Thinking like a Tree. Old-Growth Forests as Holobionts

A "holobiont" is a living creature formed of independent, but cooperating, organisms. It is a wide-ranging concept that can explain many things not just about the ecosystem of our planet, but also about human society, and even more than that. Photo courtesy of Chuck Pezeshky. This post was modified and improved thanks to suggestions received from Anastassia Makarieva.

When was the last time that you walked through an old-growth forest? Do you remember the silence, the stillness of the air, the sensation of awe, the feeling that you are walking in a sacred place? The inside of a forest looks like a cathedral or, perhaps, it is the inside of a cathedral that is built in such a way to resemble a forest, with columns as trees and vaults as the canopy.  If you don't have a forest or a cathedral nearby, you can get the same feeling by watching the masterful scene of the forest-God appearing in Miyazaki's movie, "Mononoke no Hime" (The Princess of the Ghosts). 

In a way, when you walk among trees, you feel that you are at home, the home that our remote ancestors left to embark on the mad adventure of becoming human. Yet, for some humans, trees have become enemies to be fought. And, as it is traditional in all wars, they are demonized and despised. It was the English landlord Jonah Barrington who commented about the destruction of Ireland's old forests that "trees are stumps provided by Nature for the repayment of debt." And, as it is traditional in all wars of extermination, not a single enemy was left standing. 

The war metaphor is engrained in our minds of primates, the only mammals that wage war against groups of their own species. So much that sometimes we imagine trees fighting back. In the "Trilogy of the Ring" by Tolkien, we see walking trees, the "ents," standing in arms against humanoid enemies and defeating them. Clearly, we feel guilty for what we have been doing to Earth's forests. A sensation of guilt that goes back to the time when the Sumerian King Gilgamesh and his friend Enkidu were cursed by the Goddess for having destroyed the sacred trees and killed their guardian, Humbaba. From that remote time, we have continued to destroy Earth's forests, and we are still doing that. 

Yet, if there is a war between trees and humans, it is not obvious that humans will win it. Trees are complex, structured, adaptable, tough, and resourceful creatures. Despite the human attempts to destroy them, they survive and even thrive. The most recent data indicate a greening trend of the whole planet [3], probably the result of humans pumping carbon dioxide (CO2) into the atmosphere (this greening is not necessarily a good thing, neither for trees nor for humans [4], [5]). 

But what are trees, exactly? They have no nervous system, no blood, no muscles, just as we have no capability of doing photosynthesis, nor of extracting minerals from the soil. Trees are truly alien creatures, yet they are made of the same building blocks as we are: their cells contain DNA and RNA molecules, their metabolism is based on the reduction of a molecule called adenosine triphosphate (ATP) created by mitochondria inside their cells, and much more. And, in a certain sense, trees do have a brain. The root system of a forest is a network similar to that of a human brain. It has been termed the “Wood-Wide Web” by Suzanne Simard and others [1]. What trees “think” is a difficult question for us, monkeys but, paraphrasing Sir. Thomas Browne [2], what trees are thinking, just like what song the Sirens sang to Ulysses, though puzzling questions are not beyond all conjecture. 

Whether trees think or not, they have the basic characteristics of all complex living systems: they are holobionts. "Holobiont" is a concept popularized by Lynn Margulis as the basic building block of the ecosphere. Holobionts are groups of creatures that collaborate with each other while maintaining their individual characteristics. If you are reading this text, you are probably a human being and, as such, you are also a holobiont. Your body hosts a wide variety of creatures, mostly bacteria, that help you in various tasks, for instance in digesting food. A forest is another kind of holobiont, vaster but also structured in terms of collaborating creatures. Trees could not exist alone, they need the all-important "mycorrhizal symbiosis." It has to do with the presence of fungi in the soil that collaborate with plant roots to create an entity called the “rhizosphere,” the holobiont that makes it possible for a forest to exist. Fungi process the minerals that exist in the soil and turn them into forms that plants can absorb. The plant, in turn, provides the fungi with energy in the form of sugars obtained from photosynthesis. 

So, even though trees are familiar creatures, it is surprising how many things are scarcely known about them and some are not known at all. So, let’s go through a few questions that disclose whole new worlds in front of us. 

First: wood. Everyone knows that trees are made of wood, of course, but why? Of course, its purpose is the mechanical support of the whole plant. But it is not a trivial question. If wood serves for mechanical support, why aren’t our bones made of wood? And why aren’t trees, instead, made of the stuff our bones are made of, mainly solid phosphate?

