Evolutionary Epidemiology: an Art Gallery

Anonymous, 1330. Anjou Legendarium. Vatican Library, Vatican City.

In the final scene of the Legend of Saint Ladislaus, the King rests in the arms of the girl he has just saved from a Cuman warrior. The girl "looks into the head" of the King.

Jan van Eyck: The Arnolfini Marriage (The Marriage of Giovanni Arnolfini and Giovanna Cenami) 1434. Oil on wood, 81.8 * 59.7 cm; National Gallery, London

Why do we reproduce sexually? Being males and females, or men and women, most living organisms reproduce sexually. Thus, we can produce only half as many offspring as the yield of an asexual population consisting of females only. Apparently, sexuality emerged and became the dominant way of reproduction in the living world due to the selection pressure exerted by pathogens. The offspring produced sexually are more resistant against infections than the offspring produced non-sexually. However, pathogens utilise our sexuality to enhance their own transmission, and they also reproduce themselves sexually so as to produce offspring more resistant against the attacks of our immune systems.

Albrecht Dürer: Four Horsemen of Apocalypse, 1498. Woodcut, 39 * 28 cm

Through human history, war always coincided with epidemics.

Aztec smallpox victims. Bernardino de Sahagún: Historia De Las Cosas de Nueva Espana, Volume 4, Book 12.

In 1519, Hernando Cortez landed in Mexico. Together with his 4-600 men, and the smallpox they carried accidentally, he destroyed the powerful Aztec Empire within two years. When he arrived, about 25-30 million natives inhabited the region. Half a century later, 3 million native people survived.

Pieter Bruegel: The Triumph of Death, 1562. Oil on panel, 117 * 162 cm; Museo del Prado, Madrid

The view of Europe during a medieval plague epidemic. Yersinia pestis bacteria normally occur in rodents but fleas may occasionally transmit them into human populations where they can establish self-sustainable epidemics. The disease originates from Central and East Asia and first appeared in Europe in 1346 among the tatar forces sieging the town of Caffa in the Crimea. The tartars used catapults to hurl human plague cadavers into the town, from where the defenders fled by ships toward the Mediterranian. The first European plague epidemic emerged in Southern Europe in the next year and eradicated 30% of the European population soon.

Jan Vermeer: The Milkmaid, 1658-60. Oil on canvas, 18 * 16 in. Rijksmuseum, Amsterdam

Humans domesticated the wild ox (Bos taurus) to ensure a safe access to the milk of cows, thus, accidentally, also opened a way to the bacteria of tuberculosis (Mycobacterium tuberculosis) to invade humans. Once one of the most important human diseases, tuberculosis is now greatly decimated by "pasteurisation" and the widespread use antibiotics. Not forever, unfortunately. New, drug-resistant strains are spreading globally and especially in the former Soviet Union. Prisoners, refugees, homeless people and AIDS-patients are at particular risk.

Gerard ter Borch: The Family of the Stone Grinder, 1653-55, Oil on canvas, Staatliche Museen, Berlin

For the wast majority of humankind, lousyness was (is) not a horryfying infestation but the nurmal way of life. Head lice was (is) more widespread among children, wny body lice was widespread among adults as well.

Jan Vermeer van Delft: Girl with a Pearl Earring. circa 1665. Oil on canvas, 44,5 * 39 cm, Mauritshuis, Hága, Hollandia

Animals exhibit sevaral adaptions to identify, to encapsulate and to kill any non-self materilas – and pathogens in particular – entering into their bodies. The immune system of vertabrates is particularly complex. However, animals with much simpler body structures and shorter lifes tend to apply simple defenses. Mulluscs, such as bivalves, clams, oysters or mussels, simply develop a hard calcium carbonate layer to encapsulate any non-self material entering their bodies. 

Anton Einsle: Portrait of Ferenc Kölcsey. Hungarian Academy of Sciences, Budapest.

Typically, there is a negative trade-off between virulence and transmission capability of pathogens; thus the most virulent pathogens tend to transmit poorly. The smallpox virus, however, was an exception; it was highly contagious while it could permanently cause a mortality rate of about 30% in the European population. Survivors often became blind due to infection. The last infected human was a Somalian peasant in 1973, but stocks of the smallpox virus are still maintained for military purposes.

Eugéne Delacroix: Medea is about to kill her children, 1838. Oil and canvas, Louvre, Paris.

According to Greek mythology, Medea killed her children when her husband left her. Can natural selection favour such extreme acts of spite? Some of us believe that Hamiltonian spite, i.e. harming conspecifics without a direct benefit, does exist in Nature. Some animals actively infest conspecifics by the pathogens reproducing in themselves.

Alfred Rethel: First outbreak of the cholera in Paris during a masquerade, 1851.

Cholera became known and respected probably since medieval urbanisation. It is transmitted by drinking water, causes dysentery and thus a potentially lethal dehydration of the human body. The disease has not got a chronic form, but the pathogenic Vibrio cholerae bacteria may live, feed and multiply themselves in aquatic reservoirs such as in Chironomid egg masses. Cholera outbreaks still cause epidemics with high human mortality in developing countries.

