How Gaia Saved the Earth from a Cold Death

 

The Goddess Gaia in the form of the winter deity Khione, daughter of Boreas, the North Wind, and the Athenian princess Oreithyia (image by "Nobody-Important"). 

Earth is a fragile planet and it might freeze to a snowball if not taken care of. So far, the Goddess has done a good job at that but, at least a couple of times during the past few billion years, the Earth actually froze. Might that happen again? It seems that we were close to that just a few tens of thousands of years ago. Now, the problem doesn't exist anymore, with humans pumping zillions of tons of greenhouse gases into the atmosphere. And, who knows? Humans could be the tool used by the Goddess to avoid another "snowball Earth." But now we may have too much of a good thing and the Earth risks boiling. Hopefully, Gaia can take care of that, too.   

It is always amazing to realize how complex is the system that we call the "Ecosphere". And how the system's complexity keeps its parameters within the limits needed for life to exist and prosper. It is the concept of "Gaia" as it was proposed by James Lovelock and Lynn Margulis. The ecosystem is in homeostasis and tends to maintain relatively constant parameters by means of a tangle of internal feedbacks, as all complex adaptive systems ("CAS") do. 

But homeostasis doesn't mean perfect stability. The system's parameters may oscillate - even wildly - before the internal feedbacks can bring them back to the "good" values. Sometimes the system gets close to its limits and it may well be that, at times in its long history, the ecosystem risked going over the edge and then Gaia could "die." This seems to be a common destiny for extrasolar planets, as recently argued by Chopra and Linewaver.

A recent paper by Galbraith and Eggleston on Nature starts from these concepts, noting how the concentration of CO2 in the atmosphere never went below ca. 190 ppm during the past 800,000 years. That happened in correspondence with the lowest temperatures ever observed during that period: the planet was going through a harsh ice age.

This figure from a recent paper by Galbraith and Eggleston on Nature shows an interesting fact: the concentration of CO2 in the atmosphere never went below ca. 190 ppm over the past million years or so. Possibly, it touched the danger limit for the ecosystem to survive. For lower concentrations, plants wouldn't have been able to perform photosynthesis and the biosphere would have largely disappeared.

About these ice ages, there is an interesting point related to the system's feedback. The more ice there is, the more reflective the planet's surface becomes (more exactly, the planetary albedo increases). But, the more reflective the planet's surface is, the cooler the planet becomes. So, we have an enhancing feedback that may transform the whole planet into a single, frozen ball: "snowball earth". It has happened, although possibly not completely, at least twice in the history of Earth. It was during the period we call, appropriately "Cryogenian," from 720 to 635 million years ago. It was not a real "snowball" -- not all of Earth was covered in ice. But what was not under the ice was a frozen desert. To give you some idea of the fascination of this subject, here is an excerpt from the abstract of a paper by Hoffmann et al. on "Science"

"....the small thermal inertia of a globally frozensurface reverses the annual mean tropical atmospheric circulation, producing an equatorial desert and net snow and frost accumulation elsewhere. Oceanic ice thickens, forming a sea glacier that flows gravitationally toward the equator, sustained by the hydrologic cycle and by basal freezing and melting. Tropical ice sheets flow faster as CO2rises but lose mass and become sensitive to orbital changes. Equatorial dust accumulation engenders supraglacial oligotrophic meltwater ecosystems, favorable for cyanobacteria and certain eukaryotes. Meltwater flushing through cracks enables organic burial and submarine deposition of airborne volcanic ash. The sub-glacial ocean is turbulent and well mixed, in response to geothermal heating and heat loss through the icecover, increasing with latitude. Terminal carbonate deposits, unique to Cryogenian glaciations, are products of intense weathering and ocean stratification. "

Can you imagine the Earth in these conditions? A wasteland of dry deserts and ice sheets. At that time, there were no multicellular creatures and life may have survived in hot pockets, maybe volcanic lakes, where it was still possible to find liquid water. 

We may have been dangerously close to a new snowball Earth episode during the past million years or so. Not a trifling matter because today the ecosphere is much more complex than it was at the time of the Cryogenian. A new snowball Earth would likely cause all vertebrate lifeforms to go extinct. It is not just a question of being too cold: the limit of concentration of CO2 that permits plants to perform photosynthesis at a reasonable rate is considered to be around 150 ppm, at least for the most common kind of plants. Under that value, all multicellular plants die, and with them all animal life. Only single-celled creatures could eke out a precarious existence in those conditions. 

