Gaia on the Move: the Rise of the Savanna Monkeys

This text had already been published as an appendix to a longer post on the evolution of forests. It is republished here as a stand-alone post on the role of humans in the evolution of the world's forests (link to the image above)

Primates are arboreal creatures that evolved in the warm environment of the Eocene forests. They used tree branches as a refuge, and they could adapt to various kinds of food. Modern primates do not shy from hunting other species, maybe even ancient primates did the same. From the viewpoint of these ancient primates, the shrinking of the area occupied by tropical forests that started with the "Grande Coupure," some 30 million years ago, was a disaster. They were not equipped to live in savannas: they were slow on the ground: an easy lunch for the powerful predators of the time. Primates also never colonized the northern taiga. Most likely, it was not because they couldn't live in cold environments (some modern monkeys can do that), but because they couldn't cross the "mammoth steppe" that separated the Tropical forests from the Northern forests. If some of them tried, the local carnivores made sure that they didn't succeed. So, "boreal monkeys" do not exist (actually, there is one, shown in the picture, but it is not exactly a monkey!).  

Eventually, monkeys were forced to move into the savanna. During the Pleistocene, about 4 million years ago, the Australopithecines appeared in Africa, (image source). We may call them the first "savanna monkeys." In parallel, perhaps a little later, another kind of savanna monkey, the baboon, also evolved in Africa. In the beginning, australopithecines and baboons were probably practicing similar living techniques, but in time they developed into very different species. The baboons still exist today as a rugged and adaptable species that, however, never developed the special characteristics of australopithecines that turned them into humans. The first creatures that we classify as belonging to the genus Homo, the homo habilis, appeared some 2.8 million years ago. They were also savanna dwellers. 

This branch of savanna monkeys won the game of survival by means of a series of evolutionary innovations. They increased their body size for better defense, they developed an erect stance to have a longer field of view, they super-charged their metabolism by getting rid of their body hair and using profuse sweating for cooling, they developed complex languages to create social groups for defense against predators, and they learned how to make stone tools adaptable to different situations. Finally, they developed a tool that no animal on Earth had mastered before: fire. Over a few hundred thousand years, they spread all over the world from their initial base in a small area of Central Africa. The savanna monkeys, now called "Homo sapiens," were a stunning evolutionary success. The consequences on the ecosystem were enormous.

First, the savanna monkeys exterminated most of the megafauna. The only large mammals that survived the onslaught were those living in Africa, perhaps because they evolved together with the australopithecines and developed specific defense techniques. For instance, the large ears of the African elephant are a cooling system destined to make elephants able to cope with the incredible stamina of human hunters. But in Eurasia, North America, and Australia, the arrival of the newcomers was so fast and so unexpected that most of the large animals were wiped out. 

By eliminating the megaherbivores, the monkeys had, theoretically, given a hand to the competitors of grass, forests, which now had an easier time encroaching on grassland without seeing their saplings trampled. But the savanna monkeys had also taken the role of megaherbivores. They used fires with great efficiency to clear forests to make space for the game they hunted. Later, as they developed metallurgy, the monkeys were able to cut down entire forests to make space for the cultivation of the grass species that they had domesticated meanwhile: wheat, rice, maize, oath, and many others. 

But the savanna monkeys were not necessarily enemies of the forests. In parallel to agriculture, they also managed entire forests as food sources. The story of the chestnut forests of North America is nearly forgotten today but, about one century ago, the forests of the region were largely formed of chestnut trees planted by Native Americans as a source of food (image source). By the start of the 20th century, the chestnut forest was devastated by the "chestnut blight," a fungal disease that came from China. It is said that some 3-4 billion chestnut trees were destroyed and, now, the chestnut forest doesn't exist anymore. The American chestnut forest is not the only example of a forest managed, or even created, by humans. Even the Amazon rainforest, sometimes considered an example of a "natural" forest, shows evidence of having been managed by the Amazonian Natives in the past as a source of food and other products. 

The action of the savanna monkeys was always massive and, in most cases, it ended in disaster. Even the oceans were not safe from the monkeys: they nearly managed to exterminate the baleen whales, turning large areas of the oceans into deserts. On land, entire forests were razed to the ground. Desertification ensued, brought upon by "megadroughts" when the rain cycle was no more controlled by the forests. Even when the monkeys spared a forest, they often turned it into a monoculture, subjected to be destroyed by pests, as the case of the American chestnuts shows. Yet, in a certain sense, the monkeys were making a favor to forests. Despite the huge losses to saws and hatchets, they never succeeded in completely exterminating a tree species, although some are critically endangered nowadays. 

