by Bonnie DeVarco and Eileen Clegg
The tree is
history’s most enduring symbol, one that demonstrates beautifully how our
visual representations are shaped by human perception. We use shapes to visualize knowledge.
These visualizations, in turn, shape the way we perceive the world. Using the Shape of Thought Approach [1], we can see how history and the leading edge meet in
a universal image that has transformed as humanity has transformed.
Traveling through history in a short series of images and visualizations of the tree, we can see a very different story about human perception than that told in the text-based, historical record. Looking at how humans have used the tree structure as a communication tool, we can see how humanity’s perception of who we are and how we fit in the Universe changed through the centuries.
The following
three tree stories - The Tree of Life, The Tree of Human Relationships and The
Tree of Knowledge - demonstrate how our perception of ourselves and our
relationships is not static.
Instead, it is a dynamic, ever-changing visual conversation between
generations
The
Tree of Life to the Superorganism
The World Tree
The tree is one
of the oldest, most enduring visual metaphors in human history. Because of its
dense networks of roots, branches and foliage, the tree is often used to
visualize relationships between species, languages, families and social groups.
For at least the past 2000 years, it has also been used to map hierarchies of
knowledge and ideas.
The tree is
central to the way many cultures understand the cosmos. It also represents the
source of life. Every sacred practice and religion used tree myths to tell
origin stories, from the oral tradition of the Icelandic Edda to the Tree of
Life in the Judeo Christian Bible. The tree also holds answers to future-oriented questions
about information management, because its growth pattern involves fundamental
properties of geometry, including the Golden Mean, which can be applied as a
design approach or used in algorithms for digital design.
Ancient cultures
throughout the world used the tree as a symbol to represent the construction of
the universe. The oldest symbolic use of the tree was the “World Tree” or the
“Tree of Life.” Mircea Eliade, renowned historian of myth, religion, ritual and
symbol, traced the World Tree idea to the navel of the Earth, a symbol found in
the folklore, stories, rituals and architectures of numerous indigenous
cultures around the world. The Tree of Life is also referred to as “axis mundi”
or the cosmic axis - literally the point of connection between the sky and
earth.
In Norse
mythology the world tree is called “Yggdrasil”, an oak tree that connects all
nine worlds of Norse Mythology together.
Visualized as a colossal tree, the Yggdrasil connected the heavens to
the Earth with its roots extending deep underground.
For pre-Columbian
cultures of Mesoamerica (the Aztec, Izapan, Mixtec Maya and Olmec) the World
Tree was central to the origin of the Cosmos. Their reverence for the Milky Way
was linked directly to the World Tree, the center of the Earth-Sky.
Since ancient
times, we have represented humanity and the gods or higher powers as part of
the tree of life. More than three
millennia ago in Mesopotamia, the tree of life was depicted on bas-reliefs as
both a symbolic and literal image capturing the force that connects all life.
To the ancient
Egyptians, the “tree of life” was an Acacia tree from which the first couple,
Isis and Osiris emerged; they called it the “tree in which life and death are
enclosed." [2] In the Judeo-Christian Bible, the book of Genesis introduces two trees—the Tree
of Life and the Tree of Knowledge of Good and Evil. The fruit from the tree of
life gives immortality. When Adam and Eve eat from the Tree of Knowledge of
Good and Evil, they lose their innocence and are banished from the Garden of
Eden. A more abstract Tree of Life can be found in the Hebrew Kabbalah. Called
the “Sephirot” it is a mystical diagram with ten sephirot (spheres or
emanations). Between the 10 spheres are 22 sacred pathways used to “map”
creation—wisdom from the direct understanding of the nature of God.
The Tree of Life
in the religious or symbolic context encapsulated the idea that everything is
related, from the cosmos to the tiniest atoms in our bodies. In the nineteenth
century we witnessed the emergence of a different tree metaphor, the scientific
tree of life.
Classifying Life
Charles Darwin,
a naturalist who spent a decades carefully charting the variations among
animals of the same species in different environments, helped ground the
fledgling field of evolutionary biology in a more exacting science. He
published his remarkable scientific work, On the Origin of Species in 1859. This book contained only one illustration -
an abstract diagram showing Darwin’s theoretical “tree” of multiple species
related to a common genus.
