Elements of Dynamic Network Analysis: 3. Connecting the dots

John Terrell

Categorical thinking, which I wrote about in the first two posts in this series, may at times be too pat for our own good, but this pragmatic (although potentially knee-jerk) way of dealing with things, people, and events is rarely based solely on nonsense.

Old-fashioned library card catalog [https://www.flickr.com/photos/mamsy/ [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons]
Why not? Because the world is not an entirely unpredictable place. What happens to us, good or bad, is seldom purely random or plain crazy.  Life actually does have patterns that can be real enough, although they can also be far from  clear-cut and hard to see. Even so, patterns can be categorized. Not always successfully (just ask any weather forecaster), but that doesn’t mean we shouldn’t try to do so.

But this is enough about categorical thinking for now. I want to move on and write instead about what I have previously referred to as relational thinking.

Relational thinking

The National Council of Teachers of Mathematics defines this way of thinking as the “mindful application of place value and the properties of number, operations, and equality in solving mathematics problems.” If this confuses you as much as it does me, note this organization adds: “A student with a disposition toward relational thinking has a habit of thinking before acting.”

This seems like an uncommonly low bar. Certainly not the definition I have in mind. Nature‘s online magazine Science of Learning offers an alternative: “At the core of all human learning and  performance  . . .  is the foundational ability to perceive patterns that thread through all of nature, including human nature.”

This isn’t quite it, either. In fact, to me this sounds more like a definition of categorical thinking. So let me give you my own take on what pairing these two words together means:

Categorical thinking assumes that things exist apart from one another, and may then become connected with one another.  

Relational thinking assumes instead that things exist because they are connected.

If my definition sounds too mystical to you, let me offer you several examples of what I mean.

One-sided relationships

It seems likely that no relationship is solely one-sided if looked at closely enough. While granting this likelihood, there is no doubt that relationships can be so out of balance that it is not just a technicality that one side is more influential than the other. Critically, the character and perhaps the very existence of one side in such an imbalanced relationship may depend, maybe entirely, on the relationship it has with the other side.

A classic example of such a one-sided connection is the relationship between the Sun in our solar system and all the other planets (and then some) revolving around it, including Planet Earth.

Even without venturing into the exotic realm of modern cosmological theories about quantum gravity, it is obvious enough nowadays except perhaps to those who believe the Earth truly is flat that if it were not for the gravitational relationship between the planets and our Sun, the Earth would not exist at all and neither would we. Our reliance on the Sun is that one-sided and decisive. There would also be no life at all on our planet without the Sun serving as life’s ultimate source of energy, however otherworldly such a statement may sound.

Technical note: In formal network analysis, a relationship between two things (the two nodes or vertices in the relationship) is said to be dyadic (two-sided). When both are taken together, they are called a dyad. Furthermore, such two-party connections can be either undirected (more or less balanced or symmetrical from the point of view of each), or they can be directed (each party has a different take on the relationship). From this perspective, the relationship between the Earth and the Sun is a directed dyadic relationship, and it is a relationship that is decidedly one-sided.

Photo via Good Free Photos
Two-sided relationshps

It has been said that human beings have an innate sense of fairness and an ingrained willingness to do something for others when they are reasonably confident that a favor, whatever it is, will be returned, if not in kind, at least in some other way having equal value.

This judgment of our willingness to engage with others in two-sided relationships is far too cynical. Available evidence suggests instead that most of us are basically predisposed to be kind, collaborative, and helpful to others. That’s how we have evolved as a social species.

Moreover, humans as a rule are not only ready, willing, and able to forge and maintain relationships with others. We are also remarkably skilled at coming up with playful excuses to do so.

Although jogging, bicycling, and other forms of exercise, for instance, can be done easily enough as solitary tasks, people often find ways of turning even such seemingly self-centered healthy activities into broadly social occasions.

Although a more sedentary activity than a physically healthful one, this observation holds true also for online computer gaming, which is now a major leisure-time social activity for millions around the globe.

