Saturday, December 19, 2020

The Secret of Holobionts

 


"Braiding Sweetgrass" is a wonderful book, the kind that's best digested a few pages at a time. (h/t Erik Assadourian). In it, the author, Robin Wall Kimmerer, happily moves back and forth from the uses of her Native American ancestors and her knowledge as biologist. She never uses the concept of "holobiont," but the book teems of holobionts on almost every page.
 
I am about halfway through it, and the book remains full of surprises. Here is what I read this morning, while drinking my coffee. It is about how the ancient Native Americans had found a way to optimize their plots of land by planting together three different seeds: corn, beans, and squash, poetically referred to as the "Three Sisters." Kimmerer goes on describing the details of exquisitely intricate ways in which these three species collaborate with each other, maximizing the supplying of nutrients to all three. She says.
 
"It’s tempting to imagine that these three are deliberate in working together, and perhaps they are. But the beauty of the partnership is that each plant does what it does in order to increase its own growth. But as it happens, when the individuals flourish, so does the whole. In reciprocity, we fill our spirits as well as our bellies."
 
And that's the true secret of holobionts.



Thursday, December 10, 2020

On the Importance of Having Limbal Rings. The Evolution of Humankind

 

 
 
 
This short movie, Vikaari, has recently appeared on the "Dust" site and I think has several interesting features, relevant to the concept of holobionts. 
 
It is very well done as a movie, although it is deeply contradictory in many aspects. For one thing, it is a narrative disaster. First, the movie tells you that the Vikaari, children born without a visible iris in the eyes, are good people, and the target of Nazi-like bad guys. Then, we see the Vikaari killing their pursuers using their psychokinetic powers in bloody and cruel ways, apparently without any regret. Needless to say, this completely destroys the narrative tension of the movie and leaves you totally baffled about what the filmmakers wanted to say.

Indeed, I think the filmmakers were badly confused on several planes. First of all, in their decision of presenting this "new race" of children as something that will replace current human beings, engaged in destroying their own planet. Is this a hope or a fear? Difficult to say, but surely evolution doesn't work in that way. 

And then, why the choice of iris-less eyes as a defining mark? Most people rarely consciously perceive the characteristics of the irises of their fellow human beings. But the shape of the iris tells us much of the genetic inheritance of a person -- on this point, the film-makers got it right, although in reverse. A human being without a visible iris is not a modern human.
 
The iris is an easily modified, highly visible human trait. There is a whole genetic story in the human iris. From what we can say, light-colored eyes have been rare, although DNA studies indicate that they did exist in the Mesolithic period. Curiously, Europe is the continent where, nowadays, light-colored eyes are most common. But it is only a few centuries ago that light-colored irises start to appear in paintings. If they had existed before, surely painters would have noted them and shown them in their paintings. Green eyes are a modern trait in Europe, they seem to come from Northern Asia. They do spread easily because they are a typical "epigamic" trait. They give a certain advantage in the sexual competition for mates. 
 
And then, there are limbal rings. The dark ring that surrounds the iris. Also a typical epigamic signal, they are likely to be a feature of the modern main organism of the human holobionts. Here you see the eyes of Sarah Brightman, a modern human specimen, notable for their light green color and well detectable limbal rings. As epigamic signals go, Ms. Brightman is surely beaming them out loud and clear!
 

Note the difference from other mammalian eyes. Most animals, even our close relatives, the apes, have dark eyes, no limbal rings, and not even a large and well detectable sclera. You see it in the image: this (probably) female bonobo doesn't look at all like Sarah Brightman, although she also surely sends powerful epigamic signals to the males of her species. 
So, why do the Vikaari of the movie have no irises and no pupil? They are, actually, the specular version of the "black eyed people," characters of a recent horror movie. In both cases, filmmakers understood that the lack of sclera or of the iris is a characteristic of a creature that is not fully human. A new species (as in Vikaari) or an otherworldly evil creature (as in "black eyed creatures"). No wonder that regular humans react with great perplexity and sometimes violently. And their violence is reciprocated in Vikaari
The existence of these films shows our limited understanding, and also limited tolerance, of what makes humans human. A small difference in the extent of the sclera or in the color of the iris is sufficient to turn otherwise fully human creatures into enemies, at least in these fiction pieces. But we all know very well that it happens also in the real world for other, no more important genetic traits, such as skin color. 
 
There is a thin line that separates the horrible from the attractive: nobody would be killed for having green eyes, but the white-eyed Vikaari could be if they existed for real. But that's the way evolution works. Sometimes gradually, sometimes in bumps. The human holobiont of the future will not be the same as it is now and it was in the past. It is the giant holobiont that we call the ecosphere that changes all the time. Onward, fellow holobionts!


Finally, for your curiosity, the "Statue of a Standing Nude Goddess," presently at the Louvre Museum and coming from excavations in the Middle East. Note the eyes without irises. It is not clear if that was a bug or a feature: once they had decided to use rubies for the eyes of this statuette, there was no way they could have shown irises or pupils. But maybe it was intentional: this figure may have been supposed to be somewhat otherworldly or even threatening. Note the horns on her head, a typical attribute of the Moon Goddess. Already at the time when it was made, probably the 2nd century CE, goddesses were rather unpopular and suspicious, not unlike our modern witches. 


 
 


 

Friday, December 4, 2020

The Loving Reaper as a Holobiont. An Interpretation by Jenny Jinya


I don't think I'll engage in commenting the details of this story by Jenny Jinya, the young German lady who has been creating incredible stories (see here, here and here.). After all, we all know that the way to boredom lies in telling the details. But try to take a look at this story. It is not just a moving story, it has an unbelievable depth. It resonates of so many motives and ideas that are part of human history that it left me breathless: the Goddess, Death, the Otherworld, kindness, piety, benevolence, mercy, and much more. 

But the bewildering element of this story is how all these things are linked together. Jenny Jinya has truly understood how the universe works: life and death need each other and neither could exist alone. The holobiont concept is not just about symbiosis, it is about communication. And the universe is a giant holobiont that moves, changes, grows, shrinks, expands, returns, and restarts, all because its elements communicate with each other and the result is the never-ending cycle of life and death. Sometimes, we use the term "love" for this kind of communication and it is truly the most powerful force in the universe.







 

 

Thursday, December 3, 2020

Can Plants Perceive Us? The Opinion of Professor Suzanne Silard

 


What could be more holobiontic than this? Words of Suzanne Simard, as reported by the New York times.
 