Many years
earlier Darwin had drawn the genesis of his tree of life idea as a simple
network structure. A sketch next to his earliest thoughts on this tree of
relationships and speciation was drawn 22 years before his legendary book was
finally published.
This sketch is considered to be the very first “network
diagram” - his first depiction of a scientific “tree of life” next to his now
famous words, “I think.”
In the 19th
century, biologist and physician Ernst Haeckel, a protégé of Darwin’s, was the
first to describe and codify the “phylogenetic tree” into five branches. Charles
Darwin knew it was important to visualize the relationships among groups of
organisms for his theory of evolution. Integrating Darwin’s idea of an abstract
branching diagram with Haeckel’s own ideas about genetic evolution, Haeckel animated this vision using a literal
tree structure as a natural metaphor and as a structural diagram of
relationships. Forty years after Darwin’s
sketch, Haeckel published the first official image of the genetic “Tree of
Life”. At the time, the notion of human progress was deeply embedded into the
theory of evolution and humans were considered the pinnacle of the Tree.
As both artist and scientist, Haeckel is best known for his beautiful illustrations of the morphology of microscopic life forms. He named thousands of new species and coined many terms for biology including “phylogeny”. His tree was called the “phylogenetic tree.”
The evolving
morphology of the scientific “tree of life” through the next couple centuries
tells a story about our increasing knowledge of life. In the 20th
and 21st centuries, biologists have acquired a greater understanding
of the genetic relationships among the species. Haeckel’s literal image of the tree with roots still limited
our way to diagram genetic relationships. The Tree of Life was not a direct or
hierarchical lineage, but rather a radial branching of various species from a
common ancestor. By 1960, the
Phylogenetic Tree image organized the species’ into five different “Kingdoms.”
Throughout most of the 20th
century, the tree of life still had five kingdoms; we still shaped our understanding
of life into an anthropomorphic framework by the use of the word, “kingdoms.”
More
recently, the work of scientist Carl Woese started a revolution in the way we
classify life by taking out the hierarchy where humans represent the pinnacle
of evolution. He did this by organizing the tree of life into only three
domains.
At this point,
the plant and animal “kingdoms” were seen to be part of the Eucarya family, and
the name “kingdoms” had been changed to “domains.” The new tree of life’s three
domains were dominated by microscopic life - bacteria and archaea. Lynn
Margulis, who championed a new way of looking at evolution in the theory of
symbiogenesis, originally proposed by cell biologist Boris Kozo-Polyansky
created the first dendrogram showing these trees in the 1970s.
With Haeckel’s
19th century conception of dominant branches of life being animalia,
protista and plantae we look back
to see this as a time when
scientists considered humans and meso-scale life to be the dominant life form
on the planet. Today, we
understand a vastly different story about life on Earth. Humans have been
knocked off their pedestal.
Mapping Life on Earth
Last century, the
burgeoning of genetic knowledge and a concern about the many threats to
biodiversity gave rise to a project to map all life on Earth. Using the power
of the World Wide Web to link the work of hundreds of biologists from around
the world together, the “Tree of Life web project” (ToL) was launched in 2002. In its first five years, this project has networked together the collective
work of professional scientists, teachers, students and amateurs. Over 1.7
million species are identified and searchable on more than 10 thousand web pages. [3]
In 2006, a new,
interactive genomic tree of life was completed by the European Molecular
Biology Laboratory (EMBL) showed us a different picture of the relationship of
humans to other forms of life. It is considered the most accurate tree of life
to date.
The evolution of
tree imagery demonstrates how, through a new generation of science centered
around genomics, we are reframing the way we look at our place on our planet.
New research by Princeton biologist Bonnie Bassler demonstrates that,
genomically speaking, 99 percent of our bodies are comprised of bacteria that
actually talk to each other using a chemical language called quorum sensing.
With new views based on the burgeoning field of genomics we are forced to
further to rethink our place in the tree. Humans have become a “footnote in the
story of bacteria” and life looks more like a vast “superorganism” from this
genomic point of view.


These new visualizations of the tree of life convey a far more accurate "whole systems" view of life on Earth. We see the dominant branches of the tree the very modest place humans, and all mesoscale life hold in a living system dominated by microscale life. As scientists map more and more of the diversity of life, we need bigger, and more dynamic “tree” maps to contain the hundreds of thousands of life forms on the tree. In the late 1990's, CAIDA's WALRUS, a large graph mapping too, enabled us to visualize the structure of the Phylogenetic tree as we know it today through a 3D hyperbolic space through a computer screen.