Technical note: A racket sport such as tennis is an example of an undirected dyadic relationship (accepting, of course, that only one of the players can win). Yet tennis is also a spectator sport, and as such, creates a directed dyadic relationship between sports fans and players.

Many-sided relationships

It is obvious enough that spectator sports such as tennis or baseball involve more than just simple dyadic relationships between players and spectators. The social complexity of team sports is even more apparent for sports such as soccer and football that call for the coordination of players both within and between the two opposing teams on the field.

A friend in need, 1903 [Public domain, via Wikimedia Commons].

Side note: There seem to be few team sports that call for more than two teams on the playing field at the same time—maybe they should be called “dyadic sports”—although a few examples do come to mind if you are willing to bend the definition of what is a sport: many kinds of card games, many types of board games, some varieties of billiards, some forms of bicycle racing, etc. 

But the many-sided complexity of most human relationships isn’t just obvious while watching  players interact with one another on a playing field. The general complexity of human relationships is more than apparent also among the fans watching the game being played right there before their eyes. Indeed, in the case of some sports, it could  be argued that “most of the action” is actually in the bleachers, not down on field. (You may be able to tell I don’t like baseball, and I am not too fond of football, either.)

Tim Beckham, catcher John Hicks, umpire Roberto Ortiz in a 2017 game [Keith Allison from Hanover, MD, USA (Tim Beckham) [CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons
How can we tackle the complexity of human relationships?

Classic definitions of social network analysis as a way of coming to grips with the complexity of human social relationships commonly read like this one from John Scott’s highly successful book Social Network Analysis: A Handbook: “social network analysis is an orientation towards the social world that inheres in a particular set of methods. It is not a specific body of formal or substantive theory” (page 37, 2nd ed., Sage Publications, 2000).

I find such a view naive, however well-intentioned. It is quite impossible to isolate methods from theories and then claim to be doing good science. This is an observation I will explore further in the next posting in this series.

This is Part 3 of a continuing series of posts on dynamic network analysis. Next up: 4. Exploring the 5th dimension.


© 2018 John Edward Terrell. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. The statements and opinions expressed are those of the author(s) and do not constitute official statements or positions of the Editors and others associated with SCIENCE DIALOGUES.

Elements of Dynamic Network Analysis: 2. Relativity

John Terrell

In the inaugural posting in this series, I made note of the fact that history shows us time and again that as a species we have decided strengths and obvious weaknesses.

Why it’s good to be human

On the plus side, our kind of animal is outstanding at reshaping and rebuilding the world around us to make the challenges we face as individuals and as a species as humdrum, predictable, and hence as manageable as possible.

Poets, playwrights, philosophers, and scientists may debate the particulars of human motives and intentions, but there is no denying one of the reasons we spend so much time and effort at redoing the conditions under which we live out our days on earth. The more predictable a situation or event is, the easier it is for our brain to cope with it. And if need be, respond more or less appropriately.

Spice Bazaar, Istanbul [personal photograph]
I also argued in the previous post that to avoid becoming overwhelmed by what our body’s senses—classically said to be five in number—are telling us about the state of things and events both inside and outside our skin, our brain ignores much of what it is being told. Instead it mostly relies on the pragmatic strategy of simplifying what it is hearing, both literally and figuratively, by mentally putting things, people, and experiences into separate and seemingly distinct mind boxes—into different categories.

However, there is a fine line between paying too much attention to what our senses are telling us, and too little. (I like to call this the Goldilocks Line after the 19th century children’s story). Failing to pay sufficient attention to what’s happening inside or outside our body can be disastrous, as anyone who has survived the experience can tell us about why they shouldn’t have been texting while driving.

Why it’s bad to be human

As my mother so often liked to say, things can be both good and bad at the same time. However pragmatic and unintentionally self-centered we are as individuals for understandable evolutionary and psychological reasons, the dark side of our human ways cannot be denied.