As usual, if something exists, there is some reason for it to exist. Within some limits, evolution may take different paths simply because it has started moving in a certain direction and it cannot move back. But, as things stand on Earth, wooden trunks are perfectly optimized for their purpose of support of a creature that doesn't move. Tree trunks (not palms, though) grow in concentric layers: it is well known that you can date a tree by counting the growth rings in its trunk. As a new layer grows, the inside layers die. They become just a support for the external layer called the “cambium” which is the living part of the trunk, containing the all-important “xylem”, the ducts that bring water and nutrients from the roots to the leaves. The cambium also contains the "phloem," another set of ducts that move water loaded with sugars in the opposite direction, toward the roots. The inner part of the trunk is dead, so it has no metabolic cost for the tree. Yet, it keeps providing the static support the tree needs. 

The disadvantage is that, because the internal part of the wood is dead, when a branch or a trunk is broken, it cannot be healed by reconnecting the two parts together. In animals, instead, the bones are alive: there is blood flowing through them. So, they can regrow and rebuild the damaged parts. It is probably a necessary feature for animals. They jump, run, fly, fall, roll, and do more acrobatic feats, often resulting in broken bones. Of course, a broken bone is a major danger, especially for a large animal. We don’t know exactly how many animals suffer broken bones and survive, but it seems that it is not uncommon: live bones are a crucial survival feature [6], [7]. But that's not so important for trees: they do not move and the main stress they face is a heavy gust of wind. But trees tend to protect themselves from wind by shouldering against each other – which is, by the way, another typical holobiont characteristic: trees help each other resisting wind, but not because they are ordered to do so by a master tree. It is just the way they are.

That's not just the only feature that makes wood good for trees but not for animals. Another one is that bones, being alive, can grow with the creature they support. They can even be hollow, as in birds, and so be light and resilient at the same time. If our bones were made of wood, we would have to carry around a large weight of deadwood in the inner part of the bone. That's not a problem for trees which, instead, profit from a heavier weight in terms of better stability. And they do not have to run unless they are the fantasy creatures called "ents."  Spectacular, but Tolkien would need to perform some acrobatic feats of biophysics to explain how some trees of Middle Earth can walk around as fast as humans do.

So, there is plenty of logic in the fact that trees use wood as a structural material. They are not the only creatures doing that. Bamboos (bambusoideae), are also wooden, but they are not trees. They are a form of grass that appeared on Earth just about 30 million years ago, when they developed an evolutionary innovation that makes their "trunk” lighter, being hollow. So, they can take much more stress than trees before breaking and that inspired many Oriental philosophers about the advantages of bending without breaking. Among animals, insects and arthropods use a structural material similar to wood, called "chitin." They didn't solve the problem of how to make it grow with the whole organism, so use it as an exoskeleton that they need to replace as they grow.

Now, let's go to another question about trees. How does their metabolism work? You know that trees create their own food, carbohydrates (sugar), by photosynthesis, a process powered by solar light that works by combining water and carbon dioxide molecules. One problem is that sunlight arrives from above, whereas trees extract water from the ground. So, how do they manage to pump water all the way to the leaves? 

We animals are familiar with the way water (actually, blood) is pumped inside our bodies. It is done by an organ called "heart," basically a "positive displacement pump" powered by muscles. Hearts are wonderful machines, but expensive in terms of the energy they need and, unfortunately, prone to failure as we age. But trees, as we all know, have no muscles and no moving parts. There is no “heart” anywhere inside a tree. It is because only the feverish metabolism of animals can afford to use so much energy as it is used in hearts. Trees are slower and smarter (and they live much longer than primates). They use very little energy to pump water by exploiting capillary forces and small pressure differences in their environment. 

"Capillary forces" means exploiting interface forces that appear when water flows through narrow ducts. You exploit that every time you use a paper towel to soak spilled water. It doesn't happen in human-made ducts, nor in the large blood vessels of an animal body. But it is a fundamental feature in the movement of fluids in heartless (not in the bad sense of the term) plants. But capillary forces are not enough, by far. You need also a pressure difference to pull the water high enough to reach the canopy. That you can attain by evaporating water at the surface of leaves. The water that goes away as water vapor creates a small difference in pressure that can pull more water up from below. This is called a "suction pump." You experience it every time you use a straw to drink from a glass. It is, actually, the atmospheric pressure that pushes the water up the straw. 

Now, there is a big problem with suction pumps. If you studied elementary physics in school, you learned that you cannot use a suction pump to pull water higher than about 10 meters because the weight of the water column cannot exceed the atmospheric push. In other words, you wouldn't be able to drink your coke using a straw longer than 10 meters. You probably never made the experiment, but now you know that it won't work! But trees are far higher than ten meters. You just need to visit your local park to find trees that are far taller than that. 

