 1861, Washington is one of the oldest universities on the West Coast; it was established in Seattle a ...

, in

zoology Zoology ()The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the Animal, animal kingdom, including the anatomy, structure, embryology, evolution, Biological clas ...

, with specialization in

ecology Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overlaps wi ...

and

evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...

. He was formerly a professor of biology at

Amherst College Amherst College ( ) is a private liberal arts college in Amherst, Massachusetts. Founded in 1821 as an attempt to relocate Williams College by its then-president Zephaniah Swift Moore, Amherst is the third oldest institution of higher educatio ...

, and is currently director of the program in evolutionary medicine in the Biology Department of the

University of Louisville The University of Louisville (UofL) is a public research university in Louisville, Kentucky. It is part of the Kentucky state university system. When founded in 1798, it was the first city-owned public university in the United States and one of ...

Ideas

Ewald asserts, along with a growing body of studies, that many common diseases of unknown origin are likely the result of chronic low-level

from

. For example,

cervical cancer Cervical cancer is a cancer arising from the cervix. It is due to the abnormal growth of cells that have the ability to invade or spread to other parts of the body. Early on, typically no symptoms are seen. Later symptoms may include abnormal ...

can be caused by the

human papilloma virus Human papillomavirus infection (HPV infection) is caused by a DNA virus from the ''Papillomaviridae'' family. Many HPV infections cause no symptoms and 90% resolve spontaneously within two years. In some cases, an HPV infection persists and res ...

, some cases of liver cancer are caused by

hepatitis Hepatitis is inflammation of the liver tissue. Some people or animals with hepatitis have no symptoms, whereas others develop yellow discoloration of the skin and whites of the eyes (jaundice), poor appetite, vomiting, tiredness, abdominal pa ...

C or B and the bacteria ''

Helicobacter pylori ''Helicobacter pylori'', previously known as ''Campylobacter pylori'', is a gram-negative, microaerophilic, spiral (helical) bacterium usually found in the stomach. Its helical shape (from which the genus name, helicobacter, derives) is though ...

'' has been proven to cause

stomach ulcers Peptic ulcer disease (PUD) is a break in the inner lining of the stomach, the first part of the small intestine, or sometimes the lower esophagus. An ulcer in the stomach is called a gastric ulcer, while one in the first part of the intestines ...

. Ewald argues that many common diseases of currently unknown etiology, such as cancers, heart attacks, stroke and Alzheimer's, may likewise be also caused by chronic low-level microbial infection. Ewald disagrees with the popular theory that

genes In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

alone dictate chronic disease susceptibility. Ewald, whose background is in

evolutionary biology Evolutionary biology is the subfield of biology that studies the evolutionary processes (natural selection, common descent, speciation) that produced the diversity of life on Earth. It is also defined as the study of the history of life fo ...

, points out that any disease causing gene that reduces survival and reproduction would normally eliminate itself over a number of generations. Ewald says that "''chronic diseases, if they are common and damaging, must be powerful eliminators of any genetic instruction that may cause them''." One example of this is

schizophrenia Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social withdra ...

; patients with this mental illness rarely reproduce. Ewald argues that, just by evolutionary pressures, schizophrenia would have already been eliminated if its causes were strictly genetic; he suggests that in the future, an infectious cause of schizophrenia will be discovered. Ewald explains that purely genetic causes of chronic disease will persist only if a genetic instruction provides a compensating benefit (for example, the disease

sickle cell anemia Sickle cell disease (SCD) is a group of blood disorders typically inherited from a person's parents. The most common type is known as sickle cell anaemia. It results in an abnormality in the oxygen-carrying protein haemoglobin found in red blo ...

is caused by a genetic mutation that, in

heterozygote Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism. Mo ...

s, protects against malaria, which kills millions worldwide each year). Further evidence for a non-genetic etiology of diseases like schizophrenia, Ewald also points out, comes from

concordance Concordance may refer to: * Agreement (linguistics), a form of cross-reference between different parts of a sentence or phrase * Bible concordance, an alphabetical listing of terms in the Bible * Concordant coastline, in geology, where beds, or la ...

studies on

identical twins Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of TwinLast Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two em ...