I wasn’t being cynical in the previous post, therefore, when I remarked that truth may not be as appealing and important—that is, as useful—to us as human beings as the immediate and pragmatic benefits of things and events (and people, too) that are easy, convenient, and predictable.

However, taking the easy way out, the easy answer, the easy job, and so forth can be costly down the road—sometimes sooner rather than later. Doing so can make it difficult for us to notice and pay enough attention to how things, people, and experiences are linked, intertwined, and interrelated. Said more formally, what I called previously “categorical thinking” can lead to “categorical mistakes.”

The power of words

According to more than just a few of us, life’s big question is Why am I here? Others instead see How come I am here? as the mystery to be solved. Conventionally, people turn to theologians, philosophers, psychologists, and their best friends when they are seeking answers to the first question. The second one falls more in the thoughtful arena of pediatricians, scientists, cosmologists, mystics, and priests.

This division of labor, however, is not absolute, and is certainly not as categorical as such a divide implies.  One common thread crossing between these two realms of expertise is the belief or assumption—sometimes up front, sometimes only lurking in the background—that words are both powerful and are usually grounded in reality except, of course, when someone is “making things up” that they know are untrue.

The belief that words can be both truthful and powerful—that by naming things we are not just “putting into words” something already “out there” in the world, but can create something new as if “out of nothing”—is deeply rooted in the antiquity of our species. A classic example would be invoking the word abracadabra during a magic show to lend apparent substance to some clever illusion. But the roots of seeing words as powerfully creative run deeper than this trivial example.

The Almighty. Genesis cap 1 v 16. De Vos [By Phillip Medhurst [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], from Wikimedia Commons]
For instance, consider the opening words of the Book of Genesis in the Hebrew Bible and Old Testament:

IN THE BEGINNING God created the heaven and the earth.
2  And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters.
3  And God said, Let there be light: and there was light.
4  And God saw the light, that it was good: and God divided the light from the darkness.
5  And God called the light Day, and the darkness he called Night. And the evening and the morning were the first day.
Relational thinking

In my first post I said that I am writing this series about dynamic network analysis because I want to explore with you how a different way of thinking about the world and our place in it can make it easier for us to see and make something out of how widely and how often critically things, people, and events are not separate and distinct in neat categorical ways, but instead are interwoven into relationships that make the whole totality of them, as the saying goes, bigger than the sum of the parts. Since what I want to write about, however, is complicated, I need to proceed step by step.

The next step in this second post is a brief quiz I’d like you to take before we move on to take a closer look in Post #3 at what is called network analysis.

Quiz: How good are you at thinking outside the category?

Please take a piece of printer paper and draw a line down the middle from top to bottom. Near the top of the left-hand column, write the word categorical. Do the same for the right column, except make the word relational. Then write in items under these two headings matching those shown here. Note that the last two rows are blank. In a moment I will be asking what you would add in these two bottom rows resonating with the rows above them.

Here’s the question I want to ask: What makes the items in the right-hand column different from those in the left-hand column? Yes, it is OK to use Google if some of the items seem obscure. And yes, this is a categorical question for sure.

The answers I am looking for

There are many ways to talk about the items in the left-hand column.  #1-2 are often viewed nowadays as wasteful single-use items that pollute the environment; #3 is a famous writer who rejected the virtues of altruism, praised individual rights, and is seen by many as a prophet of selfishness; #4 is an organization dedicated to protecting the rights of individual gun owners; #5 is the day each year when a given individual was born; #6 refers to the belief that all things can be boiled down to singular, individual particles called atoms.

In contrast, paper bags and paper straws are being promoted today as more environmentally friendly than their counterparts in the left column. #3 could be described as the high priest of the relativity rather than the individuality of things in the universe. Without trying to pin them down, the remaining three items are similarly all about things, events, and species that are enmeshed with one another.