That trees can grow so tall is a little miracle that even today we are not sure we completely understand. The generally accepted theory for how water can be pumped to such heights is called the “cohesion-tension theory” [8].  In short, water behaves, within some limits, as a solid in the live part of a tree trunk, the “xylem.” The ducts do not contain any air and water is pulled up by a mechanism that involves each molecule pulling all the nearby molecules. The story is complicated and not everything is known about it. The point is that trees do manage to pump water to heights up to about 100 meters and even more. There is a redwood tree (Sequoia sempervirens), in California, that reaches a height of 380 feet, (116 m). It is such an exceptional tree, that it has a specific name “Hyperion.” 

Could trees grow even higher? Apparently not, at least not on this planet. We are not sure of what is the main limiting factor. Possibly, the cohesion-tension pumping mechanism that brings water to the leaves ceases to work over a certain height. Or it could be the opposite problem: the phloem becoming unable to carry sugar all the way down to the roots. Or, perhaps, there are mechanical limits to the trunk size that can support a crown large enough to feed the whole tree. 

Nevertheless, some works of fiction imagined trees so huge that humans could build entire cities inside or around the trunk. The first may have been Edgar Rice Burroughs, known for his "Tarzan" novels. In a series set on the planet Venus, in 1932, he imagined trees so big that an entire civilization had taken refuge in them. Just a couple of years later, Alex Raymond created the character of Prince Barin of Arboria for his "Flash Gordon" series. Arboria, as the name says, is a forested region and, again, trees are so big that people can live in them. More recently, you may remember the gigantic "Hometrees" of the Na'vi people of planet Pandora in the movie "Avatar" (2009).  In the real world, some people do build their homes on trees -- it seems to be popular in California. The living quarters must be cramped, to say nothing about the problems with the static stability of the whole contraption. But, apparently, a section of our fantasy sphere still dreams about the times when our remote ancestors were living on trees. 

But why do trees go to such an effort to become tall? If the idea is to collect solar light, which is the business all plants are engaged in, there is just as much of it at the ground level as there is at 100 meters of height. Richard Dawkins was perplexed about this point in his book “The Greatest Show on Earth” (2009), where he said:

“Look at a single tall tree standing proud in the middle of an open area. Why is it so tall? Not to be closer to the sun! That long trunk could be shortened until the crown of the tree was splayed out over the ground, with no loss in photons and huge savings in cost. So why go to all that expense of pushing the crown of the tree up towards the sky? The answer eludes us until we realize that the natural habitat of such a tree is a forest. Trees are tall to overtop rival trees - of the same and other species. … A familiar example is a suggested agreement to sit, rather than stand, when watching a spectacle such as a horse race. If everybody sat, tall people would still get a better view than short people, just as they would if everybody stood, but with the advantage that sitting is more comfortable for everybody. The problems start when one short person sitting behind a tall person stands, to get a better view. Immediately, the person sitting behind him stands, in order to see anything at all. A wave of standing sweeps around the field, until everybody is standing. In the end, everybody is worse off than they would be if they had all stayed sitting.”

Dawkins is a sharp thinker but sometimes he takes the wrong road. Here, he reasons like a primate, actually a male primate (not surprising, because it is what he is). The idea that trees “compete with rival trees – of the same and other species” just doesn’t work. Trees can be male and female, although in ways that primates would find weird, for instance with both male and female organs on the same plant. But male trees do not fight for female trees, as male primates do with female primates. A tree would have no advantage in killing its neighbors by shadowing them -- that wouldn't provide "him" or "her" with more food or more sexual partners. Killing the neighbors would perhaps allow a tree to grow a little larger, but, in exchange, it would be more exposed to the gust of wind that could topple it. In the real world, trees protect each other by staying together and avoiding the full impact of gusts of wind. 

It doesn’t always work and if the wind manages to topple a few trees, then a domino effect may ensue and a whole forest may be brought down. In 2018, some 14 million trees were destroyed in Northern Italy by strong gales. The disaster was probably the result of more than a single cause: global warming has created winds of a strength unknown in earlier times. But it is also true that most of the woods that were destroyed were monocultures of spruce, plantations designed for wood production. In the natural world, forests are not made of identical trees, spaced from each other like soldiers in a parade. They are a mix of different species, some taller, some less tall. The interaction among different tree species depends on a number of different factors and there is evidence of complementarity among different species of trees in a mixed forest [9], [10]. The availability of direct sunlight is not the only parameter that affects tree growth and mixed canopies seem to adapt better to variable conditions. 

As a further advantage of being tall, a thick canopy that stands high up protects the ground from sunlight and avoids the evaporation of moisture from the soil, conserving water for the trees. When the sun makes the canopy hotter than the soil, the result is that the air becomes hotter higher up, technically it is called "negative lapse rate" [11].  Since the cold air is below the hot air, convection is much reduced, the air stays still, and water remains in the soil. If that's not completely clear to you, try this experiment: on a hot day, scorching if possible, stand in the sun while wearing a thick wool winter hat for several minutes. Then wear a sombrero. Compare the effects. 