The most important action of the monkeys was their habit of burning sedimented carbon species that had been removed from the ecosphere long before. The monkeys call these carbon species "fossil fuels" and they have been going on an incredible burning bonanza using the energy stored in this ancient carbon without the need of going through the need of the slow and laborious photosynthesis process. In so doing, they raised the concentration of CO2 in the atmosphere to levels that had not been seen for tens of millions of years before. That was welcome food for the trees, which are now rebounding from their former distressful situation during the Pleistocene, reconquering some of the lands they had lost to grass. In the North of Eurasia, the Taiga is expanding and gradually eliminating the old mammoth steppe. Areas that today are deserts are likely to become green. We are already seeing the trend in the Sahara desert. 

What the savanna monkeys could do was probably a surprise for Gaia herself, who must be now scratching her head and wondering what has happened to her beloved Earth. And what's going to happen, now?  There are several possibilities, including a cataclysmic extinction of most vertebrates, or perhaps all of them. Or, perhaps, a new burst of evolution could replace them with completely new life forms. What we can say is that evolution is turbo-charged in this phase of the existence of planet Earth. Changes will be many and very rapid. Not necessarily pleasant for the existing species but, as always, Gaia knows best. 

Can HolobiontsThink?

 

My wife, a holobiont called Grazia, hugs another holobiont, a Cupressus Sempervirens, in the hills near Florence, Italy

This is an excerpt from the chapter I am writing for a multi-author book 

I started this chapter by examining trees and forests as holobionts, then looking at human beings. Trees and humans are as alien to each other as we could possibly imagine. Humans are mobile creatures with an extravagantly powerful metabolism that makes them able to sustain protracted efforts longer than any other living animal. That turbo-charged metabolism is also used to maintain their large brains, of which they are very proud. They use their brains to control their muscles and their sophisticated sensory apparatus, as well as to deal with each other in complicated social rituals.

Trees are the opposite in almost all respects: they are immobile, their metabolism is slow: and they can’t even control their internal temperature. They don’t have eyes, nerves, brains, and not even muscles. Yet, they move, they sense their environment mainly by chemical signals, but also visual and mechanical ones -- including vibrations in the acoustic frequency. They "know" what's going on around them, but in ways that are mostly alien to mobile mammals, including humans.

Nevertheless, humans and trees are both holobionts at their core, and they share more than it would seem at first sight. It is not even forbidden to ask whether trees and other plants might be “conscious” in some way. This is a subject of wide debate, nowadays, and it would be out of the scope of the present text to enter into the details of a question whose answer depends primarily on the definition of the entity being debated. For what we are concerned, we can rather ask the question of whether some creatures store somewhere a schematic representation of at least some elements of the outside world, and modify their behavior depending on the sensor input they receive. That implies a certain level of “consciousness.”

In the case of human beings, there is no doubt that this capability exists. Assuming that most of the readers of this text are human, they should be familiar with the typical sensation of being encased in a bodily container. We have no direct perception of having a brain, but somehow we perceive that we are “inside” a body, that we are a sort of "homunculus" that resides someplace behind the eyes. And, surely, we do keep representations of the outside world, sometimes even too much, as when our political leaders claim that they can “create their own reality.”

How about a tree, then? Where would a tree have its representation of the outside world? As I said, trees have no brains and no nervous system, but they can transmit electric signals from cell to cell. It is a still scarcely known field, but it is known that the phloem and xylem cells form a network to transmit electrical signals long-distance within the plant. At the root level, the mycorrhizal system shares chemical signals within single plants and also from one plant to another. Would such a network be able also of storing information, just like a neural network does in animals? There is no reason to deny that it could. In this case, the representation of the outside world would be stored in the plant as a configuration of the network, continuously changed by sensorial inputs, and leading to signals being transmitted to the various parts of the plants instructing them, for instance, to release volatile organic compounds to fight an insect attack.

If that were the case, apart from the slippery concept of consciousness, a plant would not have the sensation of being encased in a bone cage that humans have. Its intelligence would be delocalized all over the structure. The plant would “feel” the conditions of the leaves, and the presence of sunlight. It would “smell” chemicals floating in the air and perceive the sound of living creatures moving in the vicinity. It would also be actively sending and receiving chemical signals through the mycorrhizal system. In short, it might have a representation of the external world of complexity comparable to the one that humans can build in from their sensorial input. Whether plants could also “create their own reality,” that is, dream, is impossible to say. Communicating with trees is a challenge that was never met, at least in terms compatible with the scientific method. Nevertheless, there seems to be a certain empathy between trees and humans. In the photo, the author’s wife, Grazia, communicates with a specimen of Cupressus sempervirens, in Tuscany.