Now here’s your job. What would you write in the blank rows at the end of this table? For instance, I myself would be tempted to write in one of these rows the card game solitaire vs. the team sport of boat racing.

By National Library of Ireland on The Commons (Waterford Boat Club) [No restrictions], via Wikimedia Commons [https://commons.wikimedia.org/wiki/File:Waterford_Boat_Club_(8401799848).jpg]
What’s the point I am trying to make?

In the first post in this series, I observed that for entirely understandable reasons each of us is by nature self-centered. Saying this, however, does not have to mean we are also inherently selfish despite the fact that jumping to such a conclusion is unfortunately fairly commonplace even in scholarly circles.  

As we will be exploring in this series, Ayn Rand and others both before and since have been misguided to believe otherwise. The continuing popularity of Rand’s ideas only shows that words can be powerful at least in the limited yet dangerous sense that they can be used to persuade us about what’s real and what’s unreal in the world of yesterday, today, and tomorrow without actual proof.

This is precisely why we need ways of getting outside our heads and dealing directly with the world that force us to “think outside the category.” Why? Because we need ways to confront our hasty impressions, deep-seated desires, wishes, and wants so that we can avoid errors in judgment, however innocent, that tragically can result in the desecration of the world we live in—and if we are not careful, our own extinction as a species.   

This is Part 2 of a continuing series of posts on dynamic network analysis. Next up: 3. Connecting the dots.


© 2018 John Edward Terrell. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. The statements and opinions expressed are those of the author(s) and do not constitute official statements or positions of the Editors and others associated with SCIENCE DIALOGUES.

Elements of Dynamic Network Analysis: 1. human nature

JOhn Terrell

Human beings are by nature highly social animals. Despite claims both popular and scientific, we also are not inherently selfish creatures. Yet we often seem self-centered. Why? Short answer: because we are looking out at the world from inside our skulls.

As my mother used to say, this is both good and bad. Let me explain briefly by offering you a few elementary observations about being human.

Your pragmatic brain

A fully functioning human brain is a remarkable compromise. Your senses are constantly feeding you input—lots of it—about what’s happening in the world around you, and also about what’s going on inside your body. If your brain were to pay close attention to all the details it is receiving about the state of things within and beyond you, it would rapidly become overloaded. That, of course, would make it useless to you as an organ dedicated to helping you in an admittedly self-serving fashion navigate your way more or less successfully from the cradle to the grave.

It is perfectly understandable, therefore, why your brain perpetually walks a fine line between paying too much attention to what it is being told by its senses, and too little.

Figure 1. “I swear they came out the box this way | by frankieleon” [https://www.flickr.com/photos/armydre2008/3576170595]
One way the brain accomplishes this delicate balancing act is to put things, people, or events striking it as more or less like one another into the same mind box—that is, into the same mental category. By this I mean what a dictionary says this word means:  “a class or division of people or things regarded as having particular shared characteristics.”

well-known rule of thumb illustrates the point I am trying to make: if it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck. A more colorful example is shown in Fig. 1.

But here’s the rub. What if your brain draws the line between too much and too little in the wrong place? What if it doesn’t pay enough attention to what it is being told by your senses about the animal your brain has concluded must be a duck? More to the point, what if making such a categorical mistake leads to serious consequences? Say, mistaking a friend coming into a darkened room for an intruder. And impulsively you shoot your friend dead?

Clearly having a pragmatic brain lodged inside that bony vault up there on your shoulders can be both good and bad, just as my mother would observe.

A world of our own making

Here’s another observation about how humans deal with the world. If novelty is the spice of life, then from your brain’s pragmatic point of view, predictability is life’s bread & butter.

Put simply, the more predictable a situation or event is, the easier it is for your brain to categorize it. And then, if need be, respond appropriately (or not).

Figure 2. By Crusier [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], from Wikimedia Commons
It is again understandable, therefore, why as a species we humans invest so much of our time and effort (and money) into dumbing down the world around us to make the challenges we face as humdrum, predictable, and therefore categorical as possible.

