Ep 7: Genes Don't Do Crap (with Massimo Pigliucci)
What is the connection between an organism's genes and its environment? Can the environment alter an organism's characteristics without altering its genetics? Can an organism alter its environment and change the course of its own evolution?
Tune into this podcast to hear Marty and Art talk to Massimo Pigliucci, a professor of philosophy at CUNY-City College in New York, about how the environment can alter an organism's physical characteristics without altering its genetics, and how our ability to alter our physical environment may have altered the course of human evolution.
Massimo began his career as an evolutionary biologist, and has published numerous scientific and philosophical journal articles and over 10 different books.
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AW = Art Woods
MM = Marty Martin
MP = Massimo Pigliucci
00:04
MM: Today we're talking with Massimo Pigliucci, the K.D. Irani Professor of Philosophy at the City College of New York. Before becoming a full-time philosopher, Massimo worked as an evolutionary biologist, and then, as now, he's a strong voice for updating the foundations of evolutionary biology, but we'll hear why later.
AW: When we asked Massimo for his five big ideas in evolutionary biology, he gave us this group: natural selection, phenotypic plasticity, epigenetic inheritance, evolvability, and niche construction. That's a big and exciting set of ideas, and there was simply no way we'd cover all of them in our chat, but we'll get to them in future episodes.
MM: In this episode, we talk with him about phenotypic plasticity and niche construction. Plasticity describes how different genotypes produce different traits depending on the environment. Although this might not sound controversial, plasticity had led to some major rethinking about how evolution works and has led some biologists to claim that genes are followers in evolution, not the leaders they're usually thought to be.
AW: Niche construction describes how organisms modify their local environments. Think beaver dams. The idea of niche construction has reverberated through the field of evolution and has recently motivated biologists to ask whether niche construction by humans and other species can change the course of their own evolution.
MM: This podcast is a full length recording of our conversation with Massimo, but if you want to hear a shorter version, you can get it on our website, bigbiology.org, or wherever else you get your podcasts. Now, let's dive in! Welcome to Big Biology.
01:34
MM: We contacted you a couple of weeks ago I guess, and asked you to give us your big five ideas in evolution, and I, we did constrain you to five, you might have wanted to give us twenty, but five was all we asked, and today we probably won't even be able to get into those five, but, so let me set the table there before we get started and jump into any details. Your five, and correct me if I've got them wrong, were natural selection, phenotypic plasticity, epigenetic inheritance, evolvability, and niche construction.
MP: Yep!
MM: So, I think before, we've chosen to talk about, just for the sake of time, we've chosen to talk about phenotypic plasticity, since it's so close to home, and niche construction, but before we talk about either one of those, I'd just like to hear why you picked those as big ideas, and I think generally what constitutes a big idea in biology specifically.
MP: Well, yeah that's a good question. So, those choices will reflect my own judgment. If you ask one of my former colleagues for instance at Stony Brook, Doug Futuyma (?), who is the author of still today the most wildly used graduate level texts in biology, evolutionary biology, he will probably not give you at least three of those. He would include, certainly would include natural selection, but I don't think he would think about plasticity, evolvability, niche construction, or genetic inheritance. In fact, he would basically give you just one of them. And there is a reason for that. So, Doug, I'm not picking on him, I mean he's a great guy and a great colleague, but he's just a very good example of what I'm about to say. So, there is a little bit of a split right now in evolutionary biology. There is a number of colleagues who are perfectly happy with what is called the modern synthesis. The modern synthesis is basically the standard model, you know the equivalent in biology of the standard model in physics. It was a theory, or a framework, it's not really a theory, it's a framework for thinking about evolution that was put together between the 1920s and the 1940s to solve very specific problems concerning, you know, that were affecting the original Darwinism for instance, reconciling the original Darwinian ideas with the discovery of Mendel's laws and you know, basically the rise of genetics. That has been the model that has been taught, it's still taught to most graduate level courses today. But over decades really, people started making or grumbling noises about the fact the modern synthesis wasn't wrong as much as it was a little too limited. It had for instance left entirely out certain fields of research, like developmental biology. Others, it had taken on, you know, kind of a perfunctory way, but not really, you know like ecology for instance. And then there is a bunch of other stuff that has come out and has become prominent in evolutionary studies over the last two or three decades, including the four things that I've mentioned that Doug wouldn't, that a certain number of people felt, is beginning to feel that, like okay, well, all of this stuff really doesn't fit into modern synthesis, we need some kind of expansion of the framework, and this is what is often referred to as the extended synthesis, or the extended evolutionary synthesis (EES). So, what I'm getting at, so my five choices are a reflection of the fact that I am a supporter, or one of the people that is pushing for, the extended synthesis, which is still I think, to be fair, a minoritarian view within the field, but I think that it is one that is actually getting strength and support, it's you know a lot of colleagues are now, especially young colleagues which is a good sign, young colleagues, grad students, and post docs, actually embracing the new framework, and they are doing a lot of research on those four areas that I was referring to other than natural selection, which is still the fundamental, arguably the most fundamental idea in evolutionary biology anyway. It's still there, nothing on that point of view, nothing has changed. This is not a paradigm shift, this is not a new theory or rejection of Darwinism, it's a significant expansion of what we had before.
