Evolution, Language, Domestication, Symbolic Cognition, AI & Large Language Models | Terrence Deacon

About the Guest: Terrence Deacon, PhD is a Professor in the department of Anthropology at UC-Berkeley. He has written many papers and multiple books about the evolution of human language, origins of consciousness, and related topics.

Episode Summary: Nick and Dr. Deacon discuss various aspects of biological evolution, from natural vs. sexual selection to gene duplication and the consequences of domestication; the domestication of dogs and songbirds; human vs. non-human forms of vocal communication; ritual behavior & the origins symbolic cognition; artificial intelligence & large language models (LLMs); and more.

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Terrence Deacon 4:12

Oh, yes, I'm in the middle of a book called fouling up. How inverse Darwinism catalyzes evolution

Nick Jikomes 4:21

what is what is inverse Darwin Darwinism. So

Terrence Deacon 4:24

everybody asks, it's actually not anti Darwinism. It's a compliment to Darwinism. And I think it's a compliment that was there. In Darwin's own writing, though, he doesn't recognize it. And that's why I've used the phrase. So Darwinism in 1838. He came up with three ideas to send his chose up his notebook that basically drove the rest of his thinking. And it came up right after rereading or I don't know, they read the whole thing before this, but certainly reading Malthus on population this this whole problem Malthus realizes is that reproduction outpaces resource. And Malthus, of course, had this dire prediction that this would lead to terrible things in England in Europe. Because populations were growing so fast and resources were not growing fast enough. Darwin sees this and says, aha, but in the natural world, this is going to be the case. And that means there's going to be selection that favors a few over the others. Those that fit better with the contexts that can do better, they can outpace the others. And so this sort of drives his theory. And he comes up with three ideas, he says, the first thing is that I noticed that everybody realizes that the grandchildren are like grandparents, as basically they traits are inherited, they're passed on down. And he says, but but in fact, the second thing is that there is great variety and offspring. That is, although they carry some of those traits as a lot of variety. So that's a second story. That's a variation problem. Then the third one is, he says, But you know, then there's, there's great overproduction with respect to support of those offspring. And but those three things together, and you get natural selection. That's Darwin's basic idea. But notice that the Malthusian part isn't necessary. And it was what gave him the insight for natural selection. But if you think about things like gene duplication, that happens all the time in evolution, in fact, whole genome duplication does happen, particularly in plants. What happens is that the excess production doesn't necessarily mean that you're outstripping resources, doesn't take a lot of energy to produce extra genes, or to have a single gene that's duplicated, like in transpose on effect, there's not much energy use, but even in terms of multicellularity, think of the production of multiple cells, the reproduction by mitosis. Now, that builds a large multi cell body with maybe trillions of cells. There's some contexts in which some of those cells are in competition with each other, but not often. Usually, it's a context in which there's no competition, which is excess resources, in which overproduction is in fact, the way life has to work. In fact, to stay ahead of the second law of thermodynamics, you can't just repair things, you have to make extras, you have to have backups, you have to have duplicates, because something's gonna go wrong, eventually, we know that in terms of our own computer technology, that you got to have backups, you got to make copies of things. And that's how you keep things going. Well, evolution, of course works. But what happens when you don't have competition? When you don't have this subtractive effect, if you think about it, natural selection is a subtractive process. It requires variation. But it also requires overproduction. You have to make more than you need because you're gonna get rid of some.

Nick Jikomes 7:59

Yes, so you're taking away individuals who are unmatched to their environment, and leaving behind those that are better matched to their environment. But But I think I see where you're going here. If you think about something like gene duplication, that's not happening at all, you're just adding a new thing. And then that redundancy gives you space to evolve a new function without any actual competition there

Terrence Deacon 8:21

exactly are what it basically does is because there's redundancy, if one of them begins to degrade in some way, which will happen spontaneously. In fact, if you got two of them, then if one degrades, it won't be eliminated, unless it produces some troublesome project product. And one of the troublesome things that are going to happen if you've got to have something is that you can produce too much and too much can be a problem, I mean that we have a classic issue of that with respect to Trisomy 21, when the 21st chromosome is tripled, tripled, and said, Just dupe duplicated data produces Down syndrome. That is the overproduction of a bunch of genes is actually not such such a good thing. So oftentimes, when you over produce, it can also have negative consequences. So in fact, accumulating damage in the experts actually could be an advantage, you could decrease it. But the other thing is that you can also because damage on say one out of a few 100 nucleotides and the DNA molecule does a little bit a little bit of damage won't necessarily turn something completely off. It'll just kind of modify that function, oftentimes degrading it just a little bit. But there might be contexts in which a little bit of a change little bit of variation now actually complements what's already there. And so in effect, duplication, over duplication without elimination, allows enough redundancy that allows you to accumulate a little bit of variation and error without much cost.