So, you see that having a canopy well separated from the ground is another collective effect generated by trees forming a forest. It doesn't help single trees so much, but it does help the forest in conserving water by generating something that we could call a "holobiont of shadows." Each tree helps the others by shadowing a fraction of the ground, below. And that creates, incidentally, the "cathedral effect" that we experience when we walk through a forest. Again, we see that this point was missed by Dawkins when he said that "That long trunk could be shortened until the crown of the tree was splayed out over the ground, with no loss in photons and huge savings in cost." Another confirmation of how difficult it is for primates to think like trees. 

That doesn’t mean that trees do not compete with other trees or other kinds of plants. They do, by all means. It is typical for a forest especially after an area has been damaged, for instance by fire. In that area, you see growing first the plants that grow faster, typically herbs. Then, they are replaced by shrubs, and finally by trees. The mechanism is generated by the shadowing of the shorter species created by the taller ones. It is a process called "recolonization" that may take decades, or even centuries before the burned patch becomes indistinguishable from the rest of the forest.

These are dynamic processes: fires are part and parcel of the ecosystem, not disasters. Some trees, such as the Australian eucalypti and the African palms seem to have evolved with the specific purpose of burning as fast as possible and spreading flames and sparks around. Have you noticed how palms are “hairy”? They are engineered in such a way to catch fire easily. So much, that it may be dangerous to prune a palm by using a chainsaw while climbing it. A spark from the engine may set on fire the dry wood filaments and that may be very bad for the person strapped to the trunk. It is not that palms could have evolved this feature to defend themselves from chainsaw-yielding monkeys, but they are fast-growing plants that may benefit from how a fire cleans a swat of ground, letting them re-colonize it faster than other species. Note how palms act like kamikaze: single plants sacrifice themselves for the survival of their seed. It is another feature of holobionts. Some primates do the same, but it is rare. 

Other kinds of trees adopt the opposite approach. They optimize their chances for survival when exposed to fire by means of thick bark. The ponderosa pine (Pinus ponderosa) is an example of a plant adopting this strategy. Then there are more tricks: have you ever wondered why some pinecones are so sticky and resinous? The idea is that the resin glues the cone to a branch or to the bark of the tree and keeps the seeds inside. If a fire burns the tree, the resin melts, and the seeds inside are left free to germinate. More evidence that fires are not a bug but a feature of the system. 

In the end, a forest, as we saw, is a typical holobiont. Holobionts do not evolve by the fight for survival that some interpretations of Darwin’s theory had imagined being the rule in the ecosystem. Holobionts can be ruthless when it is necessary to eliminate the unfit, but they aim at an amicable convivence of the creatures that are fit enough. 

The “holobiontic” characteristic of forests is best evidenced by the concept of “biotic pump,” an example of how organisms benefit the holobiont they are part of without the need for hierarchies and planning.



The concept of biotic pump [11] was proposed by Viktor Gorshkov, Anastassia Makarieva, and others, as part of the wider concept of biotic regulation [12]. It is a profound synthesis of how the ecosphere works: it emphasizes its regulating power that keeps the ecosystem from straying away from the conditions that make it possible for biological life to exist. From this work comes the idea that the ecosystemic imbalance we call "climate change" is caused only in part by CO2 emissions. Another important factor is the ongoing deforestation. This is, of course, a controversial position. The general opinion among climatologists in the West is that growing a forest has a cooling effect because it removes some CO2 from the atmosphere. But, once a forest has reached its stable state, it has a warming effect on Earth’s climate because its albedo (the light reflected back into space) is lower than that of the bare ground. But studies exist [13] that show how forests cool the Earth not only by sequestering carbon in the form of biomass but because of a biophysical effect related to evapotranspiration. That is, the water evaporates at low altitudes from the leaves, causing cooling. It returns the heat when it condenses in the form of clouds, but the heat emissions at high altitudes are more easily dispersed towards space because the main greenhouse gas, the water, exists in very small concentrations. It may be a minor effect compared to that of the albedo, but it is a point not very well quantified. 

The concept of biotic pump states that forests act as "planetary pumping systems," carrying water from the atmosphere above the oceans up to thousands of kilometers inland. It is the mechanism that generates the “atmospheric rivers” that supply water to lands that are far away from the seas [14]. The biotic pump mechanism depends on quantitative factors that are still little known. But it seems that the water transpired by trees condenses above the forest canopy and the phase transition from gas to liquid generates a pressure drop. This drop pulls air from the surroundings, all the way from the moist air over the sea. This mechanism is what allows the inner areas of the continents to receive sufficient rain to be forested. It doesn’t work everywhere, in Northern Africa, for instance, there are no forests that bring the water inland, and the result is the desert region we call the Sahara. But the biotic pump operates in Northern Eurasia, central Africa, India, Indonesia, Southern, and Northern America.