But something prevented the ice sheets to expand all the way to envelop the whole Earth and, at the same time, prevented the CO2 concentration to go below 190 ppm. What was that? Several hypotheses are possible. Galbraith and Eggleston favor a biological one, saying that:

In terrestrial ecosystems, carbon fixation by plants is limited by low ambient CO2 (ref. 31). On this basis, ref. 12 proposed that CO2-limitation had significantly reduced plant-mediated silicate weathering during low-CO2 intervals of the past 24 million years, thereby enforcing a lower bound on the ocean–atmosphere carbon inventory over >10^5 yr timescales. Subsequent experiments have been consistent with this ‘carbon starvation’ mechanism, showing reduced weathering by tree-root-associated fungi under low CO2 (ref. 32). Although the feedback on silicate weathering would appear too slow to play a role on the 104 yr timescale of glacial CO2 minima 30, it may be possible that strongly reduced weathering rates lowered ocean alkalinity (thereby decreasing CO2 solubility) on a millennial timescale. Alternatively, reduced photosynthesis rates during the LGM (last glacial maximum) would have slowed the accumulation of terrestrial biomass14, consistent with estimates for lower terrestrial primary production rates33. By slowing the accumulation of carbon in vegetation and soils, this would have provided a stabilizing feedback via an increase of the ocean–atmosphere carbon pool.

Complicated stuff, right? But, basically, the idea is that CO2 is slowly drawn down from the atmosphere by a reaction with rocks (silicates), forming carbonates. This reaction is called "weathering" and it is favored by plants, whose roots provide a good environment for it to take place. Fewer plants, less CO2 drawdown. At the same time, a smaller global biomass means that the quantity of CO2 stored in it becomes lower and this extra carbon most likely ends up in the atmosphere as CO2. So, there are two feedbacks embedded in the system that tend to stabilize its temperature. But, as you may understand from the text by Galbraith and Eggleston, it is even more complicated than this! In any case, these stabilizing geobiological feedbacks oppose the ice/albedo feedback and tend to slow down the glaciation before the two sides of the ice sheet touch each other at the equator. 

But suppose that the Earth really became the snowball that some studies claim to have observed: how did it recover? If it is frozen, it is frozen. Maybe not completely dead, but poor Gaia was reduced to a minor sprite inhabiting hot springs. How could Earth return to the lush ecosphere we are used to?

There is an explanation: it is because volcanoes do not care whether the Earth's surface is frozen or not. They continue pumping CO2 and other greenhouse gases into the atmosphere. Again from Hofmann et al. 

“If a global glaciation were to occur, the rate of silicate weathering should fall very nearly to zero (due to the cessation of nor-mal processes of precipitation, erosion, and runoff), and carbon dioxideshould accumulate in the atmosphere at whatever rate it is releasedfrom volcanoes. Even the present rate of release would yield 1 bar ofcarbon dioxide in only 20 million years. The resultant large green houseeffect should melt the ice cover in a geologically short period of time”[(69), p. 9781]. Because Snowball Earth surface temperatures are below the freezing point of water everywhere, due to high planetary albedo,there is no rain to scrub CO2(insoluble in snow) from the atmosphere."

Note one subtle detail: if temperatures were to go below the freezing point of CO2 (-78 C) even in small regions at the poles, that would form a nearly infinite CO2 sink. And that would be "snowball forever" -- maybe it would have made the Goddess Khione happy, but it didn't happen. Possibly, that was too cold even for a Winter Goddess!

In any case, it seems that CO2 was pumped into the atmosphere by volcanoes, maybe it was the work of the volcanic form of Gaia, the goddess Pele, known for her habit of taking lava showers. 

When the CO2 concentration arrived at levels hundreds of times those of the present-day atmosphere, the result was a cataclysmic rapid collapse of the glaciers and a rise in temperatures. Not only the Earth's ecosystem was saved from a cold death, but it rebounded spectacularly: it was now the time of the "metazoa," the formal term indicate animals. There came the Cenozoic, in which we are still living, with its incredible variety of lifeforms when plants and animals colonized the continental lands. 