Nick Jikomes 9:53

Yeah, and there's actually like, there's multiple ways this can go so for example, you know, gene duplication is relatively common, you get an extra copy of a gene, it's often not catastrophic. It can be, but it's often not catastrophic. And you can imagine, I mean, this, there's, there's examples of this that have been documented. You know, one way this could happen as you preserve the original function and Gene one, and Gene two just sort of goes in a new direction. But another way that you see sort of complexification evolve in the genome is what they call sub functionalisation. So that if you've got sort of two jobs that gene is doing, and then you duplicate it, it can be that gene one now just does job one, and Gene two just jumped to the now you've got the same functional outcome. But now you've got more complexity, more parts doing it, right. And

Terrence Deacon 10:40

that's the classic stories of those one is the hemoglobin gene, which is duplicated from myoglobin originally. And then the hemoglobin gene itself duplicates, and you've got an alpha and a beta. And they produce this, this tetramer, that now actually does a much more interesting job of carrying oxygen, because now you got four iron atoms, in this four part molecule, it's floating around your blood carries more oxygen, but also probably gets it off more easily to myoglobin in your tissues. But in addition, the beta hemoglobin duplicated a bunch of times, and now we have different hemoglobin through expressed at different times during gestation in the fetus. So that at times, because the fetal hemoglobin, of course needs to take oxygen from mother's hemoglobin, so it needs to have a slightly different oxygen affinity. But as a fetus grows, that difference in oxygen affinity needs to change as well. And when it's born, eventually, then you need to shift away from that because you know, the stronger your own hemoglobin holds on to oxygen, the more difficult it is to give it off to your tissues. So when you get when you're born, and you're getting oxygen easily just from the air, you now need to go back to a sort of a weaker hemoglobin, the standard beta. So this is a case in which it's duplicated many, many times. And in fact, the duplications all do different very different sub functions. One of them is within the tissue myoglobin, one within when the blood Oops, my my light went off, just turn my back on. And, and, and one has to do with a different timing in the lifespan. The other way that some functional sub functionalisation can work is of course, if rather than modifying the structural gene itself, modify the promoter in some way. So it's expressed a different time. Well, that's of course, the beta hemoglobins of that are duplicated into gamma and so on, in fetal life, different time in the in the lifespan, but you can also have it produced at a different part of the body, a different segment of the body. And, of course, that's what's happened with all the HOX genes that make up our body, that the same gene with a slight variation is now producing a different part of the body. And that different slight variation, now it can either produce, you know, very, very similar limb parts, like our fingers that are very similar to each other, or can produce very, very different structures, by virtue of now not being in competition with each other, but now actually complementing each other at a higher order level, that is a level of old body structures. So this, this process is one that occurs at many, many levels. And I've been focusing on all of those loans. Actually, the one that got me thinking about it originally had to do with the fact that we primates, need to eat vitamin C, we need to eat ascorbic acid and fruit, whereas almost no other mammal in fact, very few other animals in general need it. Because they have a gene that produces it, we actually have a pseudo gene, that somewhere back in our evolutionary past, we think somewhere greater than 50 million years ago, actually produce vitamin C and all primates, but the anthropoid primates and monkeys and apes lost this capacity. And, and they lost this capacity probably because they were eating fruit, and the fruit provided it from the outside world. So in effect, it masked natural selection on the gene and it allowed it to just pick up noise. So in fact, what we see now in most anthropoid primates is not only noise in the gene with lots of stop codons and the gene and so on, but in fact, is a major frameshift so that it's just complete nonsense now. And yet, that means that we're addicted to vitamin C, we have to eat it, we can't make it ourselves like like your dog or your cat can. So, as a result, a number of other things have happened, you know, we have changes in taste receptors, so that we actually have this pleasing interest in sweets and sour that is the acidic nature of vitamin C. But we also you know, subsequent to this the in, in monkeys and apes, duplicated the absence that is the the genes that are involved in producing light, receptive pay admits in a retina. And so the what amounted to the central pigment, a green sort of central frequency pigment duplicated got plugged right next to itself on the end of the X chromosome. And that one began to degrade. And as a result, it reduced its sensitivity to free to higher frequency became more and more red. In its reception. Now we have this sort of red green distinction, which of course, is critical to determine the ripeness of fruit, fruit is ripe, and you're giving a color signal to birds mostly. And initially, that says, Okay, now green, we were camouflaged, you can't see edible yet. But now I'm gonna make a clear change. And now you can eat me, well, that's a good thing to know, if you're a primate and you need fruit, you need to have this capacity. So one of things that happened here is that now a duplication outside the body. It's not just like a gene inside the body, but now it's outside the body created a whole bunch of other changes elsewhere in the in the body. So many genes are now contributing to the fact that we're getting enough vitamin C, getting enough ascorbic acid, we also have some, you know, blood borne molecules and so on that make it easier to take it in and pass along. A number of other adaptations responded now because we're, in a sense, codependent on something outside the body with duplication effect is both something inside and outside. And it's part of, it's going to play a role in, in all kinds of interactive effects, including social behaviors, the link with the outside or symbiotic, and commensal kind of behaviors that may be driving this or been driven by it. So a lot of these features, and what I'm interested in this new book, is to just go through the whole list fall from, you know, genes all the way up, I think, to even language, I mean, like, the classic example, where we depend on each other, you know, we have to be boring in the social group. So we're addicted to the social group, that's gonna do the same kind of thing that the vitamin C story would do.