Even today, 3D
visualization gives us a glimpse of what might be possible when we are able to
fly in and around a 3 dimensional virtual or augmented genomic tree and to
“feel” where we fit into the whole.
We see in the biological Tree of Life, the progression from a linear,
hierarchical vision of relationships to a circular, radial and eventually
spherical image of the tree. As we’ll see below, the metamorphosis of the
family tree paralleled the evolution of the Tree of Life as humans began to
think less traditionally and linearly in our use of metaphors.
A Metaphor becomes an Algorithm
The tree in
nature as a visual metaphor and symbol has become more and more abstract when
we use its image as a structural principle to organize social relationships and
knowledge. But can the tree as a
visual metaphor drawn directly from nature somehow also lead us directly back
to nature’s own geometry? Could we decipher a “code” that would allow us to
automatically generate virtual 3-dimensional trees as realistic as those in the
real world? Although most people are unaware, we are already well on our way to doing that. It is part the most recent history of our visual languages: the history of visual math (fractals) and the emergence of virtual worlds.
In the 1970s biologist and botanist, Aristide Lindenmeyer created a formal grammar – a computer language to model the growth processes of plant development in order to study plant growth. His language is called “L-Systems” and it has been used since that time to generate lifelike branching structures. [4]
Amazingly, the
tree takes us right back to our very special symmetry. When Lindenmeyer began
his work, mathematicians had already discovered two things: (1) math could be
used to understand complex systems that are self generative and these could be
visualized as geometric objects or “fractals” and (2) The Fibonacci series [5] has the special property of “fivefold symmetry” that is an important property
of organic forms of life. Lindenmeyer applied the Fibonacci series to fractal
algorithms in order to create this new “language.” L-systems could generate and
model the morphology of branching organisms that look and act like real
trees. Certainly he, as those
before him understood and used a type of geometric “code” derived from Nature.
The Fibonacci series approximates the Golden Mean.
Today L-Systems
are used by botanists, physicists and ecologists to better understand the
natural world. But L-Systems has already had a huge effect on computer
programmers, 3D designers and virtual world developers today. Lindenmeyer’s
computer “language” inspired a new field within artificial life. Artificial
Life, commonly called ALife studies evolutionary agents or populations of
computer simulated life forms in artificial environments. ALife researchers use
three fundamental concepts essential to our understanding of structure and
processes of life: symmetry, complexity and self-similarity. They apply the
tools of L-systems to generate “life” in cyberspace as evolving virtual worlds. [6]
The Tree of Human Relationships
Trees of our Forefathers
The tree has
been used for hundreds of years to organize our genealogical histories. Our forefathers are the “roots” of our
branching family line, and the branches reflect our relationships to each other
with a similar, hierarchical beginning. Trees showed heritage to be related to
royal bloodlines and religious figures. By the 12th century, the Christian
religion emphasized the connection between the New and the Old Testament by
visually codifying the line of Jesus back to King David in illuminated “Jesse
Trees”. The Jesse tree is envisaged
to demonstrate the direct lineage between Jesus and the Prophets of the Old
Testament to prove he was a direct descendent. It
is based on the prophecy of Isaiah, "there shall come forth a rod out of the stem of Jesse, and a branch shall
grow out of his roots." [7] Yet even in biblical Jesse Trees, a pagan
female figure, the Cumaean Sybil was also included with the Prophets because
she had predicted the birth of a “messiah.”

The Jesse Tree of the Judeo-Christian Bible, depicted in countless illuminated manuscripts, paintings and stained glass windows chronicled the genealogy of Jesus up to the Father of King David. The Jesse Tree
as a structural metaphor continued to be used through the centuries by Royal
families. Royalty used consanguinity trees to understand lines of descent and
to determine whom they could marry.
Visually, these trees progressively went
from a literal to a more abstract form. In the tradition of the “Jesse Tree,”
royal consanguinity trees perpetuated the royal status of bloodlines by
conflating royal blood with religious and
royal decree. Consanguinity trees were theoretical diagrams of blood relations
showing who may marry and who may inherit.