You see how the job of Gaia is not so simple. it involves a delicate balance of many factors. Some tend to stabilize the system, while others tend to destabilize it. During the past 15 million years or so, cooling factors took the lead and slowly pushed Earth to lower and lower CO2 concentrations and, with that, lower temperatures.

 Image from Wikipedia Commons. The x scale is in million years from the present. Note the rapid cooling of the past million years or so.

We do not know exactly what caused the cooling, there are several theories. But one thing is sure, Gaia started feeling that it was too cold for her, even in her form of Khiome, goddess of ice. She could die and, this time, perhaps for good. 

(Image source)

So, it became imperative for Gaia to mobilize some of the geosphere carbon and push it into the atmosphere in the form of a greenhouse gas that would warm the Earth back to comfortable temperatures. The Goddess Pele was too slow for that, maybe she is now a little tired after blowing CO2 into the atmosphere for four billion years. So, maybe Gaia thought of a more creative solution. 

Why not use those clever monkeys which had just evolved in Earth's savannas to dig carbon out of Earth's crust, combine it with oxygen, and then pump it back into the atmosphere?  It worked: in just a few hundred years, the monkeys managed to bring back the CO2 concentration to the levels that were typical of Earth as it was a few tens of millions of years ago. 

It may be that, now, Gaia faces the opposite problem: those monkeys have pumped so much CO2 into the atmosphere that now we risk pushing the planet on the opposite side of a climate collapse, to a "hothouse Earth" that might kill the biosphere. Something like that happened with the great extinctions at the end of the Permian and the Cretaceous. Alas, life is difficult, but Gaia can cope. Does that mean getting rid of those pesky carbon-burning monkeys? Maybe. After all, Gaia is a Goddess, she ought to know what she is doing and she has no qualms when it is time to do what's to be done. She can find ways. 

(Image Source)

Searching for Our Ancestresses: A Travel to the Origin of Time

 

Emma Ardinghi, my great-grandmother, animated by deep-fake technologies. She was born in the 1860s and died in the 1930s. Not many of us have images of their ancestors of more than a century ago. But what if some ultra-advanced technology could show your ancestors all the way to back to the creation of the world? (image created on this site. To know more about Emma, see here.)

Let's imagine a magic trick, or maybe a time machine, or a DNA-reconstructing technology, or some unknown laws of physics. Something, anyway, that shows you your ancestresses, all of them, one by one in a long, long string of mothers that leads you far, far back in time, all the way to the beginning of life on Earth. You are looking maybe into a screen, maybe into a crystal ball, or maybe into the clear waters of a stream in the light of the Moon. Just imagine.

Ten Generations (250 years). This stream of ten generations lasts ten minutes, one minute for each ancestress. The first face is our mother, of course. You know her well. You see her as a young woman, as you saw her in many old photos. Then, there appears your Grandmother, again as a young woman. Maybe you met her, maybe you remember her only from some faded pictures. She looks a little like you, same skin color and same eyes. As new images appear, you see faces you had never seen. The parade stops with the face of a woman who is your ancestor of 10 generations ago. She was born around 250 years before you, in a century when almost everyone was a peasant and there existed no such things as electricity, cars, or radio and TV. She has the same skin color as you, the same shape of eyes and nose, and probably a similar hair color. Let's assume that she is from Europe or North America and, in this case, she is most likely white. She wears a long cotton skirt and a shirt under a wool corset. She also wears a head cap and wooden sandals, no makeup on her face, her only ornament is a hairpin that she uses to keep her hair in a bun. She looks strong, in good physical shape, not a trace of fat on her body. Her husband appears behind her, a peasant wearing simple clothes and wooden sandals. In the background, you see the brick walls of the house. The windows are small and have wooden shutters. In a corner, a large fireplace. Although she is linked to you by a series of ten generations, her genetic imprint on you has been so diluted that she doesn't look very much like you. Still, if you look into her eyes, you feel a certain kindness, a certain sensation of familiarity. From wherever the image comes from, she locks her eyes into yours and smiles before fading. 