Nick Jikomes 17:12

Yeah, I mean, there's multiple, there's multiple concepts that are that are important. So you know, to play with the vitamin C and the color vision example more. The basic idea here is, first, you have a lineage of primates that develops color vision, which is itself coming from an internal redundancy is happening spontaneously, you duplicate your opsin genes that encode our light sensitive proteins in our eyes. And now you can have this red green distinction, because you've got this syrup, you've got this extra gene that is now free to evolve. And what's interesting there is the redundancy is creating a context in which the novelty is actually coming from the relaxation of selection. So it's not just the subtractive process of taking away individuals who are not good at in a particular environment. But you've created this redundancy, the surplus, this extra gene in this case, and it's free to evolve, ie, I mean, what that really means is, there is no selection to maintain its existing function, because you've already got another backup copy. And then we're saying that ability, the color vision ability gives us the ability to detect ripeness of fruits and things. So now we've got external vitamin C, that we can readily find and adjust that then relax, it really does another relaxation of selection on our endogenous vitamin C production. And, you know, what's additionally interesting about this is once that relaxation of selection comes into play, and that endogenous vitamin C function gets mutated away. Right? There's, there's a sort of unit, you know, directional thing here, right? You can't, you can't undo that change. And so now you're really locked into, it's almost like creating more selective pressure for more novelty to evolve, because then you need to really, really make sure that you're never going to lose that ability to find the vitamin C in the external world.

Terrence Deacon 19:01

That's right. So you've got to have, you've got to like the flavor. You've got to have better abilities to move around in the trees. It's an open question whether the opsin duplication was before or after the degradation of the ascorbic acid Gene. Gene is called Gulo. For a complicated name, I won't go through it. But but that gene, we know we have a pretty good sense of when that duplicated and we're getting a pretty good sense of when we get I shouldn't say we get we had a pretty good sense of when that gene began to degrade. And by just comparing lots of different primates, and we have a reasonable sense of when the first duplication the opposite did in part because it turns out to be somewhat later. It turns out to be somewhat later because we see a different variant in older New World monkeys. And so it's clear that all the New World monkeys had already began to eat fruit and Become diurnal, their eyes get smaller, their teeth change in the fossil record. So it looks as though they're diurnal, which means they're probably already eating fruit at this point in time. But now we see that old New World monkeys separate. And it's not until the separation that we begin to see a slightly slight difference in how color vision is processed in all New World monkeys, Old World monkeys, like ourselves, were Old World monkeys in that sense, have this this three color vision all based upon one chromosome. And New World monkeys, it's across chromosomes. And so some New World monkeys, many New World monkeys are just die Chromat sanely, see in two colors are some by virtue of an interesting combination of their gene of their chromosomes become trichromatic. So it's an it's an interesting problem. And I think what we'll see, we begin to look at some of these other adaptations for ascorbic acid development, including the taste, taste changes, and so on, so forth, probably even changes in the teeth and locomotion and so on May may be involved as well.