By “dumbing down” I mean our species is remarkably skilled at remaking the world we live in to be less risky and uncertain than it otherwise would be for us. Said another way, we love to make what’s out there in the world fit into simple, convenient, widely applicable mind boxes, i.e., categories.

Humans are not the only creatures on earth who are predisposed to make the things and events they have to deal with as humdrum as they can make them. Many of the earth’s countless species are similarly committed in their own more limited ways—biochemical, physical, or behavioral—to enhancing their surroundings and creating favorable opportunities for themselves (we are not the only self-centered creatures on earth) by making things more suitable, more accommodating, more predictable. And for them, as well, more categorical.

This last remark is important, as I will be explaining in a later posting in this series. The brain's mind boxes called "categories" may or may not have actual words associated with them that we can use to talk about them. This is often why we may find it hard to put our ideas into words. But with this remark I am getting ahead of what I want to say in this first post. 

Figure 3. Termite mound, Litchfield National Park, Northern Territory, Australia [By brewbooks from near Seattle, USA (Cathedral Termite Mound) [CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons]
Classic examples of what other species do to dumb down the world for themselves would be beavers constructing dams to create ponds that help protect them against predators; termites building earthen mounds in Africa, South America, and Australia to live in; birds building nests; and earthworms improving the quality of the soil they move through by eating it and passing it through their bodies, over and over again, generation after generation, thereby making life easier and more fulfilling for the earthworms that take their place in the great circle of life.

Clearly, therefore, we are not alone as a species in being both able and crafty enough to improve our lives and living circumstances by making the world a safer and more predictable place to live in.

Even so, we humans are certifiably the Earth’s champions at the fine and skillful art of redoing the world to suit our needs as well as our fancies, however odd the latter may be (let’s all admit, shall we, that the artificial islands of the exotic tourist resort shown in Fig. 4 are an extreme example of our willingness to redesign the world to suit our fancies and our credit cards).

Figure 4. Palm Island Resort, Dubai, United Arab Emirates [https://commons.wikimedia.org/wiki/File:Dubai_-_The_Palm_Jumeirah_-_panoramio.jpg]
Confronting our pragmatic and often self-centered ways

We have reason, therefore, to be proud of the fact that our species excels all others at creatively dumbing down the world we live in to make the challenges we face humdrum and predictable. But there are genuine risks involved. Why so? Because we are not truly god-like in our powers. We are not all-seeing and wise. We are not always as good as we may think we are at drawing the line between knowing too much about the world and knowing too little.

And furthermore let’s be honest. Despite rhetoric to the contrary, truth (spelled with or without a capital “T”) may not actually be as appealing and important—that is, as useful—to us during our journey from the nursery to the grave as the pragmatic benefits and virtues of things and events (and people, too) that are easy, convenient, and predictable.

Here then is what this series of posts at SCIENCE DIALOGUES will be about:

  • Millions of years of evolution have done a skillful job of making us clever, inventive, and remarkably successful beings.
  • As history shows us again and again, however, our reliance as a species on the pragmatic (and generally self-serving) strategy of mentally putting things, people, and experiences into separate and seemingly distinct mind boxes—into different categories—often makes it hard for us to notice and pay sufficient attention instead to how things, people, and experiences are almost always linked and interrelated rather than separate and distinct. 
  • In this series, I will be calling the first brain strategy categorical thinking, and the second one relational thinking.
  • My goal in writing these posts will be to survey for you how the second way of thinking about the world and our place in it makes it easier for us to see and understand how widely and often critically things, people, and events impact one another—sometimes in unexpected and even disastrous ways (for example, see: Fig. 5).

Moral of the story so far: while understandable from an evolutionary and psychological point of view, being self-centered creatures is a handicap we humans need ways to confront and overcome.

Dynamic network analysis is one such way. I hope to convince you it is a good one, too.