“I think these trees are very perceptive,” she said. “Very perceptive of who’s growing around them. I’m really interested in whether they perceive us.” I asked her to clarify what she meant. Simard explained that trees sense nearby plants and animals and alter their behavior accordingly: The gnashing mandibles of an insect might prompt the production of chemical defenses, for example. Some studies have even suggested that plant roots grow toward the sound of running water and that certain flowering plants sweeten their nectar when they detect a bee’s wing beats. “Trees perceive lots of things,” Simard said. “So why not us, too?”




 

Sunday, November 22, 2020

A New Holobiont in Gaia's Family

 


Had you ever heard of the "Plastisphere"? Well, it is a new ecosystem that thrives on the plastic islands in the sea created by human activity. 
 
The term was coined in 2013, but these little critters are still thriving nowadays as you can see in a more recent article
 
For sure, they'll soon have plenty of food in the form of the six billion (yes, 6x10^9!) plastic face masks discarded everyday by humankind and, eventually, ending up floating somewhere in the ocean. 
 
And here is how the plastic plate appears to our little friends, the microbes. Bon Appetit!
 
 


Friday, November 20, 2020

The Wolf Song. A Few Minutes of Bliss in a Difficult Time


A splendid song, splendidly sung by Jonna Jinton, Swedish singer. The images are haunting and beautiful, suggesting the beauty of the forest inhabited by wolves, humans, and other creatures that form a single system, holobionts within the greater holobiont that covers the land. A few minutes of bliss, welcome in the difficult times we are living. 

These are the words in Swedish ("vargen" means wolves) -- Here you can find a more traditional version. Note how gentle and compassionate is the song, with the mother understanding the hunger and the distress of the wolf and willing to give it a pig tail or a chicken shank.

Vargen ylar i natten skog
Han vill men kan inte sova
Hungern river i hans varga buk
O det är kallt i hans stova
Du varg du varg, kom inte hit
Ungen min får du aldrig
Vargen ylar i natten skog
Ylar av hunger o klagar
Men jag ska gen en grisa svans
Sånt passar i varga magar
Du varg du varg, kom inte hit
Ungen min får du aldrig
Sov mitt barn i bädden hos mor
Låt vargen yla i natten
Men jag ska gen en hönsa skank
Om ingen annan har tatt den
Du varg du varg kom inte hit
Ungen får du aldrig
Ooo
Ungen den får du aldrig

And here is a version in English (translated using Google, revised using common sense, as I don't speak Swedish. May not be perfect).

The wolf howls in the night forest 
He wants to but cannot sleep 
Hunger tears in his wolf belly 
Oh, it's cold in his den
You wolf you wolf, do not come here 
You'll never get my kid 
The wolf howls in the night forest 
Howls of hunger and complains 
But I'm gonna give it a pig tail 
That kind of thing fits in wolf stomachs 
You wolf you wolf, do not come here 
You'll never get my kid 
My child slept in her mother's bed 
Let the wolf howl at night 
But I'm gonna give it a chicken shank 
If no one else has taken it 
You wolf you wolf do not come here 
You never get the kid 
Ooo 
My kid, you'll never get it


Friday, November 13, 2020

Sex Among Holobionts: Love is a Horizontal Thing

 


  Marc Chagall (1887-1985) is reported to have said, "Only love interests me, and I am only in contact with things that revolve around love."  His paintings have a certain "holobiontic" quality. This one, "Les Amoureux de Vence" was painted in 1957,

 

What do holobionts, empathy, and harmony have in common with sex? One thing: they are all forms of horizontal transmission of information. We tend to see ourselves as multicellular organisms and, for us, sex is indeed a "horizontal" thing, in a certain sense. 

But, sex was not invented by multicellular thing. On this planet, sex is mostly something that bacteria engage in, freely exchanging genetic materials among themselves. It is free love that goes on all the time among single-celled creatures. And it is the way they evolve. It is by exchanging genetic materials that bacteria have become more and more capable to resist to the human attacks against them by means of antibiotics.

And even viruses, which can't reproduce by themselves, have sex with each other. It is just that they can only do that when two different viruses find themselves in the same host cell. That can become even a little weird when the two viruses come from different previous hosts, say a pangolin and a human being. In any case, viruses evolve very fast, that's why almost every year a new wave of influenza spreads over the world. 

For larger holobionts, such as human beings, the situation is different when you consider the reproductive mechanism of the main organism, the human one. Two human organisms exchange genetic information, but then this information must be "read" in a complex process that involves the birth of a new human being (and, unfortunately, the death of the old one). It is slow: in terms of evolutionary prowess, viruses and bacteria run circles around us. Fortunately, our immune system can also change fast enough to match the new threats and we are also defended by the "good" biome that form the human holobiont, the bacterial and viral symbionts we carry with us. And we are part of the larger holobiont we call the ecosystem.

Holobionts are a fractal system: the true embodiment of the poem of Jonathan Swift

The Vermin only teaze and pinch
Their Foes superior by an Inch.
So, Nat'ralists observe, a Flea
Hath smaller Fleas that on him prey,
And these have smaller yet to bite 'em,
And so proceed ad infinitum:

And so it goes.



Thursday, October 29, 2020

Biophobia: one more example of our fear of Nature and of ourselves

 

 

A clip from "Dust."  They are a company specialized in airing short sfi-fi films. The quality of what you can see is very variable, goes from the boring to the silly, includes the very clever, and sometimes true gems. 

I thought I could inflict on you this clip not because it is especially good, but not so bad, either. It may be good as entertainment. It has distinct "1950s" feel and it could go in the same category as the old "The Creature from the Black Lagoon." What's strange is that it was made in 2020 and one could think we had overcome that attitude of old that saw non-human creatures as monsters. 

Here, we have a good example of the current wave of "biophobia" -- it is the story of a young woman who is bitten by a mosquito. Then, the mosquito flies to meet a subterranean monster who uses the genetic information contained in the woman's blood to create a clone of her.

As I said, not bad as entertainment but, as biophobia goes, this is the way many of us see the creatures that surround us. Creatures to be kept away from our bodies as much as possible, least we'd be contaminated. And, in the end, I think the clip has a logic that perhaps even its authors didn't realize: it is our fear of sickness, our fear of death, our fear of bodily decay. All amplified by the tiny monster we call coronavirus -- a name that brings a hint of  the crown that death used to wear in medieval iconography, a symbol of power.



All fears that have taken over our minds everywhere. And how the woman of the clip sees he double is as she sees herself as in a mirror. It tells us a lot of how we see ourselves nowadays. We are scared of our fellow human beings, a monstruous, innatural, unimaginable (up to now) feeling. It is, first of all, a sickness of the mind. We will not be healed we come to a pact with nature, only then we'll be able to understand who we are. Onward, fellow holobionts!