Nick Jikomes 21:04

Yeah. But yeah, I mean, so it's just like, an essence, like a single, in this case, metabolic shift to losing the ability to produce vitamin C internally, it basically creates strong selective pressure that's going to be distributed across many different adaptations, right, you have to be able to detect fruits, by sight or other means, you have to be naturally interested in finding those things, you have to have the motor capabilities of obtaining them, and so on and so forth. And I think you know, where we're going with this, because there's probably something similar happening in language, the story of language evolution, but I want to talk a little bit more about some basic evolutionary concepts so that people have the proper toolkit. To that point, one of the things I want to get you talking about is, we can assume you know, this audience, you know, I've had many podcast episodes with with you and others on some of these subjects, you know, what we'll assume people know the basics of natural versus sexual selection. But I want to ask you about when these things come into conflict, so cases where an adaptation is favored by the opposite sex, and yet it makes it harder for an individual to survive in its physical environment? What are some examples of that? And why on earth would that conflict ever arise to begin with, right,

Terrence Deacon 22:22

that probably the best example of this is, with what are called widow birds in Africa, the widow bird is the male has an incredibly long tail. And during when it's displaying, and the mating season, basically flies low to the ground with a weird kind of slight slight that caused it to sort of go low and almost touch the ground and then come back up and fix the ground and come back up. But having a long tail means that that drags close to the ground means that you're probably pretty easily picked off by a predator under those circumstances. Now, it turns out that if, and this is sometimes called the handicap principle, that is basically these guys are actually risking their lives to display the females, because they have these incredibly long tails. But if a, if a number of males are out there, and many of them get picked off by predators, but one does not. And he's taking risks, then, if a female chooses that male to mate with, it's likely that that male is more healthy than the others more sophisticated in their flight, maybe has less susceptibility to disease, and so on, there are certain advantages that the female and her offspring will get from that process by picking a male who has survived despite these so called handicaps. The male on the other hand, that can actually survive under these circumstances, is also likely to have many more offspring. So it's an advantage for both males and females. Even though even though probably 80% of the males don't make it, most get picked off. One of the experiments that was done years ago, I can't right now remember the names of the experimenters but they basically clip the tails off of some individuals, and use super glue to attach that to other individuals. So some individuals had absolutely longer tails, and some individuals had shorter tail. So of course, that's going to correspond to the different predator effects. And they're going to be predict preyed on differently, but it turns out to the females prefer the individuals with extra super long tails. Now, what that would suggest is that although over time those guys will be probably be picked off and wouldn't make it at least for a brief period of time. Females don't have any limit on how long the tail ought to be. The longer the tail, the better looks like for them. Um, In part, because over time, there's going to be a balance at some point in time, as tails elongate in Burr in these male birds, it's going to be a trade off. So that a certain length of time, the amount, the risk you take of being preyed, and never reproducing. Compared to the advantage you have of maybe producing a lot of offspring, there's going to balance out so that natural selection, when effect set an upper limit on the length of tails. And, interestingly enough, does not change that for females. The Why wouldn't it change it for females. But ultimately, it's a pretty straightforward story. If the environment changes are fewer predators, better better for females to choose the longest tail, even if it's way longer than normal? So there's no real limit on female choice here, let's go to limit what females think is the optimal tail length. But there's going to be an optimal tail length set up by the environment. By virtue of you know, what's the probability of a male surviving with a long tail. So there's a case in which sexual selection which is driving this choice of males by females, and natural selection, which is setting an upper limit, so to speak on the length the tails, actually, you're setting up a balance, and what will happen is it will run to the point. So if you are predators in the environment, for example, we should expect that tail feather length should get longer. If there's more predators in the environment, we should expect that tail feather length in males will be shorter. So that to some extent, this balance between sexual selection and natural selection will actually be very useful in sort of fine tuning to the environment.

Nick Jikomes 26:41

And so I suppose that would imply that as selection pressure in the survival sense, gets lessened. So for example, if a species somehow finds itself in an environment that's less dangerous, there's less predators, you would expect male phenotypes to start to become more and more driven by meat, just raw meat preference rather than survival value. In other words, sexual selection will sort of beat natural selection in that sense,

Terrence Deacon 27:10

to the point that it hits this upper wall, it will be able to go forever.

Nick Jikomes 27:17

And I mean, what's interesting about that is, you know, when you start to think about our own species, right, we've we've created social structures that have eventually allowed us to create societies where the environment is not as consequential for us as it was when we were more primitive hominids walking around with with saber toothed tigers, you know, hunting us. In other words, we've removed some of that, select that natural selective survival pressure. And so the expectation would be that more and more of human male phenotypes over evolutionary time in our lineage should be more strongly. They're being pushed by natural sexual selection more than natural selection.

