Brain Pickings

Trees of Life: A Visual History of Scientific Diagrams Explaining Evolution

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Mapping 450 years of humanity’s curiosity about the living world and the relationships between organisms.

Since the dawn of recorded history, humanity has been turning to the visual realm as a sensemaking tool for the world and our place in it, mapping and visualizing everything from the body to the brain to the universe to information itself. Trees of Life: A Visual History of Evolution (public library) catalogs 230 tree-like branching diagrams, culled from 450 years of mankind’s visual curiosity about the living world and our quest to understand the complex ecosystem we share with other organisms, from bacteria to birds, microbes to mammals.

Though the use of a tree as a metaphor for understanding the relationships between organisms is often attributed to Darwin, who articulated it in his Origin of Species by Means of Natural Selection in 1859, the concept, most recently appropriated in mapping systems and knowledge networks, is actually much older, predating the theory of evolution itself. The collection is thus at once a visual record of the evolution of science and of its opposite — the earliest examples, dating as far back as the sixteenth century, portray the mythic order in which God created Earth, and the diagrams’ development over the centuries is as much a progression of science as it is of culture, society, and paradigm.

Theodore W. Pietsch writes in the introduction:

The tree as an iconographic metaphor is perhaps the most universally widespread of all great cultural symbols. Trees appear and reappear throughout human history to illustrate nearly every aspect of life. The structural complexity of a tree — its roots, trunk, bifurcating branches, and leaves — has served as an ideal symbol throughout the ages to visualize and map hierarchies of knowledge and ideas.

The Ladder of Ascent and Descent of the Intellect, not tree-like at first glance, but certainly branching dichotomously, the steps labeled from bottom to top, with representative figures on the right and upper left: Lapis (stone), Flamma (fire), Planta (plant), Brutum (beast), Homo (human), Caelum (sky), Angelus (angel), and Deus (God), a scheme that shows how one might ascend from inferior to superior beings and vice versa. After Ramon Lull (1232–1315), Liber de ascensu et descensu intellectus, written about 1305 but not published until 1512.

The 'Crust of the Earth as Related to Zoology,' presenting, at one glance, the 'distribution of the principle types of animals, and the order of their successive appearance in the layers of the earth’s crust,' published by Louis Agassiz and Augustus Addison Gould as the frontispiece of their 1848 Principles of Zoölogy. The diagram is like a wheel with numerous radiating spokes, each spoke representing a group of animals, superimposed over a series of concentric rings of time, from pre-Silurian to the 'modern age.' According to a divine plan, different groups of animals appear within the various 'spokes' of the wheel and then, in some cases, go extinct. Humans enter only in the outermost layer, at the very top of the diagram, shown as the crowning achievement of all Creation.

'Genealogy of the class of fishes' published by Louis Agassiz in his Recherches sur les poissons fossiles (Research on fossil fishes) of 1844.

The 'genealogico-geographical affinities' of plant families based on the natural orders of Carl Linnaeus (1751), published by Paul Dietrich Giseke in 1792. Each family is represented by a numbered circle (roman numerals), the diameter of which gives a rough measure of the relative number of included genera (arabic numerals).

The unique egg-shaped 'system of animals' published by German zoologist Georg August Goldfuss in his Über de Entwicklungsstufen des Thieres (On animal development) of 1817.

'Universal system of nature,' from Paul Horaninow’s Primae lineae systematis naturae (Primary system of nature) of 1834, an ingenious and seemingly indecipherable clockwise spiral that places animals in the center of the vortex, arranged in a series of concentric circles, surrounded in turn by additional nested circles that contain the plants, nonmetallic minerals, and finally metals within the outermost circle. Not surprisingly, everything is subjugated to humans (Homo) located in the center.

Ernst Haeckel’s famous 'great oak,' a family tree of animals, from the first edition of his 1874 Anthropogenie oder Entwickelungsgeschichte des menschen (The evolution of man).

(More on Haeckel’s striking biological art here.)

Tree by John Henry Schaffner showing the relationships of the flowering plants. The early split at the base of the tree leads to the monocotyledonous plants on the left and the dicotyledons on the right.

Schaffner, 1934, Quarterly Review of Biology, 9(2):150, fig. 2; courtesy of Perry Cartwright and the University of Chicago Press.

A phylogeny of horses showing their geological distribution throughout the Tertiary, by Ruben Arthur Stirton.

Stirton, 1940, plate following page 198; courtesy of Rebecca Wells and the University of California Press.

Ruben Arthur Stirton’s revised view of horse phylogeny.

Stirton, 1959, Time, Life, and Man: The Fossil Record, p. 466, fig. 250; courtesy of Sheik Safdar and John Wiley & Sons, Inc. Used with permission.

William King Gregory’s 1946 tree of rodent relationships.

Gregory, 1951, Evolution Emerging: A Survey of Changing Patterns from Primeval Life to Man, vol. 2, p. 757; fig. 20.33; courtesy of Mary DeJong, Mai Qaraman, and the American Museum of Natural History.

The frontispiece of William King Gregory’s two-volume Evolution Emerging.

Gregory, 1951, Evolution Emerging: A Survey of Changing Patterns from Primeval Life to Man, vol. 2, p. 757; fig. 20.33; courtesy of Mary DeJong, Mai Qaraman, and the American Museum of Natural History.

Images courtesy of Johns Hopkins University Press

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