We are happy to announce that Diagrams 2022 will host the following workshops as its associated events. The workshops will take place on September 13 2022

Diagrams of Life and Evolution

organised by Nathalie Gontier

Online (Password: AppEEL) & Onsite in Rome, Italy

Workshop description
The evolution of life today is commonly illustrated by diagrams that include timelines, phylogenetic trees, and networks. Each of these diagrams more or less associate with different evolution schools that aim at depicting different aspects of the evolutionary process. Timelines associate with older natural history research that began to situate the evolution of life in deep time, phylogenetic trees were mostly developed within Neodarwinian schools to illustrate the descent with modification of species, and network models primarily associate with research on interactions that occur during development (e.g. gene regulatory networks) and ecology (e.g. food networks, host-microbiome relationships) or interactions that underlie reticulate evolution (evolution that occurs by means of lateral gene transfer, symbiosis, symbiogenesis, hybridization or infective heredity). These evolutionary diagrams, moreover, find their intellectual precursors in cosmographies that include scales of nature or chains of being, life cycles or wheels of time, genealogies and pedigrees.

This workshop will investigate these major diagrams of evolution, their precursors in intellectual history, and their adequacy in depicting the mechanisms and processes or general aspects of life that they intent to illustrate. Along the way, the workshop furthermore aims to expose curious parallels between diagrammatic research in the life and the natural sciences, reasons for which might be found in the way humans conceptualize diagrams cognitively. This workshop is therefore also relevant for participants in the psychological tract.

Cycles of Life – Chains of Being – Scales of Nature – Pedigrees and Genealogies – Trees of life – Evolutionary Timelines – Phylogenetic trees – Networks – Mode and Tempo of Evolution – Hierarchy theory

Call for Participation
In this workshop, we call for abstracts that provide historical, philosophical, psychological, or educational analyses of diagrams that either depict the evolution of life or that precede these diagrams in intellectual history. Diagrams can include:

  • Evolutionary timelines, phylogenetic trees, networks
  • Scales of nature, chains of being, religious and mythological trees of life
  • Pedigrees and genealogies (including Jesse and Adamic trees)
  • Wheels of time, cycles of life and death, coming and becoming, generation and decay

Topics of discussion can include, but are not limited to the following research questions:

  • What are the cultural precursors of evolutionary diagrams?
  • What, if any, is the historical relation between older cosmographies and evolutionary diagrams?
  • How does the intellectual history of diagrams of life and evolution correlate with advances in mathematics?
  • What are the historical parallels with diagram formation in the biological and the natural sciences?
  • How able are evolutionary diagrams in depicting the theories, mechanisms, processes, phenomena they intent to illustrate?
  • How able are evolutionary diagrams in depicting the mode and/or tempo in evolution?
  • What are the major differences between timelines, trees, and networks?
  • How are evolutionary hierarchies depicted in diagrams?
  • How is evolutionary causation depicted in diagrams?
  • How do evolutionary diagrams depict time and space?
  • How do evolutionary diagrams underlie model-based reasoning?
  • How do evolutionary diagrams facilitate scientific or public understanding of evolution?
  • Do evolutionary diagrams drive evolutionary thinking?
  • Diagrams as educational tools

A selection of submissions will be considered for publication in the Springer Nature book series Interdisciplinary Evolution Research.

Instructions on how to submit you Abstract
Interested scholars can send their abstracts (max. 500 words) together with title, author name/s, affiliation/s, and contact details directly to Nathalie Gontier. Be sure to mention Diagrams2022 in the email subject. The deadline for abstract submissions is June 15th, 2022. Notification will follow by June 30th.

Important Notice
Note that accepted participants will have to register as regular participants of the main conference.

Cordial thanks to our sponsers!