Terrence Deacon 27:57

And yet, the major predators on humans are humans. So this is going to change the balance in a different way. What it says is that cooperation may be the safest thing to be to be a cooperator. But to be fearful of others, some strange others, but via a very strong cooperator within your familiar group, these things might be an advantage. So there, there will now be a sort of different balance, different features will be unbalanced, and will be shoved one way or another. And, of course, to be a good cooperator. As a human being, you also need to be able to communicate well, you need to be able to tolerate the variation of your close relatives. And you need to some extent, cooperate, succumb to the the group's ideas, you maybe even need to sort of, you know, follow along, to stay in a large stable social group. So there are going to be a number of things simply because to acquire language, to avoid intergroup predation, so to speak, there gonna be a lot of very different features at work. Now, the troublesome thing is that as technology develops, of course, it's going to it changes the environment, it's going to amplify certain things, and damp others. Now, I don't know, I would guess that in the amount of time that significant technological developments, including, you know, weapons of war, beasts of burden, and so on, and excess resources and so on, there's going to be fairly recent in human evolution history, and probably not a lot of natural selection has been at work. I think that's probably a good thing, because it would have driven us I think, in even more extreme directions. Nevertheless, I think those biases that were already there can be easily amplified by the environment and the sake. And so I would guess that the last, you know, 510 1000 years of human prehistory has been a case in which those biases have been significantly driven, although I don't think it's made a big difference at the, you might say genetic, neurological level.

Nick Jikomes 30:08

You know, another. Another area that's very interesting is when we think about Darwinian processes that are happening within individual organisms over the course of development, and you know, this concept of redundancy comes back into play, but in a kind of a different interesting way. So, for example, you know, when we talk about things like gene duplication, these are stochastic molecular events that just sort of randomly come up with some frequency, but baked into the developmental process itself. In particular, the development of the brain is this sort of, you know, intentional, quote, unquote, over overproduction of synapses. And it's actually a feature of brain development, that you produce an excess, and then you, you take away that excess early in development. So can you talk about those kinds of competitive Darwinian interactions that our neurons display as we're developing? And why why things would be set up that way?

Terrence Deacon 31:02

Right. Now, that's a very interesting issue, because obviously, you're seeing both happen you're seeing is overproduction you're seeing remember that one thing is going to happen is that brains are going to be different in different species for different reasons. You know, a classic example is, as primates, both of our eyes face forward, but if you're, you know, a prey animal, you want to have more 360 degree vision. So you want your eyes to the side, there's certain things you have to give up to do that. But the question is, what with different positions of the eyes? Do you need to have mutations in the nervous system that say, okay, you know, your eyes are this far apart, in order to make it work, I've got to, you know, I gotta have this gene change. Well, in fact, even among primates, and among our own species, there's a lot of differences between the width of our eyes. One of the ways of, basically having a nervous system that doesn't have to sort of with each subtle changes in the periphery to change genes, you know, are going to revolve changes in connections in the end in sight, one way to do it, is to have the development of the nervous system, adapt to the body itself. So if you think about the Darwinian story, think, you know, think about the body as the environment, how is the brain can adjust to a variable body? Well, the answer is, it's going to work like natural selection does, you're going to generate connect extra connections, you're going to allow both options to take place, both all possibilities of eye position, for example, might work. But then you've got to use the relationship between the periphery, the input of the eyes, and the competition, now set up between synapses to organize vision in a way that matches the outside. So in many respects, embryonic development, and at many levels, including extra limbs, extra fingers, and so on people that are born with a sixth finger, for example, usually, it's a working finger. That's because the nervous system has said, okay, you know, it's developing in a way that has anticipated How many fingers you're going to have. It's not

Nick Jikomes 33:13

all pre specified, not pre specified, which is actually a huge feature, right? Cuz then you don't have to encode all of the detail in the genome. That's

Terrence Deacon 33:19

right. So, but this, what it does mean is that now epigenetic effects are going to be much more powerful. That's going to have to be important at many, many levels, once you allow epigenetic effects, that means also, the environment can begin to have more of an effect on the ultimate phenotype. And with the nervous system, we certainly know that if you if you damage peripheral systems in some way, you can actually change radically changed maps in the central nervous system. So and that's because it's responsive to this. But now, here's the other piece is that, you know, we have quite large brains for primates. How is this competition going to be modified? How's it going to be affected, we don't oftentimes think about the story of brain evolution in our own species, as an EVO Devo effect that is in which evolution has been affected by developmental effects. But clearly, the wiring of the brain since our brains are much larger in a smaller body, the wiring is going to be different because this the the Darwinian like effects are going to be modified. And I think about this sort of like I think about gerrymandering in elections, you know, we we shift the balance in some way or another, and you actually change the consequences that give some a better chance at competing and make others less likely to compete. Well, competition is driven in part by a phrase that's commonly used is that neurons that fire together wire together. Well, if you've got more of them in a certain place, they're going to have an advantage. They're going to have a gerrymandered advantage of taking over more space in the nervous system. Yeah,