Figure 5. The beach at Kanapou Bay collects debris from throughout the Pacific Ocean. [https://www.flickr.com/photos/noaaphotolib/19778606375]
This is Part 1 of a continuing series of posts on dynamic network analysis. Next up: 2. Relativity.
© 2018 John Edward Terrell. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. The statements and opinions expressed are those of the author(s) and do not constitute official statements or positions of the Editors and others associated with SCIENCE DIALOGUES.

Elements of Dynamic Network Analysis: a new series

John Terrell

During the second half of 2018 SCIENCE DIALOGUES will be featuring a series of reports on the steps that have been taken at the Field Museum in Chicago since the early 1970s to develop dynamic 4-dimensional (space-time) approaches to networks analysis in the social and historical sciences. 

The goal of these reports is to prepare the way for writing a book about how networks analysis is currently revolutionizing scientific (and hopefully human) thought about the world we live in and our place in it.

The first posting in this new series on human nature is available here along with a link to the second post  now online at SCIENCE DIALOGUES.


Cover art (a fantasy) for the proposed book on networks thinking.

Zambia paleo dig yields new insights on Permian-Triassic environments

Mark Alvey

Please note: this news story, recovered on 28-Jan-2017, was originally published in Science Dialogues on 27-August-2014.

Ken Angielczyk in the Luangwa Basin of Zambia holding two specimens of the dicynodont Diictodon. Photo by Roger Smith.

Associate Curator Ken Angielczyk of The Field Museum was part of an international team of collaborators that conducted paleontological fieldwork in Zambia between June 22 and July 31. Ken and his collaborators focused on Middle Permian (~265 Mya) to Middle Triassic (~240 Mya) rocks in two areas of the country, the Zambezi Basin in southern Zambia and the Luangwa Basin in northeastern Zambia. The team had done preliminary work in the Zambezi Basin in 2011 and 2012, but only spent a total of about 5 days working there. This time, they spent about two weeks there and their discoveries include multiple species of archaic amphibians and dinocephalians and dicynodonts (both ancient mammal relatives) from the Middle Permian, extremely well preserved fossil wood, and evidence that two temporally-distinct faunas are preserved in the Permian rocks in the Zambezi Basin. They also collected a large amount of geological data that will help complete the picture of the environments in which the plants and animals were living.

Ken’s colleagues Sebastien Steyer and Charles Beightol excavate a dinocephalian skeleton preserved in Permian rocks in the Zambezi Basin of Zambia. Photo: Cristian Sidor.

The team had conducted more extensive fieldwork in the Luangwa Basin in 2009 and 2011, and this year their work focused on rounding out their previous collections and collecting more geological data to understand  paleoenvironments. Among their discoveries is evidence of strong associations of particular dicynodonts with specific environments in the Late Permian rocks of the Luangwa Basin, and strong evidence of increased aridity and changes in the nature of river systems in the area moving from the Late Permian to the Middle Triassic. Ken and his collaborators will use these data to investigate the role environmental changes played in shaping the end-Permian mass extinction (the largest extinction in Earth history) and the recovery following the event.

Ulemosaurus svijagensis – primitive tapinocephalian from Middle Permian of Tatarstan. Illustration by Dmitry Bogdanov. Source: https://en.wikipedia.org/wiki/Ulemosaurus#/media/File:Ulemosaurus22DB.jpg.

And one important result of fieldwork like that: scientific publications.  Ken and colleagues have a paper in the July issue of Journal of Vertebrate Paleontology describing fossils of tapinocephalids from Southern Zambia.  Tapinocephalids are hippo-sized, herbivorous mammal relatives that lived about 265 million years ago; the fossils were discovered by Ken and his collaborators during short exploratory trips to the Zambezi Basin in southern Zambia in 2011 and 2012. They are the oldest known tetrapod remains from Zambia, and demonstrated the potential of the area for further paleontological exploration (as in previous item). This is also the second time that Ken and his teammates have discovered tapinocephalids in an area from which they were previously unknown (the first time was in 2008 in Tanzania).