08:30 – 10:30: Session I: Theory & Contextualization

Nathalie Gontier – Welcome and Introduction to Diagram of Life and Evolution

Applied Evolutionary Epistemology Lab, Centro de Filosofia das Ciências, Departamento de História e Filosofia das Ciências, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal

The evolution of life today is commonly illustrated by diagrams that include timelines, phylogenetic trees, and networks. Each of these diagrams more or less associate with different evolution schools that aim at depicting different aspects of the evolutionary process. Timelines associate with older natural history research that began to situate the evolution of life in deep time, phylogenetic trees were mostly developed within Neodarwinian schools to illustrate the descent with modification of species, and network models primarily associate with research on interactions that occur during development (e.g. gene regulatory networks) and ecology (e.g. food networks, host-microbiome relationships) or interactions that underlie reticulate evolution (evolution that occurs by means of lateral gene transfer, symbiosis, symbiogenesis, hybridization or infective heredity). These evolutionary diagrams, moreover, find their intellectual precursors in cosmographies that include scales of nature or chains of being, life cycles or wheels of time, genealogies and pedigrees.

Paloma López Grüninger – Between the Lines: The Visual Language of Evolutionary Diagrams and its Consequences for Interpretation

Institute Digital Communication Environments, University of Applied Sciences, Northwestern Switzerland & Academy of Art and Design, Basel, Switzerland

Diagrams are curious mixtures of concept and materiality. When translating abstract thoughts into the visual domain, they are forced to grow a body: relations between concepts translate into lines, similarities into spatial interrelations, hierarchies into colors and shapes. Their conceptual origin seems to free them from any ambiguity: meaning is codified by visual parameters, and there is a correct way to interpret them. When discussing diagrams, we expect them to support visually – and ideally even to communicate unequivocally – the theoretical ideas they represent. Reading between the lines of their visual expression is unacceptable: no personal interpretation is intended at any moment. But is it possible for us, as highly visual beings that we are, to read structures and shapes without relating them to our visual experience of the world that surrounds us? Even the most simple line always displays certain expressive characteristics – is it a vector-drawn, precise, homogeneous, and “objective” line? Or does its visual shape tell through its haptic features the hesitations of its author, those moments in which the ink flow falters while the mind questions the lines drawn by the hand, telling, therefore, a subjective story of an individual and its thoughts? The idea that we interpret emotionally the designed elements that surround us grew much attention in the last decades. Emotional Design is, as such, not a new concept, as design has always considered the visual characteristics of its elements to decide appearance: from the choice of a typeface for a specific company to the color palette for an ad to the typology of an illustration. But it is now, in the context of capitalistic growth, where it developed into a much-celebrated concept, as the awareness awoke that not only function but also emotional connection can decide which of the many variants of a product will finally prove successful on the market. Yet this awareness of the emotional dimensions of the visual seems to circumvent the discussion about diagrams. In my presentation I want to show how evolutionary diagrams and their precursors present an exciting domain to investigate how the interpretation of visual language and their emotional aspects intermingles with coded meaning. From the early images, where metaphorical interpretations were explicitly intended by connecting the structural aspects of diagrams with figurative depictions (for example, Ramon Lull’s Ladder of Ascent and Descent of the Intellect in 1305 to the Phylogenetic Trees from Ernst Haeckel in the mid-nineteenth century) to current visualizations of trees and networks, where metaphorical associations happen only through their visual expression: the communicative power of all those images exceeds by far their strictly coded meaning.


Raphaël Sandoz – Mapping Science with Diagrams: From Trees to Networks

Department of History and Philosophy of Science, University of Geneva, Switzerland

Throughout history, many taxonomic systems have been put forward to map and organize human knowledge into a coherent whole. Various schematic devices, such as trees, tables, circles, networks, and many other, have been used to visually illustrate the order and coordination of the different fields of research. For instance, Jeremy Bentham developed an “encyclopedic tree” of the sciences, Antoine-Augustin Cournot a “synoptic table of human knowledge”, while Charles Edward Hooper opted for circular diagrams to that end. In order to explore methodically the evolution of such data structures over time, I have built a historical atlas ( collecting more than 250 maps of knowledge designed by as many scholars throughout the centuries, including an iconographic database. By confronting the diagrams with the discourses of scholars about the organization of science, I will examine how the former have influenced the latter. I will pay particular attention to the logical constraints attached to each type of diagrams, and show that the theoretical debates on knowledge organization have often been guided—sometimes unconsciously—by the graphical requirements of a symmetry or an empty cell to be filled.