, which measure the percentage of identical twins who both develop a disease. A concordance of 100% indicates a primarily genetic disease, which is not really influenced by environmental factors like infection, nutrition, or toxins. Huntington's disease, for example, has a concordance rate of 100%, indicating a predominately genetic etiology. However, when the concordance rate is lower, this indicates environmental factors like infectious microbes or toxin exposure are playing a causal role. Schizophrenia's concordance is approximately 35-60%, suggesting, says Ewald, that microbes are etiologically involved. Another example is

breast cancer Breast cancer is cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, milk rejection, fluid coming from the nipple, a newly inverted nipple, or a re ...

: Ewald notes that in the case of

, when one twin develops

, the other twin has only a 10% to 20% chance of developing the disease, and this concordance rate of just 20% again indicates that environmental factors like infectious microbes or toxins are likely playing large causal roles in breast cancer. Ewald's curiosity regarding the

evolutionary Evolution is change in the heredity, heritable Phenotypic trait, characteristics of biological populations over successive generations. These characteristics are the Gene expression, expressions of genes, which are passed on from parent to ...

process of infections was sparked by a bad case of diarrhea he had in 1977. His first thought during this bout was that his body was using diarrhea to expel the

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

and he should avoid anti-diarrheal medication. Looking at the problem from the standpoint of the organism, expulsion was not an

benefit. The only benefit to the pathogen causing the sickness would be the potential transmission to other hosts; much like the particulate expelled during coughing, diarrhea can be a means of distribution. Another major influence on Ewald's thinking in evolutionary biology terms was the

HIV The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immune ...

virus, which once caught, initially remains inactive for years thus allowing it to spread, before the chronic disease of

AIDS Human immunodeficiency virus infection and acquired immunodeficiency syndrome (HIV/AIDS) is a spectrum of conditions caused by infection with the human immunodeficiency virus (HIV), a retrovirus. Following initial infection an individual m ...

finally manifests, incapacitates, and eventually kills the host.

Awards

In 2010, ''

Utne Reader ''Utne Reader'' (also known as ''Utne'') ( ) is a digital digest that collects and reprints articles on politics, culture, and the environment, generally from alternative media sources including journals, newsletters, weeklies, zines, music, and ...

'' magazine named Ewald as one of the "25 Visionaries Who Are Changing Your World" for his research on the link between infections and cancers.

Quotes

* "Like many great ideas in biology, the idea implicating infectious causation in chronic diseases, though simple, has far-reaching implications. It is so simple and so significant, that one would think it would have been recognized by many and would be the starting point for any discussion on the causes of disease. Not yet." — Paul W. Ewald. * "If I were going to put my money on it, I would bet that by 2050—hopefully earlier—we’ll have found that more than 80 percent of all human cancer is caused by infection." — Paul W. Ewald. * Of Ewald's theory: "It opens our eyes to many quite weird possibilities about disease that most medical scientists, tending to be unaware of current evolutionary thought, don't think of." — evolutionary biologist

William D. Hamilton William Donald Hamilton (1 August 1936 – 7 March 2000) was a British evolutionary biologist, recognised as one of the most significant evolutionary theorists of the 20th century. Hamilton became known for his Theoretical biology, theoretic ...

Publications

Books * '' Evolution of Infectious Disease'' (1994)
''Plague Time: The New Germ Theory of Disease''
(2002) Articles
"Transmission modes and the evolution of virulence"
(1991) * "The Evolution of Virulence: A Unifying Link between Parasitology and Ecology" (1995)
"Guarding Against the MostDangerous Emerging Pathogens: Insights from Evolutionary Biology"
(1996) * "Vaccines as evolutionary tools: The virulence-antigen strategy" (1996) in ''Concepts in Vaccine Development'' * "Alternative Transmission Modes and the Evolution of Virulence" (2002) in ''Adaptive Dynamics of Infectious Diseases'' * "Virulence Management in Humans" (2002) in ''Adaptive Dynamics of Infectious Diseases''
Other publications by Paul Ewald on PubMed

References

External links

Toward a unified, evolutionary theory of cancer
presentation by Paul Ewald 2016
Interview With Evolutionary Biologist Paul Ewald
by Amy Proal
The Big Idea That Might Beat Cancer and Cut Health-Care Costs by 80 Percent
by Andrew Grant, Discover Magazine, Sept 2009

by Judith Hooper, The Atlantic Monthly, Feb 1999

Can we domesticate germs? (TED2007)

The Infection Connection
by Harriet Washington, Psychology Today
List of Human Diseases Linked to Infectious Pathogens
{{DEFAULTSORT:Ewald, Paul W 1950s births Living people Evolutionary biologists University of Washington College of Arts and Sciences alumni University of California, Irvine alumni University of Louisville alumni