100 Generations (2000 years). Now the images change on the screen every six seconds. In ten minutes you see a hundred ancestresses, one after the other, separated by about 20 years from each other. Tall and not so tall, with long hair, short hair, sturdy, thin, lean, smiling, or maybe sad. There is a certain continuity with these images, the skin color remains about the same as yours: if you are black, they are black, and if you are white, they are white. And if you have slant eyes, they have slant eyes, too. But if you are blond, or you have clear-colored eyes, you'll see this feature disappearing: the eyes of your ancestresses gradually becoming brown, and their hair turns dark brown or black. When you arrive at the end of the sequence, you see someone who lived around 2000 years ago, at the time of the highest glory of the Roman Empire. She looks sturdy, but a little worn out by work and fatigue. She may wear a linen tunic under a heavy woolen cape. She may be a citizen of a large city, or someone living in a small village.  Behind her, her husband shows up. He is wearing similar clothes, a tunic, and a woolen mantle. Behind them, a brick wall with no windows, a fireplace in a corner. You have a glimpse of a simple wooden bed and a door. She doesn't look very much like you but, as you look into her face, you note a certain fire in her dark eyes. She is proud to be a citizen of the city or of the village where she lives. She smiles with an air of satisfaction at seeing that remote descendant of hers. For a moment, you are lost in those black eyes of her, then she fades away, and the parade restarts.

1000 generations (15 thousand years). Now the faces flash even faster, less than one second after each other. You see flickering faces, giving you just a quick glance of a few details: a hairpin, earrings, and an especially bright smile. These women maintain the same skin color you have and the same eye shape. But they look robust and sturdy, in good physical shape. The flickering stops with a woman appearing in front of you, looking straight at you. Let's assume that she is white. She wears a jacket and a gown in tanned skin. Around her neck, a leather necklace with hanging ivory teeth, maybe of a shark. Her hair is black, kept together by a leather lace at the back. Around her, you perceive a hut made of animal skin, mammoth tusks planted vertically in the soil are holding the skins together and a fire is burning at the center. Behind her, you see her husband. He wears the same kind of leather clothes. You see a stone-tipped lance leaning against the leather wall, and you can almost smell the burned fat of the animals in the hut. You look at her face. She doesn't look like you, not at all. But she has a certain air of pride that you recognize as universal among humans. She smiles at you, she seems to be happy to see this descendant of hers that she sees for such a short time. Then, she fades away.

10,000 generations (150,000 years). It is a whirl of faces that you see dancing on the screen. What you notice most is how the skin of your ancestresses is becoming darker and darker. As the movement stops, you are looking into the face of a black woman. She has curly brown hair, black eyes looking straight into yours. She is tall, she looks athletic. She wears a necklace made with seashells and a leather belt around her waist as she stands in the bright sun. You know that she is living somewhere in Africa and, behind her, you see the blue of the Ocean. In the distance, the Savannah extends all the way to the horizon. Around her, you see stones arranged in circles, traces of a campground where she lives, together with her group. You see her man standing behind her. Like her, he is black, tall and athletic, wearing only a leather belt around his waist. He holds a stone-tipped spear in his hands. An abyss of time separates you from her, and yet, somehow you recognize each other. You look into her eyes, she looks into yours. She smiles, although she looks a little perplexed at seeing this weird descendant of hers, so remote from her. But she seems to know that her descendants will cross that vast desert, spreading in the Northern forests and everywhere on Earth. She smiles at you as she says something that you don't understand, but that may be a charm of good luck. You smile back as she fades away.

100,000 generations. (one million years). What you see now is a continuous transformation, a morphing. The faces of your ancestresses change, shrink, their bones shift, they develop a pronounced brow ridge. Their skin remains dark, and when the sequence stops, you are in front of the face of this remote ancestress of yours, separated from you by one million years.  You see her standing in the open, among rocks and animal bones. She is completely naked, her skin mostly hairless. She is not tall, but not so much shorter than you. Behind her, a flat Savannah's landscape with shrubs and isolated trees. She is different, alien, with her broad nose, her flat skull under her black, long hair. You know that she is a member of the species called "homo erectus," not the same species you belong to, and you are tempted to call her "female," rather than "woman."  And yet, she partakes something of the human nature, you can't miss that. She has round breasts, and rounded buttocks, a human trait that other primates do not share. Nearby, you see her man, holding a hand axe in his hands. She is linked to you by an incredibly long series of motherhoods, each one an improbable event, and yet that chain led exactly to you.  You think for a moment at how a hundred thousand times a man and a woman, your ancestors, mated to generate the unlikely series of creatures that led to what you are. You look at each other in the eyes. Across a huge chasm of millennia, she nods at you, smiling, a gesture unchanged over such a long time. Then, she fades away.