  

 

Wednesday, October 28, 2020

Braiding Sweetgrass

 



A contribute by Robinne Gray

 
When Erik asked me about potentially leading a book discussion, I told him there are two books that really rocked my world(view), one is Robin Wall Kimmerer's Braiding Sweetgrass The other is Thomas Berry's The Great Work, which I'd love to revisit in 2021.

For those unfamiliar with this book and author, a little enticement: Robin Wall Kimmerer is a Potawatomi woman who is also a plant ecologist and professor in the SUNY College of Environmental Science and Forestry. So she is uniquely positioned to bring together two very different ways of engaging with the natural world in a way that (IMO) the world really needs. It helps that she's a wonderful writer, so her work is getting a lot of attention and inspiring many people. 

I'm a lifelong reader who hasn't participated in many book discussions because I'm stubborn and only want to read what I choose and when - and also because I don't always finish a given book in a timely way, and may be reading several books at once. An encouragement I offer is: Braiding Sweetgrass is a series of essays, so even if you make time to read one or two of them to get a taste, it would be wonderful to have you be part of our discussion of this rich work!  I've included a quote from the book below.


 Note: this text appeared in the discussion group "Gaian Conversations" kept by Erik Assadourian and is published here by kind permission of the author. If you are interested in joining the discussion group, write to Erik at info(thingything)gaianism.org


 

Monday, October 26, 2020

Where you could buy live lice in Florence, 50 years ago.

 

According to what I heard from the people who remember these things, I think I was able to locate where you could buy live lice in Florence to swallow to cure your jaundice. A typical holobiont thing to do. 

The old lady who sold these lice lived - I believe - in the house with the small arched door of this street called "Via Camaldoli." She was called "La Pidocchina," that is, "the little lady louse."

I didn't try to ring the bell to ask if someone in there still sold live lice. But, who knows?



Wednesday, October 14, 2020

The Truth about Lice Revealed. A new discovery about the human holobiont

 "Lice Capades," an episode of the TV series "South Park." Lice are being understood as an important part of the human holobionts and, who knows? One day they may be considered as an essential component of human health, just as gut bacteria. 

 

Today I had a little revelation on lice. I had been writing about some recent discoveries on the beneficial effects of lice on human health and I had reported a story that I heard from my wife about people swallowing live lice as a remedy for jaundice (hepatitis b). And of people in Florence selling lice just for that purpose. But I wasn't sure if it was a real story or a legend. 

But, today, I heard a talk by Maurizio Naldini, a Florentine journalist, who told several stories about the Florence of his youth. And, yes, he had met in person the woman who sold lice! It was true: people would buy lice in Florence as late as some 50 or 60 years ago. 

The curious thing about this story is that Mr. Naldini had no idea of why people bought lice and what they did with them. So, he listened with great interest to my wife telling him the story of lice being swallowed inside a wheat wafer to cure jaundice. 

In my case, hearing Mr. Naldini had a different effect. Now that I knew that the story was most likely true, then I could examine it more in depth. Of course, the idea that lice would suck out the bile of jaundice makes no sense. Swallowed lice (dead or alive) can hardly suck anything. But then, why would people do such a thing? 

Of course, there is a tradition for people paying good money to do the strangest things when they are sick and they think something can help. CBS has a list of the 15 most bizarre (and disgusting) cures ever invented, and it is surely interesting to learn about such ideas as placing a dead mouse in the mouth to cure toothaches or using crocodile dung as a contraceptive. But they don't mention lice!

Yet, even the most bizarre ideas have an origin and I think that the lice market of Florence had a justification, probably better than that of crocodile dung. It has to do with the concept of holobiont, the fact that the human body (just as that of most animals) is an incredibly complex assemblage of creatures. Most of them very small (bacteria and viruses), some a little larger (lice and others), and with the actual human organism as just one of the many, although surely the biggest. 

Now, holobionts exist, and if something exists it means there are good reasons for it to exist. Most of the creatures that populate the human holobiont are there for a reason. Maybe they are just harmless commensals but in many cases, they are useful symbionts. And that may well be the case of lice, too. 

I already mentioned a study that found "Unexpected Benefits from Lice." The little critters seem to boost the human immune system. But there may also be another benefit. You see, there are three kinds of lice inhabiting the human holobiont: the body louse, the head louse, and the pubic louse. 

Of these three, the only one that may be harmful to human health is the body louse. It may be because it is a relatively recent human parasite having developed in parallel with the use of clothing. But another study argues that the "good" head lice can be beneficial in stimulating the development of an immune response against the "bad" body lice. So, if you have (or have had) head lice, you are healthier.

Perhaps this is the key to the story of the market of lice in Florence. Ancient Florentines knew little about immunity, but they may well have noted that people who had head lice were less prone to have body lice. Perhaps even that head lice could help people get rid of body lice.  Lice don't jump around or fly, so moving from one body to another is not so easy. And so they would ask their friends and relatives if they could give a hand in passing lice to someone who was lice-deprived. Then, why not? Some enterprising people thought they might make a little cash by providing others with a commodity that was needed: lice. 

Maybe this was the origin of the legend that my wife told me. Once that lice were understood as beneficial, it was natural that they could be tested on other kinds of illnesses. Then, the placebo effect would convince people that lice were effective in curing jaundice. With the more enlightened (so to say) 20th century, lice of all kinds became anathema and a social stigma, But the idea that you could eat lice in a wafer to cure a rather stubborn illness such as jaundice remained for some time. 

It is an interesting story that goes in parallel with that of the discovery of the bacterial flora in the guts. Some people understood right away their importance and their beneficial effects, but others thought that it was not hygienic having bacteria in your guts and thought it was a good idea to get rid of them. Now, of course, you buy probiotic supplements just to get more good bacteria inside your guts. Who knows? Maybe one day it will be fashionable to buy head lice in a pharmacy in order to prime people's immune systems!

And this is the story. The more things you know, the more you discover. And so, onward, fellow holobionts!

 

Note: After publishing this post, I received a link from Jan Barendrecht to a paper that describes how swallowing lice was considered a therapy for several kinds of illness in Spain. But not just in Spain. The authors say that: 

Numerous authors show that using animal resources as therapy is a widely distributed atavistic practice [,], a fact that is demonstrated by the use of head louse against jaundice in distant geographical areas [,]. Its use is particularly common in the Hebrew culture. Izaak Walton in his famous book “The Compleat Angler” (published in 1653) records that the Jews were the first to say that swallowing live lice is a good remedy for jaundice []. For their part, the German rabbi Yair Bacharach (1639–1702), author of the collection of responsa known as “Havvot Yair” (“Villages of Yair”), indicates that the patient should take 8 lice taken from his/her own head–see Rosner and Bleich 2000 []. Ben-Ezra in 1949 recorded in Horodetz (one of the oldest Jewish communities in Russia-Poland) the introduction of lice in an omelette as treatment []. In Latin America there are also references to this medical practice. In this case, the remedy would have been brought by the Spanish conquistadors and assimilated by the Spanish American folk medicine in an eclectic form []. The recommended number of specimen to take in Chile, Peru, Guatemala and Argentina is 4 or 5 with examples found using measures such as a thimbleful [-].