Nick Jikomes 34:58

and Yeah, so you can essentially get get more votes by creating more neurons or altering the ratio of connections from one place to the other. But to illustrate this, I think I think a good example, and you can probably give many of this is this idea of, of natural selection and competition between neurons and from different parts of the brain. When you deprive someone of like one sensory modality, one part of their brain that we think of as being visual, or auditory, or whatever, can be taken over by another modality, are there some examples of that, that illustrate this, this competitive process

Terrence Deacon 35:31

in a brain as large as ours, it doesn't really have that kind of a massive effect. Even congenitally like people who are, don't really have a lot of auditory responsiveness in visual areas, for example. But a smaller brain, where distances are not so huge like in rats and mice, there's significant changes in the mapping structure that can take place. Probably the best studied in classic example, has to do with whiskers, the what we call fight Bresee, the faces of cats and mice and rats and so on these long, you might say extra thick, extra strong whiskers that stick out. It turns out that if you look in the part of the cerebral cortex, that is the map of what you might call tactile space of the body, there's actually a very precise map of whisker positions, you can actually stay in the brain of these animals after after birth and after death, and look at a very precise map that looks like a kind of a checkerboard of places that each response correspond to a whisker position. But in early life, you take a young rat or mouse and you clip out some of these whiskers, the map will be different. The map, the existing whiskers, will, in a sense have taken over the space of the missing whiskers on the map. So the map actually is now corresponding to the body, we also find this in the case of congenitally deaf mice, for example, you can see that, you know, because of the genetic effect, maybe disturbing the cornea, the cochlea of the auditory system, what can happen is that you see a shift in which visual and tactile areas have taken over some of the auditory areas, not completely, but basically disturbs that map in the human brain. And I would say, in most primate brains, because they're fairly large, that kind of competition for space is probably slightly different, it can't take over quite such a large area. So I suspect that it's minimized as brains get bigger. On the other hand, with the enlargement of brains, what we're seeing is a sort of functional version of what we were just describing in terms of redundancy by virtue, like gene duplication, for example. Now, if I have input going to the same area, but it's twice as large, I only, I may only need half of that, or a fraction of it, or, or I might only need to use some of the cells in it for the original function, and there can now be a relaxation effect that allows more differentiation and function in a larger brain. So I do think that there is an effect that's analogous to this in brain development. And it's partially because it has this two sides. It has, I like to use this old this phrase, you know, all work and no play makes Jack a dull boy, well, you know, all selection, and no variation and no overproduction. No relaxation, makes evolution dull, it can do as much, you really need to have this sort of freedom to produce variation, that's not a problem. And so it shouldn't surprise us that play in animals with complicated brains might also play a very significant role like this. That is, this is something we've ignored, because we think of complexity and, and greater capacity is always requiring work. And, and you know, you got to select on it, and you got to get rid of things and hone things in, we tend not to focus either on whether it's just a cultural thing, or just the history of the field, we tend not to focus on the play side of it much. And we mostly just talk about it in terms of variation. Well, it's not just variation, its tolerance to variation, that that that allows you to explore, just as play in, you know, in predators allows them to explore various means of playing with their prey or sneaking up on prey and so on. It's an exploration. So I think this is that's why I call it an evolutionary catalyst. Yeah. Makes it more likely that certain things will happen.

Nick Jikomes 39:53

Yeah, I mean, I think what you're saying is literate. So you've got built in redundancy and this over auction, that's just an intrinsic feature of the system of how brains develop, quite literally, play represents a different pattern of walking through a neural space. And a different pattern of exploring that space is going to give you a different selection pattern, which is going to, you know, it's ultimately going to give you a different set of features than you would if you were solely focused on survival. And you were quote, unquote, working in your environment all the time.