One million generations (10 million years). Now you are rushing to the remote origins of the creatures we call "hominina." As the face morphs in front of you, gradually it becomes something not fully human. The sequence stops as you are in front of a face. Still a face, yes, but not the face of a sapiens. You are looking at a female of a different species. She is hairy, small, and sitting in a forested area together with other members of her group. The male, behind her, is bigger than her, and he looks suspiciously in your direction. You know that these creatures are common ancestors not just to you, but also to chimpanzees and gorillas. She looks at you, tilting her head a little as if she were surprised. You smile at her, she does not respond in kind, but she smacks her lips in your direction. A kiss from an ancestress of you who lived 10 million years ago. Then, the image fades away.

Ten million generations (100 million years). Now the creatures you see morphing on the screen rapidly cease having a face, they now have a snout. You see furry creatures quivering on the screen. The sequence stops to give you a glimpse of a four-footed creature that looks at you, puzzled, for a moment, before scuttling away, disappearing among the vegetation. Was that your ancestress? Yes, she was.  

A hundred million generations (400 million years). Creatures smaller and smaller appear on the screen, they rapidly lose their fur, they become flat, lizard-like animals. Smaller and smaller, until they disappear and you are facing the seashore from an empty beach in the sun. You know that somewhere, under the surface, a female creature is swimming. An extremely remote ancestress of yours. 

A billion generations (one billion years ago). You are still looking at the sea. An ocean of time goes by and nothing happens. You only know that, down there, there is something alive, quivering, changing. Microscopic unicellular creatures are busy reproducing themselves by mitosis, splitting themselves in two. They are no more males and females, yet they are the origin of what you are, there, below the surface of that remote ocean. 

10 billion generations (5 billion years ago). Now the view moves underwater. In the darkness, you dimly perceive submarine mountains spewing gas bubbles everywhere. You know that those mounds are the factories where organic life is being created. It is strange to think that your so-remote ancestor is not anymore a living creature, but an organic molecule. As you watch, the sea boils in a great turmoil as you enter the Hadean, the age of hell. Then, everything fades into darkness. Before the scene goes away, you have a glimpse of large, bright eyes looking at you. The Goddess herself is there, dancing in the emptiness of space while she creates the world. Gaia, the mother of us all. 

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Some images. None of them refers to a specific description in the text of this post, but they can give us some idea of what our ancestresses may have been looking like. 

This woman lived in Tuscany probably during the 2nd century BC, more than 2000 years ago. We know her name, "Larthia Seianti." She was Etruscan, a rich woman (note the armilla bracelet on her arm) who could afford an elaborate sculpture over her sarcophagus. It is a realistic portrait, at least in part. And, curiously, she looks a lot like a Tuscan friend of mine, living in Tuscany nowadays. She is likely one of her ancestress, just as an ancestress of mine. 

The reconstruction of the face of a Neolithic woman who lived about 7,500 years ago in the area that is now called Gibraltar. She has been nicknamed "Calpeia" from the ancient name of the Gibraltar mountain, "Mons Calpe." DNA analysis shows that she, or her immediate ancestors, came to the Iberian Peninsula most likely from Anatolia by boat. (source)

The "Venus of Brassenpouy," discovered in 1894 in Southern France. It is a  portrait of someone who lived more than 20,000 years ago. We cannot say whether it is realistic or not, just as we cannot be completely sure that it is a woman's face. But it is perhaps the earliest recognizable portrait ever made in human history.  

An impression of how a Paleolithic woman could have looked like, living maybe 20,000-50,000 years ago in Europe. Note her dark skin: it is a remnant of her African ancestry. (source)

 

A reconstruction of the face of a Neanderthal woman (from Earth Archives). She might have lived a few hundred thousand years ago. Several things in this image are uncertain, but note her heavy brow ridges, a typical Neanderthal characteristic. Note her eyes and her skin: the light color is a characteristic of people living in Northern regions. Is she an ancestor of some of us? It is not completely certain but, yes, many of us have Neanderthal genes in their DNA.