Saturday, October 10, 2020

It is a Lion! It is a Goat! It is a Snake! No! It is a Holobiont!

 

Maybe 25 years ago, my friend Susan came from California to visit me in Florence. She saw the statuary piece of the Chimera of Arezzo and asked me what that was supposed to mean. I said, "I don't know for sure, but I'll find out." 

That involved much research, papers written, a blog created, and an entire book in Italian. And yet, I can tell you that I was yesterday night that understood what a Chimera really is. Just before falling asleep, I had this flash: here is it: A holobiont! So obvious!

And that's no mere definition: it opens up a whole new layer of interpretation of the chimera as a horizontal contamination of memes. Memes do replicate horizontally, just like bacteria do. Truly mind-blowing, I am still shocked by what I was thinking yesterday night. 

There will be more on this, but for the moment I just wanted to mention this discovery to you. Life is beautiful when you can think of such things!



Wednesday, October 7, 2020

How Your Gut Microbiome can make you Smart or Dumb

 


Deric Bownds discusses how fecal transplants from old mice to young mice have bad effect on the critters' mental abilities. Maybe the opposite is also true. And maybe it works also for humans.
 
It seems that your microbiome can make you smart or dumb. Holobionticity is a complex matter, indeed! 
 

Age related cognitive decline and the gut microbiome

by Deric Bownds

Haridy summarizes experiments by D'Amato et al. showing that fecal transplants from old mice to young mice result in the younger animals displaying learning and memory impairments. It would be interesting to expand this work to check whether transferring fecal transplants from young to older mice improved their learning and memory, as is the case with blood transfers from younger to older mice. Here are the background and results sections of the open source research paper



 


Saturday, September 26, 2020

Unexpected Symbionts: What if Your Health could Benefit from Creatures you Normally Despise?

 

"Lice Capades" (2007). An absolutely wonderful episode of the "South Park" series. The world as seen from the viewpoint of lice. Fantastic. 


In Italy, there is a legend that says you may be cured of hepatitis b (jaundice) by eating lice. It is not just a vague legend, I personally know people who swear they were cured of jaundice by doing exactly that. Apparently, in the 1960s, there were still people who sold live lice packed in a small wafer (where they got the little beasties is anybody's guess). No trace of this story can be found on the Web nowadays, I can only relate it from what relatives and acquaintances tell me. But I have no reason to doubt that it was a common belief some 50 years ago, although it may have been limited to Tuscany, or perhaps only Florence. There are reports of people eating lice in other cultures and, of course, monkeys, apes, and other furry animals do that all the time. 

About this story, let me say that I am a big fan of evidence-based medicine and I am the first to doubt this story (and, also, I never had lice in my life). But, once you acquire the concept of "holobiont," you start reasoning that lice must have accompanied the human organism for millions of years. And, if they did, there has to have been some reciprocal adaptation and -- why not? -- mutual benefit. Of course, as a human being, you won't even remotely imagine that lice may be good for your health. But are you sure? 

At this point, you start searching the web and, surprise! (or maybe not), you immediately find an article titled "Unexpected Benefits from Lice" Look, this is serious stuff, evidence-based, not old folks' tales. And they say: 

Parasites such as lice have a role in the conditioning of a 'natural' immune system and reducing the likelihood of immune dysfunctions,

Of course, that's true for mice, but there is no reason to believe that it wouldn't work for human organisms, as well. Some people have said exactly that, "lice can be good for you." Maybe that's a bit optimistic but, surely, there is no reason to fall into hysterical reactions when dealing with lice in children. In some cases, lice may be bad for your health, but the little critters are not a major threat.

So, may lice be a symbiont rather than a parasite? As usual, the boundary between the two categories is fuzzy. Likely, no creature living inside the human holobiont is 100% parasitic. Most of those that lived with us for millions of years surely have at least some beneficial effects. And let me tell you just one thing: my mother-in-law holobiont had flatworms for most of her life. She turned 100 two months ago and she is in reasonably good health for her age. Would there be a correlation? At least, you can't rule that out!

You see how ideas interlock with each other and branch out generating new ones? Once you have the concept of holobiont, you have access to a whole new host of concepts. It is the beauty of the world we live in: truly Gaia takes many forms!



Saturday, September 5, 2020

The Evolution of Human Empathy: From bronze age warriors to us, and beyond

 The human mind is the most complex entity we know in the whole universe. One of the fascinating things about it is how it has been evolving over time. What could have been the thoughts of a bronze age warrior? What thoughts did an ancient hunter-gatherer think? Why do we think the way we do, nowadays? As Sir Thomas Browne said, these are puzzling questions, but, like the song the Sirens sang, not beyond all conjecture. And here I am presenting a sweeping review in this area that starts with the work by Julian Jaynes on the mind of our remote ancestors, connects it with the most recent result of genetic studies, and even tries to peer into the future: how will the human mind evolve? Another question not beyond all conjecture. We may be moving toward much more complex and intricate forms of empathy than those we know nowadays.

 

The Mind

The mind is a tool, this much is clear. Of course, it is a special tool, able to do many things in many fields. But it is a tool and it has evolved to perform the tasks it performs. Do you remember Darwin's finches? They are birds with beaks of different shapes that were the source of inspiration for Darwin's idea of evolution: the beaks adapted to the different kind of food eaten. The human mind does the same. If it is like it is, nowadays, it is because it is functional to what it does. 

That applies also to the entity we call consciousness. We can define it as the capability of "modeling oneself" just like we can model other people's behavior in order to predict it. You probably heard the story of the "mirror neurons," brain structures specialized in understanding the behavior of other people. In a way, it means reading other people's mind. Your dog can do the same: dogs have mirror neurons, too. You can use the term "mirroring" or also "modeling." It doesn't matter the term. if you can model other people's behavior, you have a certain degree of empathy. And, very likely, high empathy and self-consciousness go together. They are two axons of the same neuron. 