05:58
AW: I wanted to jump in here, Massimo, and ask about just big ideas and biologists in general. So, do you think biologists are good at generating and testing big ideas in relation to scientists in other fields? I mean, you know, it feels like there's maybe a sort of more central, core set of big things that are under test in physics. There's obviously a lot of big ideas in biology, but you know, biologists in general, are we good at formulating these big ideas?
MP: Yeah, yeah that's a good question. I actually think they're better than physicists, and certainly better than anybody else, and of course I say that because I am an evolutionary biologist.
MM: Of course.
MP: No, so this is actually a good question, right, so testing the big ideas, how do you test big ideas, right? Because tests, usually empirical tests, are aimed especially in the so-called special sciences, and basically everything other than fundamental physics is a special science. So, biology, you know, evolutionary biology, ecology, molecular biology, genetics, you know, but also outside of biology, geology, chemistry, and all that. All of those are considered special sciences by the, by philosophers of science. The only one that doesn't fall into that category is fundamental physics. Now, in the special sciences typically, you don't test big hypotheses. Big hypotheses provide a framework, so you know, it doesn't make much sense for instance to say, well, let's test natural selection. I don't even know what that means. Natural selection is a phenomenon that we, a process that we think occurs in nature. We can document it because we can measure it indirectly, you know, there are certain techniques that measure, but testing natural selection is like weird, it's like saying, ah, well we should test gravity. Well, just go outside and throw a, throw something in the air and then you'll have that. You know, now what you want to test of course are your ideas about gravity or about natural selection, how they work, etcetera, etcetera. In that sense, the reason I said, a little bit provocatively, that evolutionary biologists are actually, or biologists in general are actually better, is because the physicists, especially recently, have run into trouble in terms of the limits of what they can test, right. So there is a huge debate going on in fundamental physics about supporters and critics of string theory, and the critics are now becoming more and more vociferous, and they're saying, "Hey guys, you've been around with this theory for 35 years and you haven't provided us, you know, empiricists, a single test of those ideas. You keep telling us that that's the next big thing in physics, but in fact you're sort of running out of opportunities to test it. Now you're beginning to tell us that in order to test it, the experimental apparatus would have to, would require levels of energy that are, you know, clearly way outside of anything that is foreseeable for human technology, so it's like, ah now what?"
08:49
AW: So, so the ideas have sort of outstripped the ability of the tools to provide the tests.
MP: Correct. Now, that's not necessarily the fault of the string theorists, right, they would say, "Well hey this is just the way it is, what else do you want from me," right? But it is a serious problem. I mean, so in fact if you notice there have been discussions the last two or three years, even major journals like Nature Magazine published a call by a couple physicists to sort of, to take back the fields from string theory and so on and so forth. So, it looks like at the moment at the least, fundamental physics is actually running into trouble. While on the other hand, biology, with very few exceptions, biologists have been able to test all of the major big ideas that they have come up with, even outside of evolutionary biology. So, one of the big ideas in biology outside of evolution, strictly speaking, is of course the double helix structure of DNA. Well that one was tested almost immediately. So, it seems like biologists have actually been fairly successful. One of the exceptions, probably the only exception I can think of at the moment, is the origin of life. Ideas about the origin of life are really difficult to test, for the simple reason that we don't really have a lot of information about what the conditions that led to the origin of life on Earth, you know three and a half billion years ago. Where? But outside of that, lots of big ideas in both molecular biology, genetics, and evolutionary biology and ecology are being tested all of the time, and so they're fairly successful fields.