Marilyn Mitchell – Motivations Underlying the Representation of Time in Family and Evolutionary Tree Diagrams

Faculty of Society & Design, Bond University, Gold Coast, Australia

This research discusses the representation of time within family and evolutionary tree diagrams to consider that the design of time is a fundamental choice in all diagrams, one that is motivated by a variety of needs. The discussion begins with a general model of the visual representation of time or tense which is developed from linguistics. It then considers the development of tree diagrams in the West from the earliest available copies in the eighth century to the present with examples coming from the domains of history, genealogy, religion, anthropology, genetics, evolution, and popular culture. Each example is discussed first in relation to its use and then by its composition using the visual variables of time’s direction, the primary reference point, scale, symbols, positions of symbols, and the size, color, tone and texture of any symbols and graphical elements. Overall, the choice for time’s direction of flow in a tree diagram depends upon how the diagram will be used, how much information needs to fit onto the page or screen, a culture’s patterns for writing and reading, aesthetics, linguistic metaphors, values, and the “ideal-real” continuum along the vertical dimension.

Mitchell, M. (2014). Fitting issues: The visual representation of time in family tree diagrams. Sign Systems Studies, 42(2/3), 241-280, and

Mitchell, M. (2016). More to reading images: Motivations underlying horizontal and vertical time-related graphics. The International Journal of Literacies, 23(4).

11:00 – 13:00: Session II: Timelines, Pre- and Post-Evolutionary Trees

Graham Shields – The Geological Timescale

Department of Earth Sciences, University College London, United Kingdom

Prehistoric miners around the world invented stratigraphy by tracing ore deposits beneath the ground. Early geologists, for example Giovanni Arduino in the mid-eighteenth century, first used the principle of superposition to divide rocks (and time) into Primary and Secondary, followed eventually by Tertiary and Quaternary. Belated acceptance that Secondary rocks contain a predictable sequence of distinctive fossil assemblages eventually permitted global stratigraphic correlation, which could then be used to reconstruct biological evolution. Following thorny disputes, these global rock packages or systems became synonymous with the well-known geological periods (Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic and Cretaceous, which all precede Lyell’s Tertiary). Around the mid-nineteenth century, it became evident that mass extinctions had occurred, leading to the amalgamation of periods into eras (Palaeozoic, Mesozoic and Cenozoic), which together make up the Phanerozoic Eon, or the time of visible life (from the Greek phaneros). Further division of Systems (Periods) led to Stages (Ages) and Series (Epochs) subdivisions. The difficulty in applying the same biostratigraphic approach to older rocks led to the introduction of simplistic, rounded ages for pre-Cambrian time about thirty years ago. However, biostratigraphy is not the only game in town these days. Not only can rocks be dated more precisely using radioactive clocks, but both geochemistry and geophysics are used increasingly to correlate strata. The pre-Cambrian fossil record is also continually improving. Several recent attempts have been made to introduce rock-based subdivision for all Earth history, taking into account such global events as the Snowball Earth glaciations, hence the Cryogenian Period (after Cryos for icy cold). Here I will outline one recent attempt to do this amid renewed recognition that all era-level subdivisions have a tectonic subtext for even mass extinctions coincide with volcanic eruptions and related climate change. Most pre-Cambrian period names are based on Greek words, carrying on traditions established in the nineteenth century for eons and eras, but adapting them to describe geological and environmental phenomena of global import. Because every region of the world has its own local stratigraphic nomenclature, agreeing an international time chart is a huge undertaking involving many countries, geological surveys and countless working lives. The internationally agreed time scale facilitates communication across borders, for example by standardizing geological maps, and acts as a key pedagogical tool, merging multiple evolutionary concepts of Earth history. Key to this process is continual reassessment of the validity of subdivisions, which can be revised following suggestions by panels of experts, and ratification by the International Union of Geological Sciences (IUGS). Our understanding of Earth history has come a long way since the first attempts at stratigraphic correlation, and it is incumbent on us to translate emerging knowledge into its most intuitive and informative form for future generations.

Shields, G.A. and 34 co-authors (2022) A template for an improved rock-based subdivision of the pre-Cryogenian timescale. Journal of the Geological Society, v. 179, jgs2020-2022.