Empathy is surely useful for us in many circumstances (also for dogs). You need to know if the person you have in front is there to help you or he wants to use his battle-axe on you. But that doesn't require much effort in terms of sophisticated mind-reading. Where modeling truly shines as an evolutionary tool is in the mating game. At least in our modern world, the competition for mates is fierce and ruthless and it involves many factors. Surely money and status count, but empathy does a lot as the capability of mirroring your perspective mate means behaving in a way that you know that he/she will appreciate. Ask any pick-up artist about that and he'll confirm that it is the tactic they use. Also, if you ever chatted with a professional sex worker, you may have noted how they have an uncanny ability of reading your mind and say exactly what they know will please you. The whole game is played by modeling another person's mind inside one's own.

So, it is no surprise that most of the modern literature and fiction deals with what we call "romance," men and women getting together. We seem to be deeply interested in the courtship rituals and about everything involved with it. It is one of the top skills of our mental arsenal. But have we always been like this?

 

The Evolution of the Mind

At which point in their evolutionary history did humans develop this exquisite ability of reading each other's minds -- including their own -- that we have today and we also call empathy? There are cartoons that describe cavemen using their stone axe to stun a woman before pulling her by the hair all the way into their cave. But that's of course a little unlikely to have ever been our ancestors' behavior, to say the least! But how did cavemen woo their women? Of course, the entity we call the "mind" leaves no fossil record, so what do we know about the empathy capabilities of our remote ancestors?

The first to pose this question was Julian Jaynes with his "The Origin of Consciousness and the breakdown of the bicameral mind" of 1976. It was a milestone in the field: Jaynes analyzed ancient written records and he concluded that the people living during the bronze age were not really "conscious" in the modern sense of the term. They had what Jaynes called a "bicameral mind." They would "hear voices" in their minds and act accordingly, but we have no evidence that they had the kind of self-recognition that we normally have today.  

The idea of the "bicameral mind" as described by Jaynes has been often criticized and, indeed, there is no proof that the inner mechanisms of ancient minds worked the way he proposed. But it doesn't really matter whether the "voices" are the result of the interaction of the two halves of the brain or they originate in some other sections of the brain. The point is that the behavior of the people described in such documents as the "Iliad" or some books of the Bible is completely different from that of modern people. The ancient just seem to lack empathy, they act like automata, without evident feelings of love, compassion, or concern for other people. In modern terms, we would define bronze age people as "autistic." Maybe it is a literary style, but Jaynes' idea that people truly behaved in this way makes a lot of sense. 

Just as an example: think of the Iliad. The story start with Paris, a Trojan prince, stealing Helen from her husband, Menelaus, king of Sparta. Then Paris is killed, and Helen marries another Trojan, Deiphobus. Finally, Menelaus kills Deiphobus and takes Helen back. Does the Iliad report of anyone caring about what Helen feels during these events? Was she unhappy, concerned, sorry, or what? No -- nobody gives a war cry about that. Another example: consider the case of  Tamar and Judah, as reported in the Genesis. In the story, the only problem for Tamar is how to give children to Judah's clan despite the death of her first and second husband, both sons of Judah. And nobody cares about what Tamar feels. Nor, there is any feeling or care for what Tamar's husbands feel, or pity for their fate.

Now, let expand the discussion a little. Jaynes had only written data, so his analysis couldn't go further back than the 3rd millennium AD, more or less. Before that age, there are no written records, at most pieces of statuary that might be interpreted in various ways, but that don't tell much to us about how people thought or behaved at that time. 

But we now have genetic data that, amazingly, give us a chance to go well  beyond the "literacy limit." I refer to the recent discovery of the "Y-chromosome bottleneck" in humans (Karmin et al., 2015). I described these findings in some detail in a previous article on "The Proud Holobionts." Here, let me summarize these results.

 

The figure above, (Karmin et al., 2015) reports the degree of diversification of the human Y-chromosome and of the mitochondrial DNA (mtDNA) over time. Both are elements of the genome that are passed only from male to male (Y-chromosome) and female to female (mtDNA). So, the curves are roughly proportional to the active male/female reproducing population. 

For most of the record available, some 50 thousand years, the population of reproducing males is smaller than that of the females, roughly a factor of three. It doesn't mean that there were less males than females in these populations. Then as now, the male/female ratio for the people alive at any given moment was approximately equal to one. But not every human being manages to leave descendants: many disappear from the genetic history of the species. For some reason that would be long to discuss, females are normally more successful than males at that and that's what we see in the curves of the study. 

But the study shows an impressive and unexpected feature. A "bottleneck" in male diversification that takes place between 7,000 to 5,000 years ago. In this period, there was only about one reproducing male out of 20 reproducing females. 

If we now compare with Jaynes' data, we see that he placed the bicameral mind as existing approximately during the 3rd-2nd millennium BCE, while the breakdown took place during the late 2nd millennium, roughly with the end of the bronze age. So, Jaynes' time window overlapped in part with the bottleneck. What he was seeing was the climbing side of it. He saw modern consciousness appearing (re-appearing?) with the male reproductive effectiveness gradually regaining the normal value of 1:3 with respect to the female effectiveness after a period of eclipse. But what does that mean?

 

Interpreting the data

We said that the conscious part of the human mind is mainly a tool used to find sexual partners. So, the mind must have adapted to the social and economic structures of society as they changed and evolved. Then, let's start from the beginning, the left side of the curve reported by Karmin et al. from ca 50.000 to 10.000 years ago. We see that during that period the average the reproductive success of human males was about the same as it is today, that is one male reproduced for about three females .

We know in those remote times, humankind was mainly practicing a hunting and gathering lifestyle. What were people's minds like at that time? Of course, we have no written records from those times. But we still have hunter gatherers around in our world, so that we can have some idea of how they think. Helga Ingeborg Vierich has lived with hunter-gatherers and she reports that they are kind and considerate, and rarely polygamous. In their societies, males have about the same chance as females to marry outside the group. Women have positive roles in society, separate but not inferior to the roles of males. On this point, I can also report my personal experience with the Roma (the Gypsies) who are perhaps the closest approximation to a hunter-gatherer society existing in Europe nowadays. In terms of empathy, I can tell you that their skills in reading the mind of a gajo (a non-Rom) are nothing less than exquisite. They need these skills in order to survive in a world where the gaji are a large majority. If empathy is a useful skill in a monogamous, relatively egalitarian society, then our hunter-gathering ancestors clearly had it, just like our modern hunter-gatherers do (and the Roma, too).

Then, there came the "bottleneck" that corresponds approximately to the end of the Neolithic and the start of metalworking, first copper then bronze. As it normally happens, technology changes society, sometimes very deeply. The bronze age saw people moving away from the traditional hunting-gathering lifestyle to that of farmers and pastoralists. It is normal (but with plenty of exceptions) that pastoralists tend to live in patrilinear "demes" (you can call them "clans"), a term used in biology to indicate groups in which individuals tend to mate mainly with other members of the deme. 