Terrence Deacon 40:26

Right? Well, and, and if you think about it, play in mammals, in general, is the context of relaxed selection, you make mistakes, you're allowed to make lots of mistakes, you don't even have to work with the real thing, you know, just with with effigies of prey, you know, I can be a cat chasing a ball of yarn, and practice, in effect, not because I'm practicing, being a killer. You know, it's just fun. And so part of it also has to do with, you might say, selection for having fun. And I think part of what we describe oftentimes isn't the knee in our sort of childlike like, you know, the way we like to play like we're playing with ideas now is in part just because we've got the capacity to do that. And that actually is an advantage, because it exposes lots of opportunities that we wouldn't have discovered before this, it allows us to combine things in unique ways. And of course, we human beings have, I've done this extraordinarily well. Once we've developed linguistic capacities, and our technologies and so on, it allows us to sort of offload all of this play also on to other things that we love to do. Including, you might say, the arts, the arts are an example of play.

Nick Jikomes 41:53

One of the, you know, one of the things that's, you know, the areas that that you've explored in some of your writing that I thought was very interesting, is domestication, and how domestication really ties into a lot of the things we've been talking about around relaxation or reorganization of selective pressures. You know, oftentimes, when we talk about domestication, we think of humans domesticating other animals like farm animals, and of course, right, if you're building a barn and the fence and making sure the wolves never get too close, you're relaxing the selective pressures in the environment that these prey animals would otherwise be exposed to. And therefore, they're going to evolve in different ways they would not have otherwise evolved. But we've also, as you've pointed out, and others have pointed out, we are also a self domesticated species. And that's also very interesting and important to think about. So just starting with the basics here, how exactly as sort of an evolutionary biologist, defining it in terms of selective pressures and constraints and relaxation of selection? What exactly is domestication?

Terrence Deacon 42:54

The problem is that domestication is many things. And we have one word for it. Clearly, we have domesticated species. That is, we've not imposed selection so much. In terms of the outside world, but we've selected we selected for animals that can work to get to can hang out together in large groups without fighting and competing. Therefore, we have to select against population stress effects, we have to select against aggressivity. And if we're going to have a bunch of them together that we're going to raise, we, as breeders select those, and as we select various traits in dogs, and so on, we're doing the selection, that's active. domestication. Clearly, that's that's going on with lots of human domesticated animals. And of course, plants, we select for certain features in plants by simply allowing some to reproduce more effectively, and others to not reproduce. So we're playing this role, the role that actually got Darwin thinking about this in the first place. That's why I call it selection. selective breeding is playing a role in this. And so the question is now for different species, what's being actively selected in terms of selective breeding, well, clearly reducing aggression. We even go farther further than this in particular, in a herd animals, where males might typically be competing and fighting with each other, and actually injuring each other in competition for mates and for controlling large groups of animals. We very often neuter the males, so they never get to that stage and so they can now actually stay in the large social group without being very aggressive and about being damaging. And yet we've also selected for more stress tolerance, because being in a large social group, and being confined may be stress So, but so we select for this and what we see, when we look at a lot of these domesticated species, when we say domesticated, typically, we mean by humans, domestic, of course refers to being in the home, you know, so basically hanging around us, we're gonna see that there's many of these features that are characteristic that we would want to make possible. So the human beings have played a significant role in this. And as a result, domestication in animals or going to eat actually produces changes in their bodies, in the same way that domestication of food crops has amplified, those parts that we will eat that will be editable, as opposed to those not, those are very distinctive, you might say, in enforced or human selected domestication. But then there's domestication in other ways. And we now think that dogs for example, self domesticated, those wolves, self domesticated to become domestic dogs, in part because they also needed to be able to find this wonderful resource, we provide garbage piles, you know, we things that we can't eat, that are still edible, if you got the right kind of digestive system and, and, and masticatory system that you can maybe crack into the bones, you can chew these things and, and get food that human beings would not want to keep. But that meant that that wolves that were more tolerant of each other in large groups around these, but actually do better that is they are better in social groups that were not so aggressive, that would be willing to hang out hang around human environments that might otherwise be stressful and dangerous, and might not be a threat to people so that people wouldn't go after them. They're going to self domesticate in order to gain access to this. But then human beings can then of course, take advantage of some of the things that they do well, which is finding prey, and so on, and so forth. So a first stage of self domestication leads to humans controlling domestication in dogs so that we get a really complicated interaction here. So the dogs in a sound self domesticated in order to be able to take advantage of a resource. We can say the same thing about humans. Now, what was the resource that we had to take advantage of? Well, certainly, in the savanna of our very early evolution, probably close to 3 million years ago, there was a lot of animals that have been preyed upon typically large bobbins, and so on, on the, on the fields and savannahs of Africa. The one thing that the predators couldn't do is they didn't have Jaws strong enough to break the largest long bones of big Barbets. In other words, the sort of the fevers and so on these these huge, very, very dense bones, and you know, dogs chew on them, but they never break through them unless you break them up and cut them up, so they can get the marrow. But I suspect that our ancestors for a long time, were using stones and things to crack open nuts. We already had, I think, probably maybe going back almost 4 million years, we probably had this capacity to crack things open. And so I don't think it would have been much of a stretch for our early ancestors to be into crack, figured that they can go in after the predators and scavengers had finished their jobs and still find food, their bones, but they had to do so now in a very different context. To do so in a context in which exposing themselves to predators out in the open savanna. That meant you had to have a cooperation, somebody had to keep the predators away while you're Did you hit your head down, chopping on this, this bone, maybe cracking a stone, so it became sharp, and realizing that the sharp edge could also scrape off some of the meat, you can now go in there a little earlier, but you know, really had to chase off the predators. But now you have a situation in which this is wonderful resource available. But you have to be able to work as a group, the competition between you has to be reduced, because you're trusting somebody to keep the predators away while you're getting the food. And the guys that are keeping the predators away, you have to trust that you're going to share that food. At some point, when you get back and climb up a tree where you're safe.