About this encounter of these two holobionts, we may speculate about their reciprocal sensorial experience. For the human, the tree holobiont is perceived mainly as a visual entity -- but her sensorial system has no capability of detecting the underground root system. Nor she can detect the complex chemical signaling that the tree is operating inside and outside itself. For the tree, instead, the human cannot generate as a visual image, but it is possible that the tree perceives the human from the vibrations she generates and, maybe, detecting the chemical signals she produces. Whether the tree knows that it is being hugged is impossible to say, but we cannot completely discount this possibility. As a further note, both humans and trees use sunlight for chemical processing on their surfaces. Trees use it for photosynthesis, while humans need it to synthesize the compound called "Vitamin D" that they need for their survival.   

We can gather from this discussion that creating a representation of the outside world is a fundamental survival element of holobionts. And since holobionts are the main form that life on Earth takes, we should admit that all holobionts have this kind of capability. In other words, holobionts can “think.” Not in the same way as humans think, of course. But the process of thinking is part of the homeostatic adaptation that all living beings tend to attain. To accomplish that, they need to process information: it is the basic idea of the “dissipation structures” as defined by Prigogine. These structures process entropy and dissipate it, and entropy is basically information. So, holobionts are structured in such a way as to modify their internal structure to obtain homeostasis and maintain it despite changes in the structure of their environment. The holobiont itself is the holobiont’s “brain” and its internal structure stores a representation of the outside world.

Seen in these terms, the hypertrophic brain of which humans are so proud is not an exception to the rule that holobionts store information in their networked structure. All the neurons in the human brain are the same: there is no “super-neuron” that controls the other neurons. In a sense, you could say that the brain is a holobiont, possibly the biggest one known in the ecosystem in terms of the units it contains, with a total of some 86 billion neurons. It is still a small number if compared to the genetic information stored by the whole biosphere has been estimated as Thus, the total amount of genetic information stored in the natural biota is of the order of 1016 bit (Gorshkov et al., 2000) and coincides as an order of magnitude with the information stored in a human brain. This similarity may give us some interesting insights about the idea that the world in which we live is a single, extremely large, holobiont to which we sometimes give the name of Gaia, the Earth Goddess (Castell et al., 2019)

This Planet Needs us, Just as we Need this Planet

 

The baroque music of Jean-Philippe Rameau coupled with modern street dance. The result is nearly mind-boggling. Gaia appears to us in her vital, strong, exuberant form.

To be sure, it would be difficult to say that Rameau was an ecologist. This opera, "Les Indes Galantes" was composed in 1736 and the views of the time were very different from ours and the story is weak, a sugary pastiche of exotic loves, not truly very interesting. But Rameau was first and foremost a composer, a great innovator in his times. And, here, the music he proposes to us sounds very modern in how it catches the strong armonies of the natural world. What's most remarkable is how some people in the early 18th century already saw forests as a source of life and peace.  The main words say,

Pleasant Forests, pleasant forests

Heaven, heaven, you made them

For innocence and for peace

 

After that Luisella Chiavenuto sent me a link to this piece, I have seen it, I think, 20 times, maybe more. And every time I watch it, it seems to me mind-boggling that in 1736 someone could compose a music that would match so well and so perfectly with our modern street dancing. The intensity of the whole scene... it is indescribable. Look at the faces of the dancers, look at the singer, Sabine Dievilhe, look at how intensely she sings, she acts, she moves. You have to feel in your guts, you cannot perceive it with your brain. 

 

Perhaps the most surprising thing is that this moment of incredible intensity comes from a opera that's little more than a sugary story that reflect plenty of prejudice against the "savages" that Europeans encountered in their saga of domination of the lands beyond the oceans.

 

Yet, Rameau manages to convey the feeling they must have had at that time, the discovery that the world was so much larger than it had been thought to be not long before. A world that, in our times, has shrunk to nearly nothing, encroached by the human expansion that has destroyed nearly everything that at the time of Rameau could be called "savage."

 

So, today, like at the time of Rameau, we lounge for something that maybe exists/existed only in our dreams. But dreams are not a matter of little importance. They have a remarkable tendency to tell us much more than we can perceive when awake. And the dream of the "pleasant forests" that Rameau thought and that Sabine Dievilhe sings so well remains with us.

 

Humans are not just wood-cutting animals. When they are at their best, they can do this and even more beautiful things, all part of the infinite variety of Gaia. 

 

 

h/t

Luisella Chiavenuto