In human patrilinear demes, males tend to remain within the deme, while females are more mobile and move from a deme to another (it is called exogamy). In this kind of society, women marry a clan, not a person, just like Tamar did in the Biblical story. Even in the case of Helen of Troy, the story of her abduction may refer to a form of exogamy.

In this kind of patrilinear societies, we can imagine that there is little need for either males or females to develop the kind of empathy that we moderns need. Neither Paris nor Helen are reported in the Iliad to have been "in love" with each other in the modern sense of the term. There is nothing romantic in their relation. In general, if a woman marries a clan, then she doesn't care whether the male they mate with is nice, considerate, and gentle. What counts is how many sheep the clan has. Maybe this is a little schematic (a lot), but it seems to fit with what we know of the age described by Jaynes. 

These genetic data are in line with the interpretation that the age of the bottleneck corresponded to an increasing population of pastoralists living in patrilinear demes. This is explicitly discussed a 2018 paper by Zeng et al. They explain the bottleneck as due to evolutionary competition between demes, rather than individuals. A deme can "die" either because it is outcompeted by the others for scarce resources or because its members are killed in battle. Since the males in a deme are closely related to each other, there is a good chance that, when the deme dies, their Y-chromosome disappears from the human genetic history. Females, instead, owing to their exogamic habits are more likely to have their genetic signature survive, being spread over several memes. 

Can these social changes affect the genetic build-up of the human mind? We cannot say for sure, but don't forget how powerful evolution is in shaping the functioning of living creatures. The whole "bottleneck" episode lasted a few millennia and Cochrane and Harpending suggest in their "The 10,000 year explosion," that the human genome could change significantly in such a short time. For instance, they note that bronze age people had a significant brow ridge that was later mostly lost. Human females of the late bronze age didn't seem to like this feature very much in their males, just like modern human females don't. But no amount of cultural change can make you gain or lose a prominent brow ridge. It can only be genetic.

But it is not really fundamental to decide whether the big changes we see across the bottleneck are genetic or cultural: let's just say that they occurred, quite possible because of a mix of the two factors. Then, everything clicks together, more or less. The bottleneck was caused by the rise of a patrilinear society organized in small demes, then it disappeared when the demes were superseded by new social organizations: cities, states, and empires. Kings and emperors didn't want their subjects to fight tribal battles against each other. So, they broke the deme structure in various ways -- they never were able to eliminate them completely, but their importance was enormously reduced. With this, the old bronze age "bicameral" mind became obsolete. And evolution did its job: what is not needed or is harmful, disappears.


The rise of monogamy

Over the past 2-3 thousand years, we see a gradual tendency for rigid clans to disappear and a certain degree of egalitarian society developing. Monogamy becomes more and more common, at least for the average people (kings and emperors are not bound to their own laws). Monogamy was not only a social custom, but often enforced by laws and by religious commandments. The main reason for this development is that monogamy is a useful feature for a military empire (and all empires are). Armies need soldiers and cannot tolerate that soldiers fight with each other for females. Instead, if every male has one female, at least on the average, there is no need for internecine fighting among males to hoard as many women as they can. And so all the men of the empire could be turned into fighters to use against external enemies. Then, if the state takes care of enforcing monogamy, soldiers can embark in a long campaign in remote lands knowing that, at least theoretically, their wives will be waiting for them. The Romans, the paradigmatic military society in history, were strictly monogamous, at least with respect to the marriage of free Roman citizens. That was typical for most empires in history.

Monogamy may be one of the main reasons for the development of the emphatic mind we all have. If you live in a relatively egalitarian society, you have a large number of potential partners: choosing the best one becomes a difficult game that requires sophisticated empathic capabilities in order to convince a perspective mate that one is the right partner for him/her. It is a game where you have to deploy all sorts of strategic skills to optimize your chances. And it is a risky game: you may not be able to find the right partner or you may need to settle for a less-than-perfect partner. You may know the story of the man who had decided he would never marry until he could find the perfect woman. And after much searching, he found her. The problem was that she was looking for the perfect man! 

So, you see how difficult the game is, and you probably experienced that yourself. For sure, bronze age people wouldn't do too well at it. Imagine a bronze age warrior walking into a modern ballroom. He would stand in front of a girl and state, flatly, "I have plenty of sheep and you are to be my woman." Not exactly the best strategy to win the hearth of the prom queen.   

Then, of course, monogamy was never perfect and it was always accompanied by the activities that we call "philandering" for males. For females, we use terms such as strumpet, harlot, trollop, slut, or whatever. It doesn't matter, it is still the same game and it requires empathy. Married men are easily convinced by women who woo them, while married women have sophisticated ways to let men understand that they are happy to be wooed. But no modern woman would be interested in an affair with a bronze age man, no matter how many sheep he has. And no bronze age woman would be interested in an affair with a man who doesn't have any sheep. Empathy rules the game, that much is certain.

So, we can explain why the Western civilization has developed so many examples of what we call today "romantic fiction," from the saga of King Arthur, to modern telenovelas. It is probably a form of training for young minds that emphasizes such feelings as romantic love and typically involves a couple of lovers who face all kinds of obstacles but who, eventually, are reunited all thanks to being faithful lovers. This kind of fiction would be most likely totally incomprehensible by our ancestors. Imagine asking Tamar (the one of the Genesis) "but do you love your husband?" I can see her face looking like if you had asked her, "do you like French cuisine?" Some people have tried to cast Tamar in the role of a modern character with results, well, lets say not completely satisfactory (more details at this link).

 

The Final Question: How about the future of the mind?

After a few thousand years of prevalence, monogamy is clearly in decline. It never was perfect but, once, it was enforced by law and customs and, in some countries, you can still be stoned for being an adulteress. Even divorce used to be illegal in many Catholic countries up to recent times. Today, these rules have mostly disappeared, although 19 US states still define adultery as a crime and there exist two countries in the world where divorce remains illegal, the Philippines and the Vatican. 

This relaxation of the monogamy rule can be explained as the result of the decline of the role of males as fighters. Up to a certain time, not many decades ago, wars were won by the state that could line up the largest number of poor clods in uniform and have them march forward while being shelled by the enemy artillery. That's not so important anymore and the development of drones and war-robots has made the very concept of "soldier" obsolete.