Petter Hellström – Form, Not Function: A Revisionist History of Early Systematic Trees

Department of History of Science and Ideas, Uppsala University, Sweden

In recent years, there has been a proliferation of studies charting the history of tree diagrams in natural history and systematics. Whereas some of these studies have focused on one or a few arboreal schemes, others have presented long histories, often spanning centuries. Yet, in spite of the apparent ambition of placing the present into perspective, there is a persistent tendency of telling the story backwards. Not only are tree diagrams from the late eighteenth and early nineteenth centuries frequently styled as the ‘pre-evolutionary’ or ‘pre-Darwinian’, or even as the ‘roots’ of later, phylogenetic trees, but it is also common to project our present expectations on tree diagrams onto the past. Not least is it common to explain the appearance of tree diagrams in natural classification by recourse to emergent evolutionism. The history of early systematic trees is, however, a question of form, not function. In the late eighteenth and early nineteenth centuries, when arboreal and genealogical diagrams were first employed to organise natural kinds and imagine natural order, there existed no given relationship between the tree as a format of diagrammatic representation, and the evolutionary meanings we have come to associate with trees since the second half of the nineteenth century. Together with André Gilles and Marc Philippe, I have previously argued that one of the most frequently cited early tree diagrams in natural classification, Augustin Augier’s ‘Botanical Tree’ (1801), cannot in any reasonable way be made to play the role of a proto-evolutionary forerunner to phylogenetic trees, announcing the rise of time or generation as a factor in natural classification (Hellström, André, and Philippe, 2017a, 2017b; Hellström, 2019). In this paper, I push the argument further by proposing a revisionist account of early systematic trees beyond theindividual example. Drawing on a number of diagrams from the late eighteenth and early nineteenth centuries, while attending to the functions they performed in the eyes of their authors and contemporaries, I argue that trees were attractive to contemporary scholars not because they presented a radically different vision of natural order, but rather because of their convenient, branching shape, which harmonised well with established ideas and practices, and because they could be made to perform a number of functions previously associated with other diagrammatic formats, including keys, ladders, and maps.

Hellström, Petter, Gilles André, and Marc Philippe (2017a). ‘Life and Works of Augustin Augier de Favas (1758–1825), Author of “Arbre Botanique”’. Archives of Natural History 44, no. 1: 43–62.

Hellström, Petter, Gilles André, and Marc Philippe (2017b). ‘Augustin Augier’s Botanical Tree. Transcripts and Translations of Two Unknown Sources’. Huntia 16, no. 1: 17–38.

Hellström, Petter (2019). Trees of Knowledge. Science and the Shape of Genealogy. Uppsala: Acta Universitatis Upsaliensis.

Erica Torrens & Ana Barahona – Darwin’s trees: Metaphors of Biological Order

Estudios Sociales de la Ciencia, Departamento de Biología Evolutiva, Facultad de Ciencias, Universidad Nacional Autónoma de México, México

Few other scientific theories have become so much a part of western culture as the theory of evolution. The evolutionary theory by natural selection is the dominant idea in science and central to today’s biological thinking and environmental concerns. At the heart of these ideas lies the notion of the ‘tree of life.’ It is commonplace to assume that this idea derives from Charles Darwin himself. In my talk I will explain that history tells us otherwise. To be sure, one of the most fundamental concepts of Darwin’s argument in 1859 was that species share a common origin from a single ancestor and have subsequently diverged through time. In the fourth chapter of his book, On the Origin of Species, Darwin included a picture that he used as evidence for this notion. His diagram is an abstract and irregular design, not a tree in a literal sense, and not described by Darwin as such. In his subsequent books, Darwin never included any other depictions of this kind. Why is it, then, that popular accounts of evolution always use the image of a ‘tree’? In this conference I will first trace the history of ideas about trees in animal and plant classification from very early times and also look carefully at ‘trees’ in other fields such as human genealogy and linguistics. This sets the scene for a fresh look at Darwin’s contributions to this visual imagery (we will explore Darwin’s tree pictures chronologically, and how they furthered his own researches). Then, I will continue the tree story after Darwin, moving from late Victorian popular culture right up to the twenty-first century, presenting several new interpretations and a wealth of fascinating visual material drawn from scientific and popular texts and old displays in natural history museums. In short, this talk will take the audience on a fabulous visual journey through the extraordinary imagery that has explained evolutionary theory to many thousands of readers and museum visitors for more than 100 years.

