Founded in 1883 by English polymath Francis Galton, the Eugenics movement advocated for the select breeding of only those people who possessed desirable hereditary traits (as determined by the mostly white male European and United States-based Eugenicists). Eugenics sought the “improvement” and “thriving” of humankind.  Individuals deemed genetically “inferior” or “unfit” to reproduce for reasons such as mental or physical disability, LGBTQI+ leanings, representing disfavored races, illness, addiction, and being a criminal, were discouraged from breeding. 
In 1878, just five years before he would become known as the “father of Eugenics,” Galton began layering multiple exposures from glass-mounted photographic negatives of portraits to make composite images comprised of multiple superimposed faces.  These photographs, he later suggested, helped communicate the goals of Eugenics: determining who should and should not produce children. This photographic technique allowed him to give enduring, tangible, visual form to “generic mental images,” or the mental impressions we form about groups of people—perhaps better known as “stereotypes.” He wrote:
A generic mental image may be considered . . . nothing more than a generic portrait stamped on the brain by the cumulative, successive impressions made by its component images. Francis Galton, Generic Images (London: William Clowes and Sons, 1879), p. 166
Galton suggests that the process of making a composite photographic portrait is similar to the process of forming stereotypes, only the impression is “stamped” successively on a light-sensitive surface instead of in the mind.
To illustrate this, Galton added an illustration (see above) to the start of his book Inquiries into Human Faculty and Its Development. In it, he reveals the results of combining profile portraits from six different relief images of Alexander the Great from medals (top row, left); a frontal and side portrait made by combining the photographs of two sisters to tease out their visual likenesses (top row, middle); and a combination portrait made by superimposing the frontal portraits of six family members (top row, right). Rather than provide an accurate likeness of any one of the constituent images’ subjects, Galton’s composites reveal the visual “average appearance” of artists’ portraits of Alexander the Great (which he presumed to be more accurate to his actual likeness than any one artist’s portrait), two sisters, and six family members. Areas of similarity between the portraits grow darker from repeated imprinting on the photographic plate to reveal an imagined, hypothetical person who never lived—but who nonetheless represents a “generic mental image” for of a group of people.
To make these composite portraits and others, Galton carefully aligned the axes of the eyes of each portrait and adjusted the size of each subject’s face for uniformity of scale. He re-photographed multiple images on a single negative, using a technique he pioneered. As Galton articulated in articles published for audiences in the U.S. and Europe, any archive of up to 500 photographs could be combined to make a single group portrait, as long as each image had consistent facial shapes, proportions, and pupil sizes/axes.  The exposure time for each constituent portrait was equal to the total length of the exposure divided by the number of photographs to be included in the composite, so that each included portrait received equal visual presence in the final composite image.
Galton’s technique of composite photography enjoyed credibility as a means for translating stereotypes into tangible pictures that also functioned as data visualizations. Ethnographic photography also communicated stereotypes of people from other races and parts of the world, and became a means by which these people were categorized, stereotyped, and “Othered.”  These photographers’ work circulated within the scientific circles Galton occupied, and were part of the intellectual culture of the Victorian age.
Defining “good” and “bad” breeding in the composite portrait
In addition to forming composite images that articulated family resemblances and amalgamated artists’ pictures of famous historical figures, Galton’s techniques were embraced by the Eugenics movement. Quite literally, “Eugenics” (from the Greek words “good” and “born”) encouraged the reproduction of people with “good” genes (Positive Eugenics), as it discouraged those with “bad” genes from having children (Negative Eugenics). Galton’s photographs gave tangible visual manifestation to both categories.
For example, in Inquiries into Human Faculty and Its Development, Galton defines the appearance of individuals with tuberculosis and consumption. The amalgamated physical appearance of these individuals—with their delicate facial features, gaunt complexions and narrow faces—are contrasted to the adjacent composite of 23 Royal Engineers (British army soldiers), with their strong brow lines, squared jaws, and personifications of vigor. With composite photography, Galton could illustrate the hereditary “strength”—or positive eugenics merits—of some groups (the Royal Engineers, in this case) over others who, he believed, possessed undesirable traits, such as the tendency for illness. He also capitalized on the presumed objectivity of the medium of photography, with the expectation that it provided full-field, unaltered views of objects as they appeared, to enhance the scientific veracity of his visual stereotypes. without regard for the selections he made.
Altering the sample set
Although Galton’s composite-making practice was considered exacting, rigorous, and even “scientific” in its precision and objectivity, the archival images he used were often selected or omitted for technical and aesthetic reasons. A complete set was almost never used. In his 1909 autobiography, Galton explained that he selected constituent images that “were not greatly unlike, and were of the same size, as judged by measuring the vertical distance between the pupils of the eyes and the parting of the lips.” Galton’s tendency to cherry-pick only the ideal images (perhaps those that conveyed his stereotypes of the group) for inclusion subverted the presumed visual objectivity (of visual “proof”) the pictures lent the Eugenics movement.
Galton continued to make composite portraits to validate his stereotypes for other groups, with studies such as The Jewish Type from 1883. It was not until Adolph Hitler and Nazi Germany adopted Eugenics that it began to fall from favor. However, Eugenics has emerged again as a subject for debate as human gene editing and other reproductive technology in the late twentieth and early twenty-first centuries have made selective breeding an open question once again.
Notes: Francis Galton. “Eugenics: Its Definition, Scope, and Aims,” Nature, No. 1804, Vol. 70 (May 26, 1904), p. 82.  Galton, “Eugenics: Its Definition, Scope, and Aims,” p. 82.  Chloe S. Burke and Christopher J. Castaneda, “The Public and Private History of Eugenics: An Introduction,” The Public Historian, Vol. 29, No. 3 (Summer 2007), p. 6.  Francis Galton, “The Making of a Composite Portrait,” Nature, 18 (1878), pp. 97–100.  Ethnographic photography had a precedent in the portraiture of John Thomson, Charles Alfred Woolley, and John Lamprey: Allen Hockley, “John Thomson’s China – I.: Illustrations of China and Its People, Photo Albums (1873–1874) – Chinese ‘Types,’” Visualizing Cultures (2010). Accessed Nov. 29, 2021: https://visualizingculturxes.mit.edu/john_thomson_china_01/ct_essay_04.pdf; Elizabeth Edwards, “Photography and Anthropological Intention in Nineteenth Century Britain,” Revista de Dialectología y Traditiones Populares, Vol. 53, No. 1 (1998). pp. 23–48.  Francis Galton, Memories of My Life (London: Methuen, 1908), p. 269.
Kris Belden-Adams, Eugenics, ‘Aristogenics,’ Photography: Picturing Privilege (New York: Routledge, 2020).
Josh Ellenbogen, Reasoned and Unreasoned Images: The Photography of Bertillon, Galton, and Marey (University Park: The Pennsylvania State University Press, 2012).
Elizabeth Edwards, “Evolving Images: Photography, Race and Popular Darwinism,” in D. Donald and J. Munro, eds. Endless Forms, Darwin, Natural Sciences and the Visual Arts (New Haven/London: Yale University Press, 2009), pp 166–193.
Anne Maxwell, Picture Imperfect: Photography and Eugenics, 1879–1940 (East Sussex, U.K.: Sussex Academic Press, 2008).