The current situation is basically unheard of in the history of humankind. There has never been an age in which males had become useless as military machines. This point may not have been understood by the leaders, yet, but it seems clear that, if there is little or no need males as soldiers, there is little or no reason to enforce rigid codes and laws on sexual behavior for them and their wives

That's rapidly modifying the standard way of thinking about sexual codes of conduct, especially in the West, even though we can probably rule out that it is modifying the human genetic code (yet). In any case, the current way of thinking of Westerners is as far away as that of bronze age warriors as it could be. The focus on mind-reading is being turned to one's own mind and modern Westerners can be defined as extreme cases of narcissists, interested only in their own well being. It is what we call the "me-generation."

The problem with the me-generation is that it is generating a class of people who think they can do everything that pleases them. And the only thing that's worse than a narcissist is a rich narcissist. One of the things human males like to do is to hoard women in personal harems, as it was the use in some societies in the past. So, if a male is both a narcissist and he has enough power in the form of money, what can stop him from having multiple female partners in the form of occasional or stable concubines, or even in the form of a traditional harem? 

The current laws and customs prevent the men in the most visible positions from explicitly expressing their sexual habits, but if you look at the recent sex-scandal involving Jeffrey Epstein, you can notice that there are things going on with our leaders that don't appear in the media. Even without concubines or harems, already now, we might say that in the West the elites enjoy "time-dependent polygamy," in the sense that they periodically switch from an older wife to a younger one. That, of course, deprives young and poor males of suitable female partners, but it is the law of money. In time, we might see the development of a rigidly stratified society where the elites accumulate women just like they accumulate money. 

Then, if women are seen as accumulated capital, there follows that methods are needed to make sure that they are not stolen or lost. Eunuchs are a traditional way to keep women in their place -- and they also help solving the problem of excess males. But there are even more invasive methods to control women. Several societies in our time practice "female genital mutilation." The idea is that if a woman feels pain during sex, she will be less interested in cheating her husband (or harem master). In its extreme form, infibulation, the woman is treated like a coffer that can be locked and unlocked at will. Female genital mutilation is not so popular nowadays in the West but, who knows? Fashions change so rapidly!

Chances are that someone who owns a harem of infibulated women doesn't think of them in terms of romantic love, not any more than one of our billionaires have romantic feelings for their stock portfolio. Indeed, it is often reported that the rich are nasty, unfeeling, and uncaring for others. That's what you would expect. Why would the rich need to care for others? They don't need empathy-based skills. Then, the women in a harem would hardly be thinking of their master as someone to love in romantic terms. To say nothing about the eunuchs. 

So, if these habits were to become the rule in the future, then the human mind could change, culturally and perhaps even genetically. Evolution, cultural and genetic, does it work of eliminating those features that are not needed, think of the wings of the dodo bird. So, the sophisticated empathy capabilities that we had developed over the past 2-3 thousand years could disappear in a few centuries. Then, future scientists may discover a second bottleneck in the human Y-Chromosome diversity and wonder what caused it.

But there are other possibilities and it is not farfetched to think that the next step for society will be to discover that the modern obnoxious alpha-males and their manic sex-habits are not only useless, but expensive and dangerous. So why don't we just get rid of most of the males, leaving around just the tiny number needed for reproduction? After all, it is a choice that ants and bees made millions of years ago. Their social organization is called "eusociality" and human society already has some of its characteristics, so that it can be defined as "ultrasocial".

Is it possible to transform human society in such a radical way? Why not? We evolved, and we keep evolving. Already, the features of our society would be completely unrecognizable to someone living just a few centuries ago. And if ants and bees (and also the naked mole rat) evolved toward eusociality, there is no reason to think that we can't follow the same steps. Nate Hagens has been discussing how our society is already moving toward what he calls the "superorganism" -- a term used also for anthills and beehives.

Our society is already much more complex than the patrilinear demes of the Bronze Age and a future eusocial version would be even more complex. In the network of complex subsystems we live in, and in those in which we may live in the future, empathy deals with many more things than just finding a sex-mate. As Chuck Pezeshki notes, empathy is not a rigid concept, it is a process that evolves toward more complex and sophisticated forms (this figure is from Pezeshki's blog).

So, humans might be moving toward a version of empathy that will be highly sophisticated and structured as it can be in a universe that we are perceiving as more and more complex, a hierarchy of systems that we call "holobionts" and that culminates on this planet with the highest level holobiont of all, the entity we call sometimes "Gaia." Developing this kind of empathy could place humans truly in harmony with nature and with their own species. It would be a form of empathy that we can imagine as connected to what we call today the "religious experience." And maybe they'll perceive things that current humans cannot even imagine. It would be the "revelation through evolution," a concept that Michael Dowd has perceived. The Goddess Gaia revealing herself in her full glory,

And onward we go, evolving all the time. 


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h/t Michael Dowd, Chuck Pezeshki, Nate Hagens, Maria Mercedes Sanchez, and Helga Ingeborg Vierich,




Thursday, September 3, 2020

What makes us holobionts: Touching each other as a gift of love.

Image from Nella Turkki's dance project, "I, Holobiont"

 

Touching each other is part of what makes us fellow holobionts, part of the greater holobiont that we call the Ecosphere or, sometimes "Gaia." In his book, "Thank God for Evolution," Michael Dowd doesn't mention the term "holobiont," but he gives us a poignant description of what it means touching each other, starting at page 231

The Furry Li'l Mammal in each of us craves touch and tenderness. Without touch, a baby dies, the human heart aches, the soul withers. Touch is not only a biological need; it is a profoundly elegant and essential form of communication. . . . For millions of years our mammalian ancestors were reassured by parents or comrades not through words but through touch. For 99.9 percent of our mammalian journey, there were no words. The need for touch begins for mammals at birth and continues until we die. . . . There is healing in touch, too. Because tender touch communicates love and care, it triggers metabolic and chemical changes in the body that assist healing. Touching also stimulates the production of endorphines -- natural body hormones that control pain and embrace our sense of well-being.

And, let me add, touching each other means exchanging our skin microbiota: it means exchanging the skills that the small creatures that populate our skin use to protect us from harmful creatures and chemicals. Touching each other is a reciprocal gift, it is a gift of love.

Onward, fellow holobionts!  

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Below, you see the front cover of Michael Dowd's beautiful book "Thank God for evolution" (2008). But if you want to know why exactly ancient Christians used a fish as a symbol of their faith, you have to read the book by myself and Ilaria Perissi "The Empty Sea" (in Italian), or wait for the English version to be published by Springer (should be soon)

 

Monday, August 31, 2020

Cancer and holobionts: is there a link?