Bárbara Jiménez Pazos – In Search for Darwin’s Conception of Time in The Origin of Species: A semantic Journey Through Diagrams, Trees, Scales, and Cycles

Facultad de Educación, Filosofía y Antropología, San Sebastián & Facultad de Relaciones Laborales y Trabajo Social, Vitoria, Spain

Darwin is one of the pillars of evolutionary thought, and time is one of the conceptual gears of the Theory of Evolution without which the concept of evolution would not make sense in cardinal branches of knowledge of Darwinian evolutionism such as geology. Geological and biological evolution are mutually reinforcing: fossils cannot be dated and interpreted satisfactorily without the history of the Earth; in turn, a good knowledge of the evolution of species allows us to better date the strata of the Earth and, consequently, to better reconstruct its geological evolution in time. The connection point between geological evolution and the evolution of species is, therefore, the concept of time, a necessary element for bio-geological change in nature. Defining Darwin’s conception of time becomes, consequently, a crucial task to establish a more solid conceptual basis of evolutionary thought in the history of science. How did Darwin represent and describe time in his major work The Origin of Species? An in-depth semantic analysis of language describing visual representations of evolution over time, such as Darwin’s phylogenetic diagram, and key time-related concepts and metaphors, such as “chain”, “scale”, “tree (of life)”, “cycle”, “line”, “progress”, “succession” and, of course, “time”, will reveal onto-epistemological presuppositions underlying the Darwinian conception of time. A computer-assisted analysis focused especially on the frequency, deletion or addition of these terms throughout the six editions of the Origin, which Darwin corrected over the years, will answer questions such as whether Darwin’s conception of time varied or remained static over time, whether Darwin has played a crucial role in bringing forth concepts about time that underlie evolutionary thinking, or whether he maintained the concepts inherited from predecessors such as Thomas Burnet, James Hutton and Charles Lyell.

14:00 – 15:30 Session III: Impact of Ordering Systems

Murray Leaf – What Kinship Terminologies Are and How We Know It

School of Economic, Political, and Policy Sciences, University of Texas at Dallas, USA

Kinship is a fundamental feature and basis of human societies. We know this even though we do not have a clear understanding of what it is. The reason is intuitive and comparative. All societies have something we can see as comparable to whatever we recognize as kinship in our own, although never exactly the same. It is also true, but less widely recognized, that all societies also have other kinds of relationships beyond kinship. But few, if any, of these other kinds of relations are clearly universal. Some have government; some arguably do not even though every community in the world is now at least nominally within some national jurisdiction. Some have hunting organizations; some do not. Some have age-grades; some do not. Some have business firms, some have caste, some have courts, and so on. The fact that there are multiple kinds of organizations presents the problem of distinguishing one from another. This involves language, in the sense that all organizations have named and defined values, roles, and relations. Distinct organizations have roles and relations with distinct names and descriptions; related organizations have roles and relations with related roles and descriptions. Kinship organizations are no exception. Kinship, as a sphere of organization and activity, is distinguished from other spheres by distinct terms for kinship roles and relations, and as a matter of fact—plain fact—at the center of this terminology, or language, is a distinct set or system of terms for the basic relationships that define kinship as such. All kinship systems are marked by a kinship terminology. There is a great deal of confusion over what a kinship terminology is, and how we know it. The confusion is largely generated by an underlying referential conception of meaning deriving from sociological and logical positivism. The alternative I will demonstrate here is pragmatic. Referential theories are set up in terms of words and their referents. Pragmatic theories are set up in terms of ideas and their uses.