Trees become Structures & Charts
A new symbol
system was created in the field of anthropology as an abstract diagram used to
demonstrate the many types of familial relationships within different cultures.
In the 20th century, anthropologists studying familial relationships through
“kinship charts” began to find numerous non-hierarchical and patriarchal
familial formations of bloodlines.

Cultural practice such as matrilineal and
avuncular family structures made us rethink
our linear, hierarchical categories and appreciate the diversity of family
structures and lines of descent.
Interest in
ancestry began to grow in the latter part of the 20th century. The power of the
World Wide Web in the 1990s unleashed an explosion of interest in personal
genealogical research that could be carried out from anyone’s home. Digital census records and historical
collections were brought into ancestry web sites for broad access to
information on the Internet.
Genealogy networks and software tools enabled thousands of people to
trace their ancestry and link to others with the same lineage. Family tree
templates, charts and software make it easy to input family information, share
and display it with others. Many of these contemporary family trees use more
radial abstract tree diagrams than the elaborate heraldic structures of the
past.
Dynamism and Dimension
The Internet
revolution has changed the basic nature of our personal and community
relationships. Humans are collaborating and communicating with each other;
mapping relationships has gone beyond genetic heritage and geographical locations
on Earth to include complex and overlapping sets of networks. As we communicate globally and
instantly with each other through email and social media, our game consoles,
PDA’s and IPhones, our relationships increased and global communities of
students, scientists, friends and international business colleagues have
emerged.

Our hierarchical
trees of human relationship were turning ever more radial with the rise of global
communities coming out of enhanced synchronous and asynchronous communication
via the Internet, Now we have numerous dynamic graphs of social networks, where
we can see “communities” linked by affinity rather than by geography or blood.

Social groups
are now linked by interest, affinity and knowledge. These groups can include
thousands of people. We can learn about our transforming culture by analyzing
these new social groupings. We now want to “see” how our new communities
congregate in cyberspace compared to relationships in the physical world, and
how subgroups arise, branch off and change through time. As Web 2.0 applications, social
networking and microblogging hubs like Twitter, FriendFeed and Facebook scale
out, each and every one of us can now see affinity “friendship networks” of our
contacts in the real and virtual environments. New visualizations such as
Twitter’s tweetmaps and Facebook’s friendwheels are based on branching tree structures that have become increasingly abstract,
nonlinear, and dynamic. These radial wheels also show how our networks of
associations are interconnected, demonstrating that we are all linked to each
other by less than “six degrees.”

With the advent
of social networking and blogging, digital mapping tools are now being merged
with blogs and network hubs such as Friendster, LinkedIn and Facebook. In 2006
IBM released ManyEyes, a Web 2.0 site a number of visualization tools anyone
can use to visualize their own data and share it with others. [8]
Since that time, the toolset behind ManyEyes has been integrated with
interactive news hubs such as the New York Times Visualization Lab. This way,
users can create and share their own visualizations with up-to-the-minute
statistical data from New York Times Stories. Social network tools are now
changing rapidly with an explosion of shared data and locative information from
myriad sources. Expectations for
the emerging Semantic Web suggest that this new level of ontologically
networked information will enable us to visualize even larger meta-networks of
relationships. These
visualizations will provide new insights about the complex, emergent
organization of our growing communities and the knowledge these communities
share.

The Tree of Knowledge to Mapping Knowledge Domains
Structuring Knowledge with Arboria
In addition to
mapping relationships, humans have also used trees or “arboria” to structure
knowledge and organize ontologies.
Going back Aristotle’s categories of logic, third century Neoplatonist
philosopher Porphyry visually codified these categories into a tree structure
that was later called “Porphyry’s Tree.” The terms ‘genus’ and ‘species’ used
by Darwin and Haeckel for their scientific Tree of Life derived their use from
the more ancient practice Porphyry used to trace relationships between abstract
dichotomies (genus differentia) and their sources (species).
The Tree of Life
and Porphyry’s Tree further influenced medieval thinkers to use trees to
identify relationships between different categories or types of knowledge. In
the 6th century, Bishop Isidore of Seville used trees to organize his
encyclopedia, “Etymologiae” and Catalan mystic and philosopher Ramon Llull
followed suit by using Porphyry’s structure to depict the disciplines of
knowledge as Ars Sapientiae, or Tree of
Knowledge. The model of
Porphyry’s Tree was also used in tree diagrams for medieval religious books.