10:18
MM: So that's interesting, so are you then saying that biologists have been more creative? Or more creative or just better able to test the hypotheses so the problem is more tractable? And the reason that I ask that is, you know, one of your favorite topics is the genotype-phenotype map, and that sort of continues to be one of the pretty difficult nuts to crack, so...
MP: No, yeah. I don't think that biologists are any more, any smarter or better at doing science than anybody else. Just like on the other hand I would immediately add, physicists are not, despite what many physicists themselves think, they're not smarter than anybody else. It's a question of, you know, it's a question of what the problems are and what the technology is. So, for instance, for a long time, developmental biologists really couldn't do much other than descriptive work. Okay, they were doing wonderful work, and they were doing, in the early part of the twentieth century and into the '80s, really, they were doing wonderful descriptive work, dissecting, you know, embryos at different stages of development and so on and so forth. But there was nothing they could do about uncovering the molecular mechanisms underlying developmental processes, because the technology was not there. And now, this has changed, and things have exploded in the 1980s, '90s, and currently there is an entire field called evo-devo, where people are making tremendous strides. So, no I don't think it's a question of people being smart or not, it's a question of what is the relationship between the theory and the empirical evidence, empirical practice, and has the empirical practice gotten to the point in terms of technology that allows, you know, significant tests of the hypothesis. Sometimes that's the case, sometimes that's not the case, and that kind of pretty much goes across fields, and sometimes people just have to wait until, and if, the technology develops, because you know, I'm not one of those people who thinks that any scientific question will necessarily have an answer one of these days. I mean, there's no reason to think that's the case. The human mind is limited, and human technology is limited, so maybe, maybe not. We'll see.
12:24
MM: So, at the mention of evo-devo, that probably is a good time to tackle the first one, phenotypic plasticity, and I guess before we go too far it would be useful if you could define it, maybe give a few examples too.
MP: Sure. So phenotypic plasticity is something that has actually been known from the beginning of the twentieth century, right shortly after the discovery, the rediscovery of Mendel's work, and therefore the beginning of genetics, modern genetics. People started talking about phenotypic plasticity. But it had been considered a sort of background issue. It's in fact, kind of noise to get rid of rather than a major player in evolutionary theory until fairly recently. So, let's first define it. So, plasticity is the ability of a genotype to produce different phenotypes in response to different environments. Now, as I said a minute ago, early, this phenomenon was actually discovered in 1909 I believe, by Johannsen, who was actually the guy who coined the terms phenotypes and genotypes to begin with. And he was working with Daphnia, these are you know unicellular organisms that live in ponds, and he discovered that if the Daphnia lives in ponds without a predator, without a significant predator present, then they develop into sort of the, in a, their head, so to speak, because as I said it's a simple microorganism. But let's just say the head is kind of spherical without any pointed parts. But if there are predators, it becomes pointy. And, right, and so the ideas is that that's adapted because it's an adapted type of plasticity because it protects, to some extent, the Daphnia from the predators. Now, phenomena like that have been discovered for the last century all over the place. They're very common, they're very, so cases that have adapted plasticity are very common. Now, however, until the, I would say, at least the 1970s included and probably early '80s, most evolutionary biologists would look at plasticity and say, "Yeah yeah yeah, we know that there is that sort of thing, but it's kind of noise. It's like something that happens that we can treat in the background. It's an exception more than a rule. It doesn't have much of a significance," and so on and so forth. And there is reasons for that. It's not because they were lazy, but because the dominant mathematical theory in evolutionary biology, which is population genetic theory, simply cannot handle plasticity. There is no way to put it into the equations, okay. It would require major rethinking of sort of, the mathematics underlying you know, our models of evolutionary theory. Then, beginning in the '80s and then even more so in the '90s and up until now, a number of people, including myself, that was what I did my PhD thesis at University of Connecticut, plasticity of species of weeds known as Arabdopsis thaliana, which