The concept of the biotic pump is an especially clear example of how holobionts operate. Single trees don’t evaporate water in the air because they somehow “know” that this evaporation will benefit other trees. They do that because they need to generate the pressure difference they need to pull water and nutrients from their roots. In a certain sense, evapotranspiration is an inefficient process because, from the viewpoint of an individual tree, a lot of water (maybe more than 95%) is "wasted" in the form of water vapor and not used for photosynthesis. But, from the viewpoint of a forest, the inefficiency of single trees is what generates the pull of humidity from the sea that makes it possible for the forest to survive. Without the biotic pump, the forest would quickly run out of water and die. It often happens with the rush to "plant trees to stop global warming" that well-intentioned humans are engaged in, nowadays. It may do more harm than good: to stabilize the climate, we do not need just trees, we need forests. 

Note another holobiontic characteristic of trees in forests: they store very little water, individually. They rely almost totally on the collective effect of biotic pumping for the water they need: that's because they are good holobionts! Not all trees are structured in this way. An example is the African baobab, which has a typical barrel-like trunk, where it stores water more or less in the same way as succulent plants (cacti) do. But baobabs are solitary trees, 

Incidentally, evapotranspiration is one of the few points that trees have in common with the primates called "homo sapiens." The sapiens, too, "evapotranspirate" a lot of water out of their skins -- it is called "sweating." But the metabolism of primates is completely different: trees are heterothermic, that is their temperature follows that of their environment. Primates, instead, are homeotherms and control their temperature by various mechanisms, including sweating. But that doesn't create a biotic pump! 

The concept of "biotic pump" generated by the forest holobiont is crucial the correlated one of "biotic regulation," [12] the idea that the whole ecosystem is tightly regulated by the organisms living in it. Natural selection worked at the holobiont level to favor those forests that operated most efficiently as biotic pumps. Plants other than trees and also animals do benefit from the water rivers generated by the forest even though they may not evotranspirate anything. They are other elements of the forest holobiont, an incredibly complex entity where not necessarily everything is optimized, but where, on the whole things move in concert. 

It is a story that we, monkeys, have difficulties in understanding: with the best of goodwill, it is hard for us to think like trees. Likely, the reverse is also true and the behavior of monkeys must be hard to understand for the brain-like network of the tree root system of the forest. It does not matter, we are all holobionts and part of the same holobiont. Eventually, the great land holobiont that we call “forests” merges into the greater planetary ecosystem that includes all the biomes, from the sea to land. It is the grand holobionts that we call “Gaia.” 

References

[1] S. W. Simard, D. A. Perry, M. D. Jones, D. D. Myrold, D. M. Durall, and R. Molina, “Net transfer of carbon between ectomycorrhizal tree species in the field,” Nature, vol. 388, no. 6642, pp. 579–582, Aug. 1997, doi: 10.1038/41557.

[2] T. Browne, “Hydriotaphia,” in Sir Thomas Browne’s works, volume 3 (1835), S. Wilkin, Ed. W. Pickering, 1835.

[3] Shilong Piao et al., “Characteristics, drivers and feedbacks of global greening,” | Nature Reviews Earth & Environment, vol. 1, pp. 14–27.

[4] D. Reay, Nitrogen and Climate Change: An Explosive Story. Palgrave Macmillan UK, 2015. doi: 10.1057/9781137286963.

[5] A. Sneed, “Ask the Experts: Does Rising CO2 Benefit Plants?,” Scientific American. https://www.scientificamerican.com/article/ask-the-experts-does-rising-co2-benefit-plants1/ (accessed Jun. 23, 2021).

[6] S. Hoffman, “Ape Fracture Patterns Show Higher Incidence in More Arboreal Species,” Discussions, vol. 8, no. 2, 2012, Accessed: Jun. 26, 2021. [Online]. Available: http://www.inquiriesjournal.com/articles/799/ape-fracture-patterns-show-higher-incidence-in-more-arboreal-species

[7] C. Bulstrode, J. King, and B. Roper, “What happens to wild animals with broken bones?,” Lancet, vol. 1, no. 8471, pp. 29–31, Jan. 1986, doi: 10.1016/s0140-6736(86)91905-7.

[8] Pi. Cruiziat, “Plant Physiology and Development, Sixth Edition,” in Plant Physiology and Development, Oxfprd University Press, 2006. Accessed: Jun. 24, 2021. [Online]. Available: http://6e.plantphys.net/essay04.03.html

[9] L. J. Williams, A. Paquette, J. Cavender-Bares, C. Messier, and P. B. Reich, “Spatial complementarity in tree crowns explains overyielding in species mixtures,” Nat Ecol Evol, vol. 1, no. 4, pp. 1–7, Mar. 2017, doi: 10.1038/s41559-016-0063.