Trees of Virtues and Vices were used to visually diagram moral stories in the
life of Jesus, dichotomizing good and bad.
Trees were also used by later
writers, delineating the structure of book sections or geometric classes such
as Luca Pacioli’s Tree of Proportions in his book on the Divine Proportion, De
Divina Proportione, published in 1509.
Over the following several centuries, trees continued to be used to organize categories of knowledge, topics and subjects in encyclopedias.
Organizing the Data Deluge
In today’s digital culture, the current profusion of data requires us to find new ways to organize vast amounts of information: to see more at once, to allow for numerous the points of view (POV), and to introduce dynamism in our models. In order to do this, the metaphor of the tree has brought us from linear trees to cone, spherical and hyperbolic trees. The use of the tree structure continued through the 19th, 20th and 21st century as a way to organize knowledge and our web site directories.
In 1991, Stuart Card and his team at Xerox Parc introduced dynamism to the tree structure by creating “cone trees” that could be rotated. These trees moved away from the top down linear structuring, but allowed multiple views and the ability for the user to spin the cone tree around to see all the data.
Three university students who worked at Xerox Park—including visualization pioneer Ramana Rao—were inspired by the nonperiodic tilings-based artworks of artist M.C. Escher to try to create a dynamic way to visualize a tree of related information or content. Influenced by the hyperbolic math that MC Escher used (which was actually enhanced by Escher’s discussions with geometer Donald Coxeter while he was creating his artworks), Rao and his colleagues created a browser interface that would enable each chosen node to become the center around which all the other connected nodes would be organized. This became the first hyperbolic tree browser through Rao’s company, Inxight Software, Inc.
Along with social relationships, the nature of human knowledge began to change with the advent of the World Wide Web. Today, we have too much data and it is changing too fast for us to stay current. It is important to have simple ways to navigate and visualize connections between ideas, information and domains of knowledge. We can do this by revolutionizing the way we look at data by visualizing its larger patterns.
As our knowledge increases on the Internet and access to massive databases of information must be analyzed, classified, accessed and understood, we need new structures to envision broader swaths of knowledge, its creation and evolution. In the first decade of this century, Dr. Katy Borner, Chaomei Chen and Kevin Boyack pioneered a new direction for visualization as applied to “domains of knowledge” by mapping the growing domain structure of scientific disciplines through citations indexes.
Research
& Node Layout: Kevin Boyack and Dick Klavans Map of Science, 2007; Data: Thompson ISI; Graphics & Typography: W. Bradford Paley;
Commissioned Katy Borner at Mapping Science. www.scimaps.org
Boyack’s work with Richard Klavans has undergone almost a decade of refinement in the visual metaphors used for these structures, becoming less and less hierarchical and more natural, almost biological in shape. These new science maps are based on hundreds of thousands of citations and are analyzed and visualized to identify emergent paradigms of scientific knowledge domains.
Now that
visualizations can illustrate the radial patterns and connections between
different types of knowledge, we are able to see relationships between
disciplines again. The branching
connections and overlaps between research is highlighted in a new kind of
mapping developed by a cluster of scholars and leaders in the field of
information visualization. These
are called “Knowledge Domain” maps. [9]
A New Aesthetics for Knowledge Visualization
“Knowledge domain” visualizations have become a growing genre now known as “Science Maps.” A new information aesthetics defines the way to show metrics across a broad range of source material. More cross fertilization between disciplines is seen. More data is being generated collaboratively in the public domain. Using a public Wikipedia “data dump” in 2007, Borner, et.al. applied knowledge domain visualization methods to understanding how science, math and technology are represented in Wikipedia - showing where they cluster and where they overlap.
Although the Wikipedia map of science is just a snapshot of Wikipedia at a moment in time, eventually such “maps” will be able to be used as dynamic interfaces into huge repositories of shared information. As we move further into the dynamism and non-linearity of collaborative information, visualization tools are being created to visualize knowledge “flows” over time through new kinds of visualization such as those by Moritz Stefaner’s Well-Formed Eigenfactor.

A new aesthetics
of data visualization is emerging. The universal image of the tree has
transformed from a natural form that was used as a mythical image, a visual
metaphor, a symbol, a dynamic organizing structure for information, and
finally, an algorithm that generates lifelike trees in virtual space.