is easy to work with. It's often, it grows very fast and it's very small. It's kind of often referred to as the fruit fly of botany. It's very convenient to use for genetic studies. And, so a number of people, including myself and my advisor at the University of Connecticut, Carl Schlichting, started making lots of noise about, look, we, you can't ignore this thing, because it's ubiquitous, it's everywhere. Every, almost every trait we look at in almost every natural population, no matter what species you're looking at, there is plasticity. So, what do you mean it's noise? It's not noise, it's a major thing. And then, at some point, in the late '80s, I think it was '89, Mary Jane West-Eberhard (?), who was a major player in sort of modern evolutionary biology, put out a huge review paper, essentially, not only pointing, you know, demonstrating that plasticity is all over the place, is ubiquitous, etc., but also advancing a fairly controversial idea, which then she elaborated in a major book that she published a few years later, arguing that sometimes, evolutionary change does not start with a genetic change, which has been the assumption ever since the discovery of Mendel, but starts with a plastic shift, with a change in environment that causes a change in phenotype, even though the genotype remains the same. And then the genes basically, genetic variation ensues later, and it's selected in order to stabilize this phenotype. So, the way this would work is like, I can give you an example that one of my students and I had worked on for some time. So, there are certain plants that are semi-aquatic, so they live in environments where the level of the water fluctuates during either the day or the seasons, depending on the situation. And these plants typically have developed two different kinds of leaves -- one underwater and another one above water. These leaves are anatomically different, they look different, they're physiologically different as well. So, it's a case of intra-individual plasticity, basically, because the environment is, you know, the individual is actually experiencing two different environments, and so below water does one thing, above water does another thing. It's the same genotype, obviously, because it's the same organism, right. Now, lots of people, and not just my student and I, but other people as well, have discovered that what happens is that if, for whatever reason, the environment permanently shifts one way or the other, so the lake or whatever it is becomes you know, the level of the water goes down permanently, so that now the environment is that these plants experience is only the [word I can’t distinguish] or vice versa, the water level goes up, and the plants essentially become completely aquatic. Then there is a shift in phenotype, obviously. The plant is already, it's basically pre-adapted to either one of these two environments, because it's already capable of living in those environments, except that instead of doing it temporarily, it does it permanently. Now, the plants that are capable of doing this shift, the plastic shift, will be able to survive a change in the environment, and then what happens over a period of time of course, so initially there is no genetic change, but over a period of time, new mutations will come into the population. Some of these mutations will be able to fix the new phenotype, to make it more stable, to make it less sensitive to environmental changes, because now it's now no longer necessary to actually have the plasticity, and then you have the sort of fixation of these new phenotypes by genetic means, by natural selection and genetics. So basically, what West- Eberhard was saying, has been saying, is look, sometimes what happens is the first step in evolution is not the appearance of a mutation, but rather an environmental change, and those members of the population that are pre-adapted, at least in part, even at a suboptimal level, to the new environment, shift to the new environment by means of plasticity, by an entirely phenotypic change. And then, that gives time to the population to survive, basically, instead of being eliminated immediately, it hangs around a little bit, and the longer it hangs around, the more likely it is that there will be beneficial mutations that are going to be selected and further fine-tuned and stabilized effects. So, this phenomenon is called genetic, phenotypic accommodation, and it is a result of the fact that the plant is plastic to begin with. So, the issue here now is if this is true, and we do have a number of cases where this is definitely true, the question is how frequently does that happen? But even if it's only occasional, the thing is, this is a major departure from standard evolutionary theory, because you have an evolutionary change that is not initiated by way of a mutation. Does that amount to a rejection of Darwinism and all of that? So no, it just means that guess what? There is one more mechanism by which, you know, living species can adapt to novel environments.