[10] S. Kothari, R. A. Montgomery, and J. Cavender-Bares, “Physiological responses to light explain competition and facilitation in a tree diversity experiment,” Journal of Ecology, vol. 109, no. 5, pp. 2000–2018, 2021, doi: 10.1111/1365-2745.13637.

[11] Gorshkov, V.G and Makarieva, A.M., “Biotic pump of atmospheric moisture as driver of the hydrological cycle on land,” Hydrology and Earth System Sciences Discussions, vol. 3, pp. 2621–2673, 2006.

[12] V. G. Gorshkov, A. Mikhaĭlovna. Makarʹeva, and V. V. Gorshkov, Biotic regulation of the environment : key issue of global change. Springer-Verlag, 2000. Accessed: Sep. 24, 2017. [Online]. Available: http://www.springer.com/it/book/9781852331818

[13] R. Alkama and A. Cescatti, “Biophysical climate impacts of recent changes in global forest cover,” Science, vol. 351, no. 6273, pp. 600–604, Feb. 2016, doi: 10.1126/science.aac8083.

[14] F. Pearce, “A controversial Russian theory claims forests don’t just make rain—they make wind,” Science | AAAS, Jun. 18, 2020. https://www.sciencemag.org/news/2020/06/controversial-russian-theory-claims-forests-don-t-just-make-rain-they-make-wind (accessed Jun. 25, 2021).

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. 

_______________________________________________________________________

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)

 

  

Anastassia Makarieva: Biotic Regulation in Florence

 

Anastassia Makarieva  (center) receives a gift of appreciation for her talk in Florence, on Dec 11th, 2021, from Nicola and Anna in the form of a jewel made by Nicola, jeweler in Florence.

We had the pleasure of a visit to Florence of Anastassia Makarieva, one of the world's most creative and brilliant scientists in the field of ecosystems. Anastassia, together with Viktor Gorshkov, is the originator of the concepts of "biotic regulation" and "biotic pump" -- both fundamental in our understanding of the functioning of the ecosphere. Together, they mean that the current climate change is only in part the direct consequence of the increase in greenhouse gas emissions, but in significant part the result of the human perturbation of the ecosystem, and in particular the destruction of the old-growth forests. 

So, Anastassia carries a message: it is vital for the planet to keep forests alive and in their pristine state. And that means just what the word says: forests, not just trees. Those politicians who compete for who plants more trees are just doing greenwashing. They may be harming the planetary ecosystem more than helping it. A tree, alone or as part of a plantation, does not have the same balancing effect and water carrying system that a forest has. A message that's not easy to understand for the current generation of decision-makers, used to the concept that a tree is worth only what profit it can provide once it is cut and sold on the market. Nevertheless, we must try to pass this message. 

For Anastassia's talk in Florence, we experimented with a new format of presentation. To have Anastassia give an "official" talk, I should have gone through I don't even know what mass of paperwork, and then her talk would have been attended only by the few academics who still have some interest in creative research. All that in a super-safe, soulless room. The university, nowadays, has become something like Dracula's castle, with the difference that it is a scary place even in the daytime. 

To say that these official seminars can be disappointing is an understatement. A few years ago I organized a talk by a Russian scientist on the question of the supply of gas from Russia to Europe. You would think it is an interesting subject. Well, the attendees were exactly zero, besides me, the sponsor of the talk, and the Russian scientist herself. And at that time there was no Covid yet to make people afraid even of their shadows.   

So, this time we decided to play it differently: a colleague of mine kindly offered her living room to host Anastassia's seminar and we announced it on the social channels in addition to the regular university channels. We also offered drinks and snacks. We didn't know what to expect and we had no idea of how many people would bother taking a trip to the hills near Florence to listen to a Russian researcher speaking in English about her research. 

It was a remarkable success. Not a big crowd, but we collected about 25 persons, of whom only 3 were professional scientists (I think they were those who would have shown up had we organized the talk in the university). And they all listened with extreme interest to Anastassia's talk, fascinated by the story of how the ecosphere stabilizes climate and how the forest's biotic pump creates wind and rain. When it was the time of telling the story of how Anastassia and Viktor survived for months in the boreal forests in a tent, with bears strolling nearby, the audience was completely captivated. The informal party after the seminar was an occasion to build up friendship among people who share the same views of the world, even though they are not necessarily scientists.  

There is something to learn, here. Science is not a Moloch to worship, nor a dictator to be obeyed. And it is not even a conventicle of hyperspecialists who know so much about so little that they can be said to know everything about nothing. Science is one of the several possible embodiments of the concept of "philosophy," the love of knowledge. It is something that does not belong to anybody, it belongs to everybody. And that was clear at Anastassia's talk. 

h/t Benedetta Treves and all those who helped organize this seminar. To know more about the biotic pump and biotic regulation, see the site https://bioticregulation.ru/

Anastassia Makarieva on the role of forests in Earth's climate

 

If you can, do spend half an hour to watch the talk that Anastassia Makarieva gave at the Technical University of Munich (TUM) on 24.11.2021.