John Tenniel: Alice and the Red Queen running hand in hand, 1871. Illustration for L. Carroll: Through the Looking Glass and What Alice Found There. Wood-engraving

"...they were running hand in hand, and the Queen went so fast that it was all she could do to keep up with her...The most curious part of the thing was, that the trees and the other things around them never seemed to changed their places at all..." According to Carroll's tale, the Red Queen is a chess-piece who has to run continuously to keep her position in a running world. Is the co-evolution of hosts and parasites a similar run to achieve a constant position in a world running around us?

Arnold Boecklin: The Plague. 1898. Tempera on wood, 149 *105 cm, Kunstmuseum Basel, Basle.

Plague often inspired human imagination. The soviet Biopreparat started to produce freeze–dried plague bacteria from the early 1970s. This company employed  6.500 scientists and 25.000 workers who were — officially — producing vaccines for peaceful purposes only. A military excersice to test these products on the remote "Rebirth" island of lake Aral killed about 500.000 saiga antelopes on the nearby Turgay steppe in 1988. Then the so-called "super-plague" was already weaponised for large-scale military use. This was a genetically modified version of Yersinia pestis having an increased virulence and being resistant against antibiotics. After repeated unveilings President Yelcin prohibited offensive bio-weapon developments.

Robert Thom: Semmelweis — Defender of Motherhood. 1966.

Neither doctors, nor medicines, but hand-washing spares most human lives from contagious diseases. In the 19th century, mortality of healthy women was about 18% in the delivery room of the Vienna City Hospital, Austria. This was reduced to about 3% by introducing obligatory hand-washing for the medical personnel by Dr. Semmelweis, a Hungarian medical doctor. He was forced to leave because he made a bad reputation for the Hospital by his 'ridiculous and groundless' claim that the puerperal sepsis was caused by unvisible little creatures transmitted by the hands of the medical personnel. Soon he died due to a contagious disease, a disease of the same kind he was fighting against.

Underwood & Underwood: U.S. inspectors examining eyes of immigrants looking for signs of trachoma. 1913. b&w film copy negative, Ellis Island, New York Harbor.

Immigrants, unlike the local majority, tend to transmit pathogens to genetically non-related individuals. Evolutionary theory predicts that under such circumstances, organisms can benefit from enhancing pathogen transmission to conspecifics. Consequently, when behaving instinctively, immigrants are predicted to transmit pathogens more readily than the so-called ethnic majority. On the other hand, when behaving instinctively, the majority is predicted to show counter-adaptations, such as xenophobia to exclude immigrants from the context of social relations. When behaving instinctively, they are predicted to blame immigrants for transmitting pathogens either ignorantly or purposely, even without any cause for such denouncing accusations. The immigration law of 1891 made it mandatory that all immigrants coming into the United States be given a health inspection. At Ellis Island, however, only those who traveled in third class had to pass through the inspection.

The execution of Margaretha Geertruida Zelle alias Mata Hari.

Press photo, authenticity debated. Casernes de Vincennes, 1917.

Well hidden in our usual body structure, pathogens and parasites pretend to be normal components of our bodies. Meanwhile, they profitise on monopolising the nutrients and other resources of our bodies, and manipulate our behaviours in their own interest. And they also risk to face the most severe punishment if identified as non-selfs by our immune systems. Like spies uncovered.

Edvard Munch: After Spanish Flu, self portrait, 1919.

Spanish flu was an influenza pandemic caused by an unusually deadly variant of Influenza A subtype H1N1. It killed about 50 (estimates: 20-100) million people between 1918-1920.  It soon went extinct globally, however, nowadays it is possible to synthesized it de novo.

RKO Radio Pictures: King Kong "The Eighth Wonder of the World", 1933. 100 mins, 35 mm black and white negative, USA. (Originally titled: The Beast, King Ape, and Kong)

According to this movie, inhabitants of the remote Skull Island sacrificed a young virgin to the monster called Kong each year, in order to safe themselves from greater losses. Does it worth for animals to sacrifice a limited amount of space and nutrients to parasites so as to ensure that no more harm will be caused? Studies on reptiles that develop specific "mite-sacs" to hide and feed their blood-sucking Trombiculid mites appear to support this view. 

Perpetual Peacock Painting, 19 * 28", by Loretta Casler, wc, wc pencil, gouache.

William Hamilton and Marlene Zuk hypothesized that female birds' preference for males with particularly large and bright secondary sexual characters improves the genetic quality of their offspring. Brighter males have had fewer parasites while developing their plumage, because they harbour better resistance alleles than their duller rivals. Testosterone, the hormone regulating the development of these sexual signals, is immune-suppressive. Thus males who try to cheat by developing plumages sexier than they can afford will fall due to infections. Indeed, chicks fathered by brigther peacocks exhibit a lower level of mortality.