20:34
AW: Massimo, I want to ask you a sort of theoretical extension of one of the things that you were just talking about, but before we do that, I think it would help our listeners if we go back and talk about phenotypic plasticity in humans, and maybe just give some examples of, you know, what are the important kinds of phenotypic plasticity, you know, what's the difference between developmental plasticity and sort of short-term reversible changes? You know, if I go out and run around the building, my heart rate's going to go up, so the genotype...my phenotype has changed, so is that plasticity?
MP: That is plasticity, but it's the kind of plasticity that is, as you say, it's not really directly relevant. I mean it is relevant because you do survive better precisely because your heart rate adjusts, right, depending on circumstances. But it is reversible. Most of the studies have been done on developmental plasticity, not reversible plasticity. So, often the difference is drawn as developmental versus physiological plasticity. So, heart rate is an example of physiological plasticity. But your height, for instance, is an example of developmental plasticity. Now we know in human beings that the height is the result in part of genes and in part of the environment. You know, we know that people with better diet on average become taller, and you know, other things [word I can’t distinguish]. We also know that there are mutations that affect human height. So, we do know that both of them are important. The problem with human beings in particular is that it's hard to actually trace the reaction arms, that is do those diagrams that I was referring to earlier, because that would require controlled experiments in which you breed people on purpose, large numbers of them, and then you wait 30 years until they grow up, you know, you put them in the different environment, controlled environments, and then you can imagine that this is not only logistically but also ethically not possible, just not possible.
AW: Suspect on many fronts.
22:29
MP: Yes. So, one of the problems, what that means is that really, we don't know what the shape of human reaction arms is. We have very good indirect evidence that environmental effects are relevant for certain human traits. We have also very good indirect evidence that genetic effects are important for certain human traits. We don't know how the two interact together, because the only way that I know of in order to figure out a reaction arm is to do the controlled experiment that I just mentioned, which is impossible in human beings. So that is what makes me very skeptical of anyone who claims to know anything about human reaction arms. So, and you know, there are two camps. There are the geneticists who say, "No no no, it's mostly genetics." What do you mean, mostly? How do you measure that? And then there's the other camp, usually in the social sciences, people that say, "No, genetics has nothing to do with things like human intelligence or behavioral traits, or things." Like how do you know that? How did you measure that also? It's just like really bizarre that people make these really confident statements about either the inheritability or the environmental effects on human traits, especially on human, complex human behavioral traits. They don't know. Again, I'm going to use [name I can't distinguish]. He came up with this wonderful analogy a number of years ago to explain what the problem is with gene-environment interactions. So, he said, look. Imagine you're building a house, and instead of in the United States where most houses are built of wood, which is why they don't last, you build it, you know, the old-fashioned way, the European way, with bricks and lime, okay. So, you say, okay. So, you start putting the first layer of bricks and then lime on it, and then bricks and lime and bricks and lime. Now, once you get the final house, you could if you wanted, ask the very quantitative question, "Well, what is the weight of the house in bricks, and what is the weight of the house in lime?" And there is an answer to that question, and I'm sure it would be something like, you know, 98% bricks and 2% lime. That tells you precisely nothing about how to build a house, because it isn't, you know, you're not going to come up with 98 bricks and then 2 little pieces of lime and then you say, "Oh I got the house." No. You get the house by the specific patterning of the bricks and the lime, right? And so the idea there is that even if you could show that, let's say 90% of genetic variation in phenotypes in a particular human trait, is the result of genetic influences, that still doesn't mean that the way in which it is usually interpreted, "Oh so genes do all of the work and the environment is not important." You take out that 10% in that specific pattern and you get nothing. Absolutely nothing. Because genes by themselves don't do crap. So, it's really bizarre how people still today, after decades and decades and decades of phenotypic plasticity, gene-environment interactions, etc., they still come up with very simplistic things like "Oh, its 80% genetics." No, it's not.
25:36
MM: So, shall we switch gears and maybe spend some time on niche construction, another completely accepted, very well understood, not complicated at all concept.
AW: I'll start by saying, one of your big five ideas is about niche construction, so why do you think that's an important player in this extended evolutionary synthesis?