The tree
structure has morphed from a static image to a dynamic way to look at the
changing patterns in large amounts of data. As we used the tree to map relationships between humans and
knowledge, our tree patterns evolved from a linear 2-dimensional tree to radial
tree to a 3-dimensional sphere tree. Now we can return to the original mythical
images of the World Tree and the Tree of Life and take these tendrils out
further to the Global Mind.
Shape of Thought Mural, Clegg & DeVarco, 2009/2010
The
rapid growth of social media and knowledge domain mapping is changing the way
we communicate our relationships, our knowledge, and our relationship to our
planet. As the streaming, conversational network of the realtime global
community grows, the only way we can see our organizational forms from a
“satellite view” is to use visualization tools.
These dynamic tree structures and new visualizations can be thought of as a small world networks.
These are mathematical graphs of networks. In the burgeoning field of network
theory, which builds on early work by social psychologist Stanley Milgram in
1967, everyone is connected to everyone else by no more than six degrees.
Milgram postulated that networks of clusters are connected to other clusters
with very few bridges, connecting all the nodes between. We can think of this
as a number of linked or nested tree clusters. In the “Six Degrees of Kevin
Bacon” game, this idea was born out and popularized.
The
“Oracle of Bacon” game was more than just a popular game. It influenced
mathematician/physicists Duncan Watts and Steven Strogatz to establish the
mathematical principles whereby Small World Theory could be rigorously proven
as a class of random graphs. This
complex systems algorithm initiated the new “science of networks” that allows
scientists to better understand collective dynamics through graphing techniques
or complex tree structures. Similar dynamics can be seen in any type of
network. Physicist
Albert-Laszlo Barabasi later proved that the distribution of these networks
follows a specific power law, and this common blueprint can be seen in a vast
array of networks – from intra-cellular protein networks to human social
networks. Network theory is now
able to be put to pragmatic use for everything from
computer viruses to human behavior. Scientists led by Alessandro Vespignani
have recently used network algorithms to map how patterns of global
transport networks can help us quickly respond to pandemic outbreaks. [10]
From the Kevin Bacon game to a game changer for humanity, small world network theory and its emerging class of visualization technologies offer new ways of thinking and “seeing” that amplifies our human ability to share knowledge for global self-reflexivity. What began with the tree metaphor has become instead a dynamic language of patterned networks of whole systems behavior – systems of life, knowledge and relationship.
“These patterns are biological, they are scale independent – the patterns we see when we use our powerful lenses to explore the outer reaches of the cosmos and the inner dimensions of the cell. Visionary language mirrors the history of knowledge, the neurostructure of synaptic behavior, the self-assembly of crowd consciousness, the ubiquitous mobility of swarm behavior, the ephemeral architecture of smart mobs. But it does more – it mirrors the span of self-awareness to mass introspection by engaging our emotional intelligence through the act of seeing our reflection. In the words of biologist Barbara McClintock, it offers us “a feeling for the organism.”"[11]
Through the evolution of the Tree of Life, the Tree of
Human Relationship and the Tree of Knowledge, we see the story that brought us
to today’s visualization
technologies reflecting the ‘superorganism’ of collective thought.
*****************************************************
FOOTNOTES:
[1] See more about the Shape of Thought Approach "What is the Shape of Thought?" Clegg & DeVarco
[2] From the online New World Encyclopedia – Judeo Christian Tree of Life
[3] http://tolweb.org
[4] Lindenmeyer, Aristid and Przemyslaw Prusinkiewicz. 1990. The Algorithmic Beauty of Plants. Springer-Verlag
[5] 1,2,3,5,8,13,21,34...
[6] Storyboard for UCSC Virtual High School Complexity Gallery
[7] Isaiah 11:1. The New International Version of the Bible
[8] See more about ManyEyes
[9] Borner, Katy, R. Schiffrin, "Mapping Knowledge Domains," Proceedings of the National Academy of Sciences (PNAS), Jan. 23, 2004.
[10] See more at: Scholarly Networking to Stop Disease which features the work of A. Vespignani, S. Sherman and K. Borner.
[11] DeVarco, B. “A Visionary Language.” Scale Independent Thought Blog Jan 2, 2009.