© 2014 Mark Alvey. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. The statements and opinions expressed are those of the author(s) and do not constitute official statements or positions of the Editors and others associated with SCIENCE DIALOGUES

Social network analysis: Hypothesis testing and what-if projections

John Edward Terrell

Please note: this commentary, recovered on 28-Jan-2017, was originally published in Science Dialogues on 13-June-2014.

GIVEN A RELIABLE DATABASE of information and a good computer program (such as Microsoft Excel), it is possible today to simulate a broad range of hypothetical real-world situations under differing possible opening and subsequent conditions (Embrechts and Hofet 2014). Said differently, by changing the parameters and values of a spreadsheet in meaningful ways it is possible to do informative what-if analyses of many kinds of situations—thereby gaining better understanding not only of possible but also plausible outcomes.

Similarly, it is possible to use a good network analysis program (such as UCINET; Borgatti et al. 2013) to simulate differing social situations and their plausible impacts. Here briefly described is one example based on research currently being done to explore the history of social networks along the north coast of Papua New Guinea.

Research question

During the last glacial maximum (~21,000 BP), sea-levels were ~125 m (410 ft) lower than they are today. It is likely that New Guinea’s northern coast was mostly a steep rocky shoreline offering few resources supporting human settlements (Chappell 1982).  As one consequence, New Guinea during the last Ice Age served more as a vicariant barrier than a land bridge between Asia and island Oceania (Terrell 2004).

Figure 1. New Guinea is the second largest island in the world. The northern coastline is over 1,600 miles (2,600 km) long. Shown here in comparison with the 48 mainland states in the U.S.A.

Both historical and archaeological evidence (Welsch and Terrell 1998; Terrell and Schechter 2011) suggests that villages on the northern coastline of New Guinea and the nearby offshore islands have been linked with one another by far-reaching social and economic networks for the past 2,000 years. An obvious and historically important question, therefore, is whether people and places there in the more distant past were similarly integrated in comparable widely-distributed communities of practice (Terrell n.d.).After the last Ice Age, however, sea levels rose steadily and then began to stabilize around their modern levels ~6,000–7,000 years ago. The resulting formation of coastal plains and environmentally productive lagoons and estuaries led to peak biodiversity (Hope and Haberle 2005) and probably also peak human population densities along this coastline between ~4000–2000 BP.

Materials and methods

Figure 2 shows two mini-max networks (Cochrane and Lipo 2010) drawn using UCINET 6 (version 6.289) and NetDraw (version 2.109) with the edges weighted at two different thresholds. The upper network shows the connectivity of places in this region given a maximal customary voyaging distance of 220 km or less—the greatest distance known to have been locally traversed during the Pleistocene and the mid-Holocene prior to ~3300 BP (Golitko and Terrell n.d.). The lower network has a threshold of 360 km—the greatest voyaging distance (from Makira-Ulawa in the Solomon Islands to Temotu in the Reefs/Santa Cruz group) documented as having been crossed during the first settlement of Remote Oceania ~3300–3100 BP (Irwin 1992).

Also shown in this figure are (a) the network positions (blue) of this region’s major sources of obsidian, a volcanic glass widely transported both historically and prehistorically in this region of the world; and (b) the location of our study area (red) on this coast in the Aitape district (Terrell and Schechter 2011).

Figure 2. Connectivity of obsidian sources (blue nodes) and Aitape (red node) on the Sepik coast of Papua New Guinea. Top: when the edge distance is 220 km or less; bottom: when it is 360 km or less (baseline image source: Mark L. Golitko). Likely cut lines in these networks projected using the Girvan-Newman algorithm (Girvan and Newman 2002) are shown here as heavy black lines. The same four groupings in the upper mapping occur at any assumed what-if linkage distance between 186 and 270 km.
Network analysis

Given these analyses, it is readily apparent that the what-if connectivity of these mappings differs markedly. Under the upper scenario, it can be hypothesized that obsidian from sources southeast of Aitape (they are on New Britain Island) has probably been transported from place to place at least as far west as Aitape, but it is less likely that obsidian from the other sources—located in the Admiralty Islands—has also arrived there despite the fact that these sources are geographically closer to our study area. The situation is different in the lower mapping. Instead of four probable groupings within the network shown, there are only two, and given this scenario, when obsidian has reached Aitape, it is more likely to have been mined at the nearer Admiralty sources.