MP: Broadly speaking, the relevant environmental factors that an organism uses, or resources I should say, environmental resources that an organism uses in order to live, okay, to thrive. Now, early on ecologists thought that there could be such a thing as an empty niche. An empty niche would be a set of environmental resources that are basically waiting for an organism to discover them and to, you know, get there. That concept is no longer, doesn't have a lot of purchase in modern ecological theory because ecologists have come to agree that niches are constructed, meaning that it's a dialectical relationship between the organism and the environment. The organism develops certain ways of life, in part because it lives in a certain environment, but in doing so, it alters that environment to suit its own needs, and so it's a continuous positive feedback between environment and organism, so that the idea that a niche is just out there waiting to be filled has been discarded at this point. I mean there is still a sense in which one can think of some major conditions in evolutionary time as a discovery of new niches, like for instance when, up to a point in the history of life on Earth, there were no terrestrial animals, right, or for that matter the rest were plants. But once that something has made that first step, with only in the case of animals, then all sorts of possibilities got opened up to exploring and lots of resources that were not available there, not available earlier. So, in that...
AW: But presumably, I mean, that transition to land also resulted in the transformation of the land itself, so they're constructing the niche for themselves and for other species that are following, right?
27:56
MP: Exactly. So, you can say that yeah, initially there were some opportunities that were not exploited or potential opportunities, but as soon as something started exploiting in them, then there is this process of interaction with the environment and sort of reciprocal modification. So, niche construction in general now is referred to as this continuous feedback between the organism and the environment. Now, the classic examples of obvious niche construction are things like beavers' dams, things like that, right? So where an organism goes out there and actively modifies its own environment in a way that then has consequences not only for its own lifestyle, but actually on the lifestyle of a bunch of other things, because once the dam is being built in a river, then all sorts of stuff gets affected, not just the beaver, right? Not only that, but niche construction in the modern sense of the term, in the sense that people tend to use within the extended evolutionary synthesis, refers to a process of inheritance in some sense, meaning that organisms don't inherit just their genes (obviously they do), but they inherit important components of their environment. So, it's particularly the one they have constructed. And so, they don't start from scratch every generation. You know, an organism leaves to its offspring a certain environment that that organism has modified, you know, sort of why that is likely to make that progeny more capable, you know, of surviving, reproducing, etcetera, etcetera, right? So the idea therefore of modern supporters of niche construction like Kevin Laland (?) and Kim Sterelny (?) and John Odling-Smee, and people like that, is that evolutionary theory should be expanded to include the concept of environmental inheritance, of the fact that, you know, organisms don't start from scratch, just like genes. It's, if you think about it, I mean at least from my perspective, it's whether it should be, it is, but it should be a rather uncontroversial concept, because just in the same way in which development biologists have discovered that you don't inherit just your genes from your parents, you inherit a lot of cytoplasm in the first, you know, in the fertilized zygote. Without that cytoplasm, the genes don't do crap again. Because by themselves they don't do anything, right? So you need that cytoplasm because nutrients, you need enzymes, you need, you know you need proteins, you need stuff that actually makes the metabolism work, and reproduces, you know that opens up the DNA, replicates it, etc. etc. etc. Without that, you don't get an organism. Nothing gets started. You just have a bunch of DNA that stays there and does nothing, right? So in the same way in which we have what is called extra-genetic inheritance, that whole stuff is referred to as extra-genetic inheritance, you also inherit your, you know, certain number of sub-cellular organelles, like mitochondria, which of course they have their own DNA, but you inherit not just their DNA, you don't build, nobody builds mitochondria from scratch. You inherit the mitochondria. You need a certain number of mitochondria. If you're a plant, you also inherit chloroplasts, you don't start that from scratch either, right? So, and if, in fact, if you did try to start everything from scratch, again you would not have a viable organism. So just in the same way in which there is genetic inheritance and there is extra-genetic developmental inheritance, the idea is simply to expand it even further, not just to the internal environment of an organism, but to the external environment. Bodies themselves don't start from scratch in the external environment. They are born into an environment that is, the fancy term is autocorrelated with the environment of previous generations, right? Your environment is similar to the one that was experienced by your grandparents and your parents and things like that. And that is a good thing, because if it were not correlated with the environment experienced by your ancestors, immediate ancestors, then you would probably not be adapted to that environment. You'd find yourself in sort of, you know, a bad situation because now your genetic and developmental machinery are tailored for a particular environment, you'd find yourself in a completely different environment. It's like, ah now what? You're likely, more likely than not you're going to die. So that's what I mean, niche construction, so niche construction is different from niche, from the inheritance, from environmental inheritance. But, and that's actually a major difference between again, the modern synthesis and the extended synthesis. The modern synthesis does accept the concept of niche construction. It's definitely there. It's been documented by ecologists for decades, so it's not controversial. What is controversial is whether we should consider the inheritance of information and material from the environment as a separate channel of inheritance along the side of genetic inheritance and extra-genetic inheritance or not, what difference does that make.