The reconstruction of a female Australopithecus who could have been living in Africa some 2 million years ago. If she had the typical human metabolism, she must have been capable of cooling by sweating. It is a feature incompatible with a thick body hair. And, indeed, she is shown with sparse hair, although she may well have had none. Note also her human-like round breasts. It is a likely secondary sexual characteristics of hominins which tend to stand upright most of the time. An ancestress of ours? Maybe. (source)

 

  

Societal Holobionts: An Introduction to the Concept

 

God must be incredibly fond of holobionts, since He created so many of them. And He (or She) may be a holobiont as well. 

 

It once happened, that the other members of a man mutinied against the stomach, which they accused as the only idle, uncontributing part the whole body, while the rest were put to hardships and the expense of much labour to supply and minister to its appetites. The stomach, however, merely ridiculed the silliness of the members, who appeared not to be aware that the stomach certainly does receive the general nourishment, but only to return it again, and redistribute it amongst the rest. (Plutarch, “Life of Coriolanus”)

In guerrilla warfare, select the tactic of seeming to come from the east and attacking from the west; avoid the solid, attack the hollow; attack; withdraw; deliver a lightning blow, seek a lightning decision. When guerrillas engage a stronger enemy, they withdraw when he advances; harass him when he stops; strike him when he is weary; pursue him when he withdraws. In guerilla strategy, the enemy's rear, flanks, and other vulnerable spots are his vital points, and there he must be harassed, attacked, dispersed, exhausted and annihilated. (Mao Zedong, 1937)

 

Maybe it happened to you to spend hours waiting for a flight in a busy international airport. You are blocked there and, after having had enough coffee to make you walk like a shuffle dancer, you have nothing else to do but to wander aimlessly from one shop to another. Bookstores offer something to read but, perhaps more interestingly, they give you a chance to get hints of what other people read. A rare chance of a glimpse of other people’s minds in our busy world.

So, what are people reading, nowadays? A lot of magazines and books that you can find in an airport bookstore are about the two primeval human interests: food and sex (the latter usually not so explicitly presented as the former). Apart from that, you find plenty of material on everyday matters: cellphones and other electronic gadgetry, cars, travel, religion, and more. In addition, the typical international airport bookstore has a section on how to deal with other people. They are self-help books that claim to train you on how to manage your relationship with your coworkers, your friends, and your family.

Evidently, many people find that dealing with others is a difficult matter, enough that they need help and guidance. It is a little strange, because we are all the result of at least three hundred thousand years of evolution of the species called homo sapiens. Our ancestors survived because they were good enough at creating and keeping relationships with their neighbors that would help them in times of need. But, perhaps, living in the modern society, so bewilderingly complicated, is more difficult than living in a tribe of hunters and gatherers.

Are these books really useful? There are good reasons to be skeptical. The books often seem to be a mishmash of this and that, they are not quantitative, not based on solid theories, not related to experimental evidence. The latest fad in management theory is a book titled “Reinventing Organizations.” The title may be interesting, but the substance of the book may be criticized. According to the author, good management has something to do with a hierarchy of colors. Infrared is primitive and bad, while the shade of blue called “teal.” is modern and good. Why that should be the case, is not explained anywhere in the book. That doesn’t mean to disparage a book that may have good points, but maybe you will agree with us that such a classification is a little arbitrary, to say the least.

So, can we make some order in this chaos? Maybe yes. And we can try to do that using the concepts of “holobiont” and the related one of “empathy.” The idea is that human societies of all kinds are the result of evolutionary pressure and that those you find in our world exist because there is a reason for them to exist. Just as biological holobionts are a feature of the biosphere, there exist societal holobionts, a feature of the human social sphere. Societal holobionts are an example of “Complex Adaptive Systems,” (CAS) that is, systems that develop a condition of stability called “homeostasis” and that tend to maintain it when perturbed. These holobionts are virtual, unlike the microbes in your gut. So, we may also call them “virtual holobionts.”