 

Image from Vyshenska et al, 2017


I have been studying the work on cancer of the Italian researcher Stefano Fais. You can find a recent review of his work at this link. Basically, Fais sees tumor cells as the result of an unbalanced metabolism that leads these cells to develop on their own, even using anoxic processes to grow. He maintains that it is possible to slow down the development of these cells by making their metabolic growth processes more difficult, in particular using proton pumps to make their local environment more basic. 

I am not expert enough to be able to give an informed judgement on these ideas. But, as you may imagine, it led me to consider if there were a link between cancer and the concept of holobionts and, yes, there is a line of research in this area. Several researchers seem to be exploring the idea that cancer is the result of a "dysbiosis," that is an unbalance of the host's microbiota. For instance, in a 2014 work by Apidianakis, we can read:

".... the host genetic background and that of the microbiome, define the intestinal hologenome, which is influenced by age and the environment toward homeostasis or disease. Thus, the intestinal disease may ensue when the intestinal hologenome is imbalanced, that is, when a genetically predisposed or old host interacts with its dysbiotic microbiota in an inadequate or harmful dietary or lifestyle-shaped environment."

The problem, here, is that there is no link whatsoever with Fais's idea that tumors are related to acidity. Maybe there is a link, somewhere, but the story is horribly complicated and I leave it here. It is just a note that you may find interesting and perhaps worth studying in depth.


Thursday, August 20, 2020

Genes, Demes, and Holobionts: What genetic studies tell us of the behavior of our ancestors

 

 Once you discover the concept of "holobiont," its ramifications keep surprising you. Here is a brief discussion of how the competition among the human meta-holobionts called demes affected and was affected by the human sexual behavior. 


How could it be that for a few thousand years only one human male out of about 20 females left descendants? What had happened that had removed so many males from the human gene pool? This is a story that would require an entire book to explain, but it is so fascinating that I thought I could write a quick survey, here. 

So, take a look at the image above. It is taken from a 2015 article by Karmin et al.  There is a lot of information in that figure, but let's concentrate on the left graph. It shows the degree of diversification of the human Y-chromosome over time. You know that the Y-chromosome is something that only males have in humans, so the curve is roughly proportional to the active male reproducing population. The more diversified it is, the more males there are around, reproducing. Be careful: this is not the total male population. It is the population of those males who reproduce. Males who never mate with a fertile female don't appear in the graph. Note also that females are tracked using their mitochondrial DNA that they inherit from their mothers.

As you can see, the population of reproducing males is always smaller than that of the females (right graph). That doesn't mean that the total number of males (reproducing + non-reproducing) is smaller than that of the females -- for all we know, these numbers have remained comparable over human history. It seems that human males always have more competition and more troubles to reproduce than females (if you are male, you understand what I mean). So a sizable number of males always disappear from the genetic history of the species, even though they did exist and maybe they were also sexually active. It is just that they left no descendants.

But the impressive feature of the male curve above is the dip that takes place between 7,000 to 5,000 years ago. Hard times for males: only about one reproducing males out of 20 reproducing females. Ouch! (or maybe not so much of an ouch for those who did reproduce, who had 20 females each). That's weird: how can that be?

As always, we should take into account that all scientific results are affected by uncertainty. But this work seems to be solid and so far it has not been challenged. So, the question is, what happened that made our female ancestors so selective in choosing just one male in 20 as the father of their children? 

You bet that a lot of hypothesis have been proposed to explain this catastrophe that hit human males in their reproductive success (but, again, it doesn't mean they didn't have female partners, just that they didn't mate with them when they were fertile). But what happened? An epidemics? The wrath of God? The spread of the fashion of monastic life? 

It is a long, long story and we are far from having understood this pattern. But I think that a 2018 paper by Zeng et al. gave the correct interpretation. It all has to do with demes.

One more paragraph, one more thing to learn: what the chuck is a "deme"? Well, it is a known concept in biology, although not so common for most of us. Basically, a deme is a relatively stable group of individuals who often mate within the group and rarely outside. In human terms, you may think of a deme as the equivalent of a "tribe" or a "clan." 

A characteristic of human demes is that they are often patrilinear: that is, they are dominated by a male hierarchy: there is a patriarch on top, his son, grandsons, and maybe great-grandsons. The females are more mobile. They practice exogamy, that is they tend to marry outside the deme (clan). The exchange of females among tribal groups is well known in anthropology. 

Now, you see here the holobiont emerging: a deme is a kind of a holobiont, we might call it a "meta-holobiont" in comparison to the normal human holobiont. But a holobiont is a holobiont is a holobiont. It is a group of organisms that collaborate in a symbiotic structure. Not just that, but demes practice "holobiont sex" by exchanging genetic material in the form of female organisms. See how many patterns tend to repeat? Wonderful!

Here goes the explanation by Zeng et al., that I think makes a lot of sense. As all holobionts, demes have a finite lifetime. They can die because of various natural reasons, starvation, disease, etc. Or they may be killed by aggressive neighborhood demes. And here is the trick. In a deme, there is very little differentiation in the Y-Chromosomes. The males are all related to each other and you know that brothers all have the same Y-Chromosome. So, the deme dies, the Y-chromosome dies. How sad! Those males who were part of that deme don't pass their Y-Chromosome to their descendants, so they disappear from the human genetic history. But so is the way things are. The great holobiont called Gaia loves life, but She knows that there cannot be life without death.

But the death of a deme doesn't mean the disappearance of the female genetic imprint. Not at all. Since females practice exogamy, likely, the females of a dead deme had sisters in other demes that survived. Besides, killing a deme in war doesn't mean that the winners exterminate all the females, not at all and for good reasons! Males consider the females as a war prize. Nowadays we tend to think that killing males and raping their females is not a very nice behavior, but it was very common in history (and still is). 

And here goes the final trick that explains the whole story. The drop in the reproducing male number takes place in a period of great expansion of the human population. It means that the demes were closer to each other and fighting for increasing scarce resources. It meant holobiont-style selection. Those demes that were less efficient in exploiting the available resources, and also less effective in war, disappeared, and with them a lot of Y-chromosome lineage. And that's what you see in the curve. Amazing!

But then, what happened that restored the chance of reproducing for human males? Well, there came the age of kingdoms, and then the age of empires, and kings and emperors don't like clans to fight against each other. They want all the males to fight for them, and that changed everything. Another long story that I'll tell in another post. But all these stories that deal with holobionts are fascinating! 

And here is how Conan the Barbarian interprets deme competition


 


Who

Ugo Bardi is a member of the Club of Rome, faculty member of the University of Florence, and the author of "Extracted" (Chelsea Green 2014), "The Seneca Effect" (Springer 2017), and Before the Collapse (Springer 2019)