Sander Gliboff – Diagrams in Historical Context: The Changing Meaning of Ernst Haeckel’s Human Family Tree

Department of History and Philosophy of Science and Medicine, Indiana University, USA

Diagrams do not always speak for themselves, but can also take on meanings that depend on the associated text, historical context, or readers’ expectations. A most extreme example of such reinterpretation is the diagram of the tree of human evolution, by Ernst Haeckel (1834–1919) from his 1874 book, Anthropogenie. Haeckel was the most influential evolutionary biologist of the 19th century, as both a popularizer and a leader in the project of using comparative embryology and recapitulation theory to reconstruct evolutionary relationships. In the 20th century, however, his reputation declined precipitously, as a younger generation of morphologists sought to make the embryo the creative and driving force of evolutionary change, rather than just a passive recorder of phylogenetic change. Beginning in the 1920s and 1930s Walter Garstang and Gavin de Beer developed a view, revived and politicized by Stephen J. Gould in 1977, of Haeckel as methodologically naïve and taking a rigidly deterministic and linear view of evolutionary progress, including a hierarchy of human races with Europeans at the top. Accordingly, what stands out today for viewers of Haeckel’s diagram is the mighty tree trunk and the linear succession of direct ancestors that rise with it to the human heights. But Haeckel himself had produced numerous other diagrams showing richly branching trees of different animal groups, and the accompanying texts stressed the unpredictability, beauty, and continual creativity and progress of evolution. With that context in mind, one can more easily appreciate that his human tree does indeed have branches, even if Haeckel left little room at the sides of the page for them to flourish, ramify, and progress. One might also be moved to take a closer look at the tiny branches at the top. Do they depict the relatively recent diversification of the races? What becomes of the tree trunk once it reaches the human level? Is there a main line of progress anymore? A new and historically more authentic interpretation of Haeckel’s human tree and of Haeckel’s general picture of evolutionary change is offered.

Kees van Putten – The Decline and Fall of Spatiality in Images of the Order of Nature: Multi-Dimensional Images of the Natural System in the First Half of the 20th Century

Kees van Putten, Center for the History of Philosophy and Science, Faculty of Philosophy, Theology and Religious Studies, Radboud University, The Netherlands

Naturalists used to be of the opinion that there is a coherence between all species in nature, determined by morphological relations between them. They called this comprehensive whole the ‘order of nature’ or ‘natural system’ and dubbed the morphological relations ‘affinities.’ One of the chief goals of pictorial illustrations of the order of nature was to chart and represent these affinities. It is hence no surprise that changes in the definition and understanding of affinities led to a change in the form and dimensionality of the images. As long as the order of nature was visualized as a one-dimensional, ascending ladder, each species was supposed to have a relation of affinity with precisely one species above and one below it. When Linnaeus stated that “All plants show affinities on all sides, like a territory on a geographical map”, he suggested that a two-dimensional image was needed to represent the natural order. When Darwin, in turn, reinterpreted affinity as a “morphological similarity or difference as a result of prior evolutionary development”, the branching course of evolution made it necessary to depict it with genealogical trees. But anyone who tries to express evolutionary deviation by distancing correctly three or more branches ramifying from the same place in an evolutionary tree, will discover that a three-dimensional construct is the result and that a two-dimensional image of it has to be understood as a projection on paper. In the last decades of the nineteenth century such three-dimensional evolutionary trees were published indeed. (Van Putten. 2021. Three‐Dimensional Phylogeny in Two Dimensions, Journal of the History of Biology 54, pp. 639–687) .In the course of the twentieth century, phylogenetic trees and cladograms lost all spatiality and became mere diagrams. Before this happened, however, two renowned botanists published multi-dimensional images of a dazzling complexity. In this lecture I intend to analyze these so-far neglected images. The Dutch biologist Hendrik Jan Lam (1892-1977) strove to create in his images a synthesis of taxonomy, phylogeny and bio-geography, placed under the common denominator of time. (Lam. 1935. Phylogeny of single features, The Gardens’ Bulletin, 9, 1) Lam was influenced by the Japanese botanist Bunzo Hayata (1874-1934), whose images were even more dazzling. Hayata’s twenty years’ experience in systematic botany led him to deny the principle of natural selection of species and to develop his “Dynamic System.” Hayata painted inextricable clusters of species, represented as colorful chains of genes “extended in a boundless three-dimensional space.” (Hayata. 1921. An Interpretation of Goethes Blatt in his “Metamorphose der Pflanzen.” Icones Plantarum Formosarum. X: 75-95 (Taihoku)). Lam would later demonstrate that this space was in fact multi-dimensional. Looking at Lam’s and Hayata’s images while realizing that they are in reality projections on paper of multi-dimensional figures is a historical sensation that deserves to be examined closely in this lecture and later in an article.