Let’s start with an example. The simplest kind of human organization is the least organized one: the crowd (you can also call it a “mob” or a “band”). It has no leaders, no hierarchy, no specializations. Yet, you recognize a crowd when you see one. Perhaps the first time when crowds were dealt with as something worth of interest was with the book by the French author Gustave le Bon “Psychologie des Foules, (1895) that was translated into English as « The Crowd, A study of the Popular Mind. ». Reading it today, you would probably judge it to be a poorly made political pamphlet. And, indeed, it had a certain success with right wing politicians. Nevertheless, it was one of the first studies of complex systems in sociology.

Crowds are not just a feature of human society; equivalents exist with many animal societies. They go with different names: storms (or flocks) of birds, schools of fish, herds of sheep, prides of lions, and there are other examples (for instance, a bacterial mat). In any case, they share the same characteristics: they are loosely bonded groups of individuals who may stay together for a while and dissociate back into single units at any time. But, as long as they exist, crowds (just like all human organizations) are groups of people linked together.

Let’s go deeper into the matter. If a crowd is an organization, albeit the simplest possible one, it could be described using those “organizational charts” that purport to describe how a company is organized. These charts are maps designed to describe the hierarchical territory of the company. They have also been used to describe the organization of entities such as the Sicilian Mafia and Drug Cartels. They can also map the relationships in a band of Chimps or Bonobos.

But an organizational chart can be much more than simply a static map that tells you whom you should see, for instance, to organize a shipment or to order a supply of something (or, if you are a male bonobo, where to find an available female). The chart tells us a lot on how the organization works and also something about how it developed over time. It is part of the field called “management science.”

A good way to interpret organizational charts is to see them as networks.  Network science is a relatively recent development that derives from a field called “graph theory.” It is something that deals with how points in space (called “vertices”, plural of “vertex”) are arranged in space in terms of pairwise links with other vertices. You see an example of a graph in the figure

 

You note that there are 6 vertices (also called “nodes”), each one connected to its nearest neighbors. In this case, the connections (“links” or “edges”) are not directional, but that may be explicit in some kinds of graphs. It may also be possible that a node is connected to several other nodes.

Graph theory is a branch of pure mathematics, and it deals only with geometric arrangements. Instead, “Network theory” (or “network science”) deals with applications of graph theory to the real world. In this case, the nodes are real entities: people, departments, servers, combat units, and much more. Also, the links are related to real methods of information exchange: documents, orders, radio signals, fiber optics, and more.

Armed with this a basic knowledge, let’s go back to the example of the crowd. The simplest crowd network we may imagine is one formed of just three people (or bonobos). Here is the graph.

You see that each node (one member of the group) is connected to his/her neighbors. Information flows from each node to the closest one. There is no hierarchy: all the nodes are the same, which is one of the characteristics of crowds/bands/flocks, etc. You can say that the relationship between the elements of this crowd is horizontal, as opposed to the vertical kind seen in hierarchical organizations such as companies, armies, etc, as we’ll see later on.

We can expand the graph to describe a system where there are more than three nodes. You see below several possible arrangements

 

In the first case (a), each node is connected only to its two nearest neighbors. It is a little like being squeezed in the crowd in a busy subway station – if you have ever visited Tokyo, you know what that means. In such a condition, you can only move together with the crowd, and you don’t see anything more than your nearest neighbors.

Things may be more complicated than that and, in the other images, you see how nodes may be connected to more nodes than just their near neighbors. In case (b) each node is in contact with 4 neighbors. It is still a crowd, but not so dense as case (a). Case (c) shows the possibility of long-range connections for some of the nodes. Maybe someone in the crowd is in contact with a friend in the same crowd, but using a cell phone. Case (d) refers to a kind of network that is called “fully connected,” meaning that every node is connected to every other node. In the real world, it is a rare occurrence, even though it may exist for very small networks. For instance, the 3-nodes example seen before is a fully connected network. All these arrangements are non-hierarchical, or “horizontal”.

All these examples are special cases where all nodes are not only identical, but have all the same number of connections. In most cases, this is not true and each element is connected to a different number of nodes.

The figure illustrates the variations in the number of connections. The left examples shows a network where every node has 4 links. The central one is called the “small world” network. Most connections are to the close neighbors, but some are long range. The right one has more links, randomly arranged, but it is not fully connected.