Nick Jikomes 49:33

You obviously need to be able to communicate with a certain level of sophistication.

Terrence Deacon 49:38

Right to Know who's doing what, when and to know that it's reliable. So all of this, I think sets us in a situation a little bit like the dog situation in which there is this wonderful source of nutrients out there. That's not available to anybody else. And then if you have the right tools and the right social organization, you can get to it, but it's going to select for all this that's going to select for many of the things that are selected for in normal domestication as a change in stress response and ability to handle being in large mixed groups possibly reduction in competition, possibly competition over females. And it might select for a form of communication that made it easier to do that. It's what I think language does, it allows us to communicate about the past the future promises, expectations, and so on, in a way that other kinds of communication does not. I think that had to be a very early stage in this process, and probably, I think, probably took a couple of million years to develop to the level we have. Now, that's a very, it's a very long term process. But in effect, I think it begins with a kind of self domestication. And of course, if you think about language itself, it already requires that you're in a social group, you can't get it unless you're in a social group, you can't get it unless you're in a social group that can survive over generations, because language has to be passed on and developed socially over a long period of time. It's not something that just develops in a few years or even a lifetime. So that's sort of a prerequisite. And I would guess that socialization and language sophistication probably co evolved over a long period of time, one pulling the other along, that being part of a very unique kind of domestication, that that we were involved in. But in this case, it's us. It's a self domestication story, all the way through.

Nick Jikomes 51:31

Yeah, I mean, one of the pieces that's fascinating there is, I mean, there's multiple threads, you could tie into this. But one of them that salient to me is, if you look at the metabolic and digestive adaptations human beings have compared to other animals, and you just sort of say, what does our metabolism digestion look like? Does it look the most doesn't look like a herbivore like a cow? Not really? Does it look like a carnivore? Does it look like this, that or the other? And the answer in terms of things like stomach pH and various other features of our GI tract is we have similar digestive systems to scavengers, particular meat scavengers. And that's basically ties into the story that you are telling them. I think others have told that a key piece of early human evolution, and I'm not sure how much explicit evidence there is for this, is that we were basically power scavengers, who could not only organize ourselves to ward off, you know, big scary carnivores who made kills. But we could take advantage of these food sources that gave us and once we could do that, they were not only food sources, but they're very, very nutrient dense, which maybe even helped unlock future brain evolution, basically,

Terrence Deacon 52:42

I don't have a lot of faith in that we needed food of a special sort to build big brains, there's a lot of theories like that, I actually don't think so much of a driver. It's a sort of, you know, if you've got it, then you can build it. I think it probably works the other way around. My suspicion is that that brain size may have evolved, in part because of a better food source. But we do know that that that human vegetarians and and people that don't get a lot of seafood and so on, don't have a lot of the particular kinds of lipids that are necessary for building the myelin of brains still have pretty normal brains and large sized brains. I don't think we have a lot of metabolic evidence that there is a the metabolism made brains possible. But this is an empirical question. And we'll find out as we begin to pursue this. And we'll know in part because of the genetics of it, as we learn more about the genetics, for for converting tissue, I mean, converting nutrients into neural, neurological tissue, how it's done, under circumstances of extremes. All of this will, I think, help us understand it, but we'll be