Douglas E. Soltis – The Tree of Life Concept through Human History

Laboratory of Molecular Systematics & Evolutionary Genetics, Florida Museum of Natural History; & Department of Biology, University of Florida, USA

Well before Darwin, the Tree of Life concept played a crucial role in human cultures. Trees have been a fundamentally important symbol, with diverse meanings throughout human history. Some scholars have argued that trees and their structure have provided an organizing principle in many aspects of human life, ranging from systems of law to science and religion. Trees have long served as a metaphor for the connectivity of all life, including our own species. Cultures throughout human history have viewed trees as a symbol representing the connection between different levels of existence—the heavens via the crown and the underworld via the roots, with the connectivity of leaves and branches representing the connectivity of all life. The Tree of Life metaphor is one with a long, diverse, and rich history. Most cultures have had a Tree of Life story or myth deeply embedded in their culture; many such myths have striking similarities across very different peoples living in very distant parts of the world. Sometimes that myth involved a mystical tree or tree image, and in others there was a religious or ceremonial connection to actual tree species. Some Tree of Life concepts held by ancient cultures maintained that eating the fruit of the Tree of Life would result in eternal life (e.g., the Christian Bible story). In many cultures the Tree of Life was considered to be growing at the center of the world. This all-important Tree of Life was protected by the supernatural. In these cultures, our own species was believed to be descended from this Tree of Life or just one leaf equal to all other leaves (organisms) on the Tree. Furthermore, destruction of the Tree of Life would result in the end of our species. The Hopi from the southwestern United States have stories about a past world in which its inhabitants exploited nature, to an extent that led to their own destruction. An important metaphor today for the critical need to protect the Tree of Life.

16:30 – 18:00 Session IV: Networks, Webs, and Cycles

Pamela S. Soltis – Networks As Models of Evolutionary History

Biodiversity Institute & Laboratory of Molecular Systematics and Evolutionary Genetics, Florida Museum of Natural History, USA

Ever since Darwin, biologists have portrayed evolutionary history as a tree, the ‘Great Tree of Life.’ Indeed, the predominant model of evolutionary connections among species is a bifurcating tree, just as Darwin depicted in the single figure in On the Origin of Species. Despite challenges to this paradigm, it has persisted for nearly two hundred years and was even strengthened by the rise of explicit methodologies for reconstructing phylogeny in the mid- to late twentieth century. Perhaps ironically, it was application of these approaches, especially to bacteria and plants, that demonstrated complex webs of relationships rather than clean, dichotomously branching trees, thus revealing evolutionary history as a network. Conflict between trees and the presumed taxonomic placement of species and between trees derived from different genes has clearly highlighted the complexity of evolution. In this talk, I will explore the emerging role of the network paradigm, from bacterial origins to its current applications in deciphering, interpreting, and visualizing evolution in plants.

Christos Ouzounis – Bioinformatics, Networks, and LGT

School of Informatics, Quality Assurance of educational, research activities and services and infrastructure & Centre for Research and Technology Hellas, Aristotle University of Thessaloniki, Greece