The reason why the central diagram is called “small world” deserves some explanation. It has to do with the distance (in terms of number of links) between nodes. In this kind of network, it grows proportionally to the logarithm of the number of nodes, so it is not as large as it would be if you had to crawl every node, one after the other, to reach a node on the other side of the circle. In a small world network, if you wanted to contact, say, the president of the United States, it is said that you need to go through no more than six steps, starting with a person you are in contact with. It is not exactly like this, but it is a long story. Let’s just say that it is a “natural” way in which networks tend to arrange themselves.

You may say that the number of connections provide an embryonic form of hierarchy in these networks. If knowledge is power, then more connections mean more knowledge and therefore more power. This hierarchical relationship is especially evident on the Internet. A site such as, say, the CNN is defined by an URL (Uniform Resource Locator) just like any other blog or site on the web. But the CNN has a hugely larger number of connections than the average web site and there is no doubt that it has much more power in terms of pushing memes in the memesphere. But, overall, these systems remain horizontal in the sense that CNN doesn’t have the possibility to order to bloggers what to publish or not to publish in their sites (so far). Many internet “bubbles” are relatively egalitarian, although some nodes (people or groups) carry more weight than others.

These non-hierarchical networks are the general representation of the concept of “holobiont.” The way Lynn Margulis described holobionts was in terms of a group of individuals of different species that moved together in the condition called “symbiosis,” a mutual relationship that provides advantages to all the creatures engaged in it. Holobionts imply an intricate network of relationships among the various member of the community, but no fixed hierarchical structure although, obviously, some members have more prestige and power than others. Margulis was thinking of microbial communities, but we can enlarge the definition to ensembles of animals (if you prefer the formal term, we could say “ensembles of metazoa”). But the organizational diagrams in the form of circles could describe them nicely.

But what is the advantage for an individual to be part of a crowd? (or a flock, or a herd, or a pride?). Are these individuals in a symbiotic relationship? Yes, they are, by all means. Symbiosis is a condition of mutual help that in systems is generated by the way the system is organized, NOT by the good will of the individuals (it would be hard to speak of good will among bacteria, for instance). The beauty of symbiosis is that all the creatures engaged in it strive for their own benefit but, in the process, they manage to benefit every other creature.

Said in this form, it sounds as an extreme version of Adam Smith’s “invisible hand,” still today the basis of liberalism as a political ideology. The idea of the invisible hand has been much ridiculed over the years (you know how many economists it takes to replace a light bulb? None, it is done by the invisible hand!). But the idea is good if it is applied with a grain of salt.

Ugo Bardi (yours truly) and his coworker Ilaria Perissi discussed this issue in a paper that they titled “The Sixth Law of Stupidity,” where we argued that the opposite of stupidity is when human beings enter in a condition of symbiosis with other people. We also argued that stupidity is temporary while intelligence is long term, which means that people tend to learn from their mistakes. Even creatures not especially known for their large brains (say, bacteria) tend to learn from their mistakes – and those who don’t learn are eliminated by natural selection.

So, humans in a crowd are in a symbiotic relationship even though they may not recognize that. The crowd offers a certain refuge to its members. Maybe for humans it is not a general rule: when you are being shelled or shot, the worst possible idea would be to form a crowd that would attract the enemy fire. But, if you look at crowds in the animal kingdom, their utility is evident. Have you ever observed the behavior of a storm of birds? You may see them landing on a patch of grass to feed. If you get close, one of the birds may see you, be scared, and fly off. Immediately, the nearby birds will be alerted and fly off, too. In a moment, the whole storm will be flying away. In this case, the crowd (the storm) offers a danger-detection service that a single bird cannot have. 

More in general, a storm/flock/herd/crowd offers statistical protection. A predator is not interested in destroying the whole flock, only at capturing as many individuals as it needs. So, if the flock is large, the probability for an individual to be captured is low. Of course, humans tend to destroy even things they don’t need, but this is part of the 6^th law of stupidity .

We have now a definition of how a holobiont is structured according to the network theory. We may want to represent it as a triangle and, thinking about that, there could be a relation with the triangular symbol “the eye of God.”

And, indeed, a triangle can be seen as the icon for both a holobiont and God (or the Goddess Gaia). But let's not go into theology, this introduction should be enough to understand what a holobiont is. The next step is the concept of hierobiont, a network partly or completely structured in a hierarchical manner. But we'll see that in another post.