32:56
AW: So, if I look back, you know, at the literature over the last 10 or 15 years, there's been quite a bit of pushback against this idea. So, why do you think it continues to be controversial?
MP: Gene centrism. I mean, it's, I have no other answer other than some people are just fixated with the dang genes! You know, and...
AW: Which we've already established don't do crap by themselves!
MP: And that's right!
MM: That must be the title of the podcast, by the way.
MP: I like that, "Genes don't do crap!" No, I mean I don't understand, I mean I honestly have a hard time understanding this thing, because all this stuff is well known. It's not, nobody really says, "Oh no, there is no such thing as extra-genetic inheritance," or there is no such thing as niche construction. It's all a question of oh but it's less important. Well, now we go back to the bricks and the lime. What do you mean it's less important? Numerically maybe, although I would like to see how you actually measure that, because you could put it in terms of mass, certain the genes are not very important, because they don't have a lot of mass. So, now, people talk in terms of information, right, and they say, well genes have, carry information and the rest of the stuff does not. But of course, it does! There is information in the environment, there is information in the developmental systems of organisms, you don't, and the demonstration that that information not only is there, but that it's crucial, is again, that if you take it out, you don't get a viable organism. You just don't. The genes by themselves are not capable of reproducing all of that information. In fact, one of the things that really bothers me is that all these objections about extra-genetic inheritance and developmental inheritance -- they all make it much more difficult for biologists to explain how natural selection could possibly do things. Because if you take all of this other stuff out, right, then it's up to the genes to do the whole work, the whole thing. And the genes, we know, simply do not have, cannot have stored that amount of information. Let me give an example. Just think about the number of interconnections in your brain. There are billions of neurons in your brain, and they're all interconnected to a bunch of other neurons. So that means billions and billions and millions of connections. If your genes had to specify the exact location of those interconnections in your, in the adult human brain, your genome would have to be orders of magnitude larger than it is. This is a simple calculation -- you can figure it out, okay? It's not, we know this for a fact. So how does that work? Well it works because throughout development, neurons make their interconnections by mechanisms that don't, are not directly the result of genetic information. They just sense each other, you know, the proximity of other neurons. They arrange themselves in certain ways, and so the brain gets built, in part, certainly under genetic direction, because if there were, if you don't have the right proteins in the right place and the right moment, nothing happens.
AW: So, you might say that the genes are encoding the rules for how the neurons hook themselves up, at some level.
36:10
MP: Correct. That's right. That's right. The genes are encoding the general rule.
AW: So, I myself have worked on a number of niche-constructing organisms, mostly insects that make leaf rolls (?), or you know, tent caterpillars that construct these elaborate tents that modify sometimes in pretty profound ways the thermal environment that the caterpillars are experiencing. But I don't want to talk about those, I want to talk about humans as niche constructors, and just get your ideas about how important is niche construction in our own ecology and evolution and culture? I mean obviously I'm here inside of a, you know, an air-conditioned niche in Montana, and I'm perfectly warm over the winter and reasonably cool over the summer. I'm not experiencing that outdoor, and I'm, you know, in the sense I've transformed my niche, but it's not something that my genome built, it's not something that, you know. So, there's some complicated issues there, and I'd like to know what you think about that.