It is not easy stuff if you are not familiar with the field of atmospheric water circulation, but it is worth making the effort. Anastassia and her colleagues are doing nothing less than revolutionizing the way we understand the role of forests in the ecosystem. Rather than being a passive entity for humans to make chairs and cricket bats, forests may actually be what makes life on Earth possible, they are part of the great planetary holobiont that uses forests to regulate itself. 

The Secret of the Long Life of a Good Holobiont

Liliana Lippi, my mother in law, died last week at 101. You see her  in a picture taken for her 101th birthday, last July. with her two daughters and her son (on the left, my wife, Grazia). She also had four grandchildren and two great-granddaughters. What was the secret of her long life? Probably not a single factor, but perhaps the main one was that she managed to attain a certain harmony with the people and the things that surrounded her, as a good holobiont should do. 

I already wrote about Liliana's Longevity in a previous post published for her 100th birthday. Here is a longer and updated version.

Liliana Lippi was born in Florence, Italy, in 1920. She arrived into a completely different world from the one she left. When she came of age, in the 1930s, there were no TVs, no refrigerators, no supermarkets, no fast food, few homes had phones, very few people had cars. And her home had no central heating system: in winter she would sometimes wake up in the morning seeing that the water in the washbasin near her bed had frozen solid at the top. 

Her life as a young woman was typical of that age, when middle-class women, as she was, were supposed to be housewives and no more. She could cook, sew, clean, and perform other household skills. She never learned how to drive a car -- she couldn't even ride a bicycle. As most Florentines at that time, she couldn't swim and she was always a little afraid of the sea. No one remembers having ever seen her in a swimsuit. 

That doesn't mean her life wasn't rich in emotions and satisfactions. She had several suitors and the one who finally could touch her heart was a young Sicilian student who was studying at the Art Institute of Florence, close to where she lived. You may wonder how courting could take place in an age without telephones and social media: Liliana told me that the boy she eventually married would walk up and down along the street where she lived until she noticed him! You can find the same technique to get the attention of girls in Boccaccio's Decameron, written six centuries earlier! Probably, Sumerian boys would do exactly the same thousands of years ago. 

Liliana's sentimental life was adventurous. One reason was that, at the time, it wasn't so usual for a Florentine girl to have a Sicilian fiancé. Southerners were often shunned in Florence, just like Africans are, nowadays. Consider that the family of the boy (Giovanni) was not rich, and you have a recipe for contrasts in the family. Liliana's father, Mario, was never happy about this prospective marriage, but one of the characteristics of Liliana's personality was that she was stubborn about her choices. She wanted that boy and she had him, despite all that happened, including the war starting, Giovanni being drafted and sent to fight in Africa, then coming back to Florence and being wounded at a leg in a gunfight among the factions battling in the civil war. 

Eventually, Giovanni and Liliana did manage to get married in 1946. Then, they both moved to Sicily over a slow steam train that took two days to travel from Firenze to the city of Messina, where Giovanni's parents lived. Liliana remembers Sicily as an exotic place: a sort of wonderland. She and Giovanni were met at the train station by Giovanni's relatives who had arranged their transportation using a traditional, brightly colored Sicilian cart pulled by a donkey. And the Sicilians, in turn, were awed by this Florentine girl whom they considered a princess, of a sort. 

It seems that Liliana had a good time in Sicily, the problem was that there was no job there for Giovanni and that the home where they were living hosted the whole family, Giovanni's parents, and his sisters and brothers. When Liliana got pregnant of her first child, they came back to Florence where they settled in the house that her grandfather had bought for the whole family. Giovanni worked as a woodcarver, a skill he had learned at the Art School, while Liliana was a housewife. She had children, grandchildren, and even great-grandchildren. Giovanni died in 2003 at 89, Liliana survived him for almost two decades, dying at 101 in peace at her home, in her bed, surrounded by her children. She had been living in that same home since 1929. 

Despite some problems typical of old age (mainly arthritis), Liliana lived a reasonably healthy life up to her last 2-3 weeks. Remarkably, up to the last moments, she showed no signs of dementia, so common with old people nowadays. Of course, she would forget things and sometimes lose track of the conversation, but 15 days before dying, she was still sewing without needing glasses. Up to the very last day, she recognized her children and she was obviously happy to have them close to her. 

So, what was Liliana's secret for such a long life? Diet, exercise, medicines? Or what?