Hypothesis testing

The presence of Admiralty Islands obsidian at prehistoric sites has not been securely documented archaeologically outside the Admiralty Group earlier than the mid 2nd millennium B.C. Its widespread popularity at Aitape and elsewhere in this part of the world thereafter is generally associated with suspected improvements in canoe-making design and technology thought to have been introduced from Island Southeast Asia around this same time (Specht et al. 2014; Terrell n.d.). However, it is also generally accepted that the movement of animals, obsidian, and people between islands and coastal villages was characteristic of life in this part of the world for many millennia before then—in other words, the suspected improvements in watercraft design and voyaging prowess did not initiate coastal and inter-island mobility in this region but instead made longer-distance travel more feasible and routine (Specht et al. 2014).

Figure 3. The actual geographic locations of the obsidian sources (blue dots) and the study area (red dot) at Aitape on the Sepik coast of Papua New Guinea.

While obsidian from Admiralty sources has been found at archaeological sites on the north coast of New Guinea that are younger than ~2000 BP, almost all of the obsidian that has been recovered archaeologically on mainland New Guinea older than ~3,500 BP has been sourced to the the Kutau/Bao locality on the Willaumez Peninsula of western New Britain (Summerhayes 2009).

Our fieldwork at Aitape in 1993/1994 and 1996 supported by the National Science Foundation ((BNS-8819618 and DBS-9120301)  discovered large quantities of obsidian and chert at localities along the former mid-Holocene shoreline (which at Aitape is now located several kilometers inland) including assemblages with notably high frequencies of  obsidian from New Britain marked by large average flake sizes (Golitko 2011)—an archaeological signature consistent with pre-2000 BP obsidian assemblages found elsewhere in northern Melanesia (Summerhayes 2009).

Therefore, given our two what-if network analyses and this archaeological evidence it may be hypothesized that obsidian has probably been indirectly available to people living in what is now the Aitape district ever since the stabilization of world sea levels around 6,000–7,000 years ago, but it is likely that the major sources of this natural glass prior to ~3,500 BP were those located on New Britain.

With funding from the National Science Foundation my colleague Dr. Mark Golitko is currently (June–July 2014) leading a research team at Aitape that is surveying archaeological sites there on the mid-Holocene (~5000 BP) shoreline (as reconstructed from estimated local uplift rates and sea-level records) to document how far-reaching or alternatively how restricted were cultural and material exchanges on this coast at that time. Discovering how isolated or widely linked communities at Aitape were during the mid-Holocene is  critical to understanding the patterning of modern human diversity in northern New Guinea and elsewhere in the Pacific (Terrell 2010a, 2010b).


Obsidian has long been a popular although largely nonessential raw material in the Pacific (as elsewhere on earth) despite the fact that alternative and equally useful cutting materials (such as bamboo) are readily available. Hence the ancient transport of obsidian through inter-community networks is commonly interpreted by archaeologists as more a social phenomenon than a practical (“economic”) necessity (Torrence 2011). As suggested by the what-if analyses discussed here, we anticipate  that Golitko and his team will discover this summer that obsidian was reaching communities on the Sepik coast well before ~3,500 BP.

Funding for this research was provided by National Science Foundation Grant No. BCS-1155338–”Archaeological and Environmental Investigations along the mid-Holocene shoreline near Aitape, Northern Papua New Guinea,” Mark L. Golitko and John E. Terrell.

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