The first complete genome sequences appeared more than a quarter of a century ago, revealing hidden aspects for the structure and function of cellular organisms (1). Less than a decade later, there was sufficient information to start investigating genomic relationships on a large scale, with hundreds of species whose genomes had been deciphered (2). There were two main results emerging from those studies: first, genome sequences reflected -or indeed amplified- the notion of the three domains of life and their main branches; second, horizontal gene transfer (HGT) was recognized as a force shaping gene content, maybe to an extent less than usually pronounced in the literature. Yet, methods for whole-genome comparison were needed and subsequently developed (3). Taking into account HGT, one of our key findings has been that gene loss is the main factor influencing gene content, followed by vertical inheritance and then horizontal transfer, to the simple formulation of a 3:2:1 ratio — at least for non-eukaryotic genomes (4). Ever since representative genomes of the three domains of life were sequenced, we have proposed the notion of LUCA for the first time, a term that was quickly embraced by the wider community (5). With methods that compare genomes (3) and detect HGT by quantifying the elements that shape gene content (6), we have shown that LUCA was a complex cellular entity with around 1000 genes, as reflected by hundreds of genome sequences then available (7). The quantified depiction of estimated gene content through gene flows was named ‘the Net of Life’ and represents our currently limited understanding of how genomes have evolved for the last three billion years on Earth (8). These conceptual advances provide a detailed framework with which further investigations can be performed regarding unique subtleties of genome biology on a grand scale, and thousands of genome sequences organized into pangenomes at various taxonomic levels (9).

(1) PD Karp, CA Ouzounis, SM Paley (1996) HinCyc: a knowledge base of the complete genome andmetabolic pathways of H. influenzae. ISMB 4, 116-124.

(2) P Janssen, B Audit, I Cases, et al. (2003) Beyond 100 genomes. Genome Biol 4 (5), 1-3.

(3) V Kunin, D Ahren, L Goldovsky, P Janssen, CA Ouzounis (2005) Measuring genome conservation across taxa: divided strains and united kingdoms. Nucl Acids Res 33 (2), 616-621.

(4) V Kunin, CA Ouzounis (2003) The balance of driving forces during genome evolution in prokaryotes. Genome Res 13 (7), 1589-1594.

(5) N Kyrpides, R Overbeek, C Ouzounis (1999) Universal protein families and the functional content of the last universal common ancestor. J Mol Evol 49 (4), 413-423.

(6) V Kunin, CA Ouzounis (2003) GeneTRACE – reconstruction of gene content of ancestral species. Bioinformatics 19 (11), 1412-1416.

(7) CA Ouzounis, V Kunin, N Darzentas, L Goldovsky (2006) A minimal estimate for the gene content of the last universal common ancestor – exobiology from a terrestrial perspective. Res Microbiol 157 (1), 57-68.

(8) V Kunin, L Goldovsky, N Darzentas, CA Ouzounis (2005) The net of life: reconstructing the microbial phylogenetic network. Genome Res 15 (7), 954-959.

(9) A Chasapi et al., (2022) manuscript in preparation.

Frank N. Egerton – Ecology’s Atypical Diagrams

History Department, University of Wisconsin – Parkside, USA

The field of ecology illustrates major data and results of research through a number of diagrams. This talk focusses on two such diagrams, food chains that depict consumer relationships between different species, and isothermal maps that assist depictions of the geographical distribution of plants and animals. Food chains and food webs reach back to 1718, when English naturalist, Richard Bradley, commented: “Insects which prey upon others are not without some others of lesser Rank to feed upon them likewise, and so to infinity. Johnathan Swift turned this into poetry: “So, Nat’ralists observe, a Flea Hath smaller Fleas that on him prey, And these have smaller yet to bite ‘em, And so proceed ad infinitum.” In 1938, zoologist Robert Hegner entitled a book, Big Fleas Have Little Fleas, or Who’s Who Among the Protozoa. Zoologist Alfred Elliott then decorated his 1957 textbook, Zoology, with a whimsical illustration of Hegner’s book title. Carl Linnaeus, in a 1749 essay, “The Economy of Nature,” itemized 2 food chains, one terrestrial, one aquatic. His 2 verbal observations were turned into diagrams by Victor Shelford in 1913. Food chains enter modern ecology through the works of Charles Elton, Warder Allee, and Harvey Epperson. Isothermal maps stem from the collaboration between biology, ecology, and geology. Isothermal maps depict global temperatures and assist in depictions of the geographical distribution of plants and animals. Some of the earliest examples of such diagrams and their use come from Alexander von Humboldt, Charles Lyell, Charles Darwin, and James Dana who used such diagrams in particular to describe the growth of coral reefs. Applications also exist in plant and animal geography. The talk will focus on diagrams introduced by Hewett Watson, Stepan Makaroff, Victor Shelford, James Needham, George Gause, Ralph Bird, amongst others.