Let's start with food. Among the things she never ate there was junk food: pizza, hamburgers, Chinese food (she didn't even know what Chinese food was), or soft drinks. She didn't drink alcohol, not even wine. About what she ate, hers was a relatively high-protein diet in the form of eggs, chicken and rabbit meat, and also the boiled meat used to prepare the soup, a habit reported to have scandalized the British travelers who visited Florence at the time of the "Grand Tour. She also loved the fat part of the meat, including the fat coming with prosciutto (ham). She also drank milk every day, in the morning and before going to bed. About carbohydrates, she ate bread, very rarely sweets, and she was also fond of the kind of Italian soup we call "minestra in brodo." Personally, I hate it but maybe should reconsider after seeing how well it worked with her! In terms of vegetables, Finally, she was not especially fond of vegetables, which always appeared cooked at her table-- she seemed to be somewhat suspicious of salads. In short, not a ketogenic diet, but surely not vegetarian.

What else? She didn't smoke, she drank a little coffee, but that was her only recreational drug. She had an active life, but she wouldn't even dream of "exercising" in a gym or running along the street. She did watch TV, a little, when she was free of the various chores at home. But she never was interested in the news or in politics. Not an intellectual, she was nevertheless a voracious reader of all kinds of books, newspapers, and magazines.  

In terms of medicines, she avoided them as much as possible. When she was in her 70s she was found to have very high blood pressure and her doctor had her taking the full spectrum of pressure-lowering drugs: beta-blockers, diuretics, and other stuff that I can't exactly classify. I don't know how effective these drugs were. In any case, she never took statins to reduce her cholesterol level which was supposed to be in the normal range. Or maybe not, I have no idea of when she last checked that, possibly 10 years ago or more. 

During the Covid period, her physician insisted to vaccinate her with the Pfizer thing, last spring. I don't think it had any effect, good or bad, we never had her tested for the coronavirus since she showed no symptoms of it. What I can tell you is that we never isolated her, never had her wear a mask, her relatives newer wore a mask when staying with her, and we never prevented her from seeing her great-granddaughters. She enjoyed their company a lot, nearly up to the last moments of her life.

In the end, I don't want to stretch too much the analogy with holobionts, but there is something in living a good and long life that has to do with attaining that kind of harmonious equilibrium that is the characteristic of holobionts. They are creatures living in symbiosis with each other in a non-hierarchical network. We humans can do that if we are well connected with the other humans surrounding us. Of course, there does not exist a perfect set of interactions but, on the whole, is the way we are built to live: part of the human social holobiont. 

Liliana surely was a good social holobiont. I told you that she was stubborn, but that was when it was about herself. With the others, she was very flexible, never trying to impose anything on anyone, accepting things as they came.  And she had a rich social life: her home was always open to relatives and friends coming for lunch -- she was the hub of a remarkable network of interactions among people. No one seems to remember her going mad at something or someone. Maybe this is the secret of a long life, maybe not. And so it goes. 

Here is Liliana for her 100th birthday. You see with her daughter (Grazia) granddaughter (Donata), and great-granddaughter (Aurora). All of them are daughters of the Goddess Gaia, connected over nearly one century of life, a snapshot of the great chain of beings that keeps turning and turning, and has been doing that for billions of years, and will keep doing that for many more years. 

Meeting the Goddess Gaia in a Supermarket!

Maybe this image is not so impressive as you would expect the Goddess of Earth, Gaia, to be. Still, it is remarkable that nowadays you can walk into a supermarket and then, suddenly, be exposed to an epiphany of the Goddess herself. 

No doubt, it is her. Gaia, sometimes compassionate and merciful, and sometimes cruel and ruthless. She who rules the ecosystem, she who embodies the ecosystem, she who is the ecosystem. Gaia, the supreme holobiont, the ultimate living being, the apex of the great ecosystemic fractal, the product of billions of years of evolution. 

And there she is, smiling and at ease among the aisles of a suburban supermarket. Perhaps just the place where she should be as the Goddess of abundant life. 

Anastassia Makarieva Speaks About the role of Forests in Protecting Earth's Climate

 

Anastassia Makarieva in a recent talk recommendsed the preservation of the natural forest holobiont:

International climate discourse mentions forests in two contexts: as carbon deposits and as renewable sources of materials and energy.

If implemented in global policies, this narrow view on forests can, contrary to expectations, worsen climate destabilization. Two crucial aspects are undervalued and understudied.

The first is the major role of forests as regulators of the various aspects of the water cycle, including cloud cover (a major source of climate uncertainties) and ocean-to-land and transcontinental transport of atmospheric moisture.

The second is the difference in the environmental functions of primary forests, largely unperturbed by anthropogenic activities, versus exploited tree stands. While the former have evolved to maximize environmental homeostasis, the latter were selected to maximize economic productivity. The two cannot be maximized simultaneously.

Successful strategies of climate change mitigation should prioritize preservation of still extant self-sustainable natural forests for humanity to continue benefiting from their climate stabilization potential.