37:08
MP: I'm sorry, I think, so there is a lot of research that has been done currently, as we speak, on that aspect, so applying the concept of niche construction to cultural evolution in humans. And you could argue that the whole of the reason evolution in humans, meaning the last, at least, 20,000 years, but probably more, has been a question of niche construction, right? That, and we, the interesting thing in that respect is that although people have tried, and they're trying, we don't really have a good theory of cultural evolution. You know, people talk about cultural evolution in sort of metaphorical terms, like, oh yeah, culture has evolved, meaning that they change over time. And there's been occasionally an, a sort of attempt to put together a more fundamental theory like the brief period where people were talking about memes as analogous, as directly analogous to genes, but as far as I can tell, memetics has gone nowhere except as a metaphor, right. So, there are people who are trying to figure out exactly how does cultural evolution work, and how in fact, cultural evolution is superimposed to and interacting with biological evolution, because a lot of people, so let me open a small parenthesis. Lots of people think that, oh because we have culture, then human beings have stopped evolving biologically. Not at all! Not even a chance. It's, you know, we can measure, actually, natural selection in human beings in a bunch of different traits, the most obvious one, this has been known for decades, is that there is very strong stabilizing selection for weight at birth, right? So, meaning that natural selection acts so that the weight of babies at birth is within a certain range. If they are too large, they're going to kill the mother, and probably therefore also kill themselves, and if they are too small, they are not going to be able to survive. Now, and you can measure that, you can actually quantify the intensity of stabilizing the skull, stabilizing selection because it tends to stabilize around the mean, right, as opposed to pushing one way or the other, which would be directional selection. Now, it's also true however, that of course, technological inventions have now relaxed that natural selection, right? So, if you had an incubator and you can get babies, viable babies out, you know, earlier on when they are smaller and put them in an incubator, now that relaxes, that counters natural selection for you know, stabilizing selection for weight of birth. But even that can be done only within certain limits. You can't just take, at the moment at the least, you can't just take a zygote and put it, and take it out of the mother and put it and grow it on its own -- we can't do that at the moment. So, so there is concept interaction between biological evolution and cultural evolution, right? But you can argue that we have changed much more culturally than biologically over the last, you know, 200,000 years. There is the, the fossil record tells us there is no difference in cranial capacity, which of course is only a rough measure of brain ability and all that, but still, in terms of cranial capacity and probably of brain anatomy, there has been no difference between the three of us now and some, a man in the place [word I can’t distinguish].
40:18
MM: This might be a little bit challenging, but I guess, we did want to try to wrap up with the potential interface between these two big ideas that we've talked about. Is it too late in the day to wrap one's head around the relationship between niche construction and plasticity?
MP: Sure, we can try that and then we'll leave the other ideas for another episode.
MM: For another try, yeah.
MP: So, in some sense they are directly connected because niche construction is made possible, in part at least, by the fact that there is behavioral plasticity in the organism, right, so again to go back to the classic example of the beavers' dams, beavers, you know, probably have a, certainly have an instinct on how to do that kind of stuff, but they also react to their environment, to their immediate environment, to the materials that they find around them, which might not be the same every time. They may not, and certainly they are not encoded genetically. So, they show behavioral plasticity. Human beings, obviously, have a huge amount of behavioral plasticity. I mean, we can, we adapt behaviorally to all sorts of things, situations. And behavioral plasticity is a type, is one particular type of plasticity, right, so it's different from developmental plasticity, but it is certainly an important type of plasticity. In fact, the argument has been made that if anything, if plasticity affects the rate of evolution of species, that is particularly the case when we are talking about species that are behaviorally plastic, and that's not just human beings, that's any large brained mammal, so including other primates for instance, especially social primates including the dolphins and other situations that I was talking about earlier, and possibly also including birds, for instance. So, there is lots of behavioral plasticity that is found in the animal world, especially among the smartest animals, the animals that react, you know, in a more flexible fashion to environmental challenges. And, so from there, the connection with niche construction becomes pretty obvious, because if you're behaviorally plastic, then you can invent new ways of altering your environment and of receiving information and using information about your environment from one generation to the next.
MM: Well, thank you so much for your time! I appreciate it, it was fantastic! Yeah, I definitely learned a lot, and uh, yeah! It was really good
AW: Pleasure talking to you!
MP: It was a pleasure. Thank you, guys.
MM: Okay, alright! We'll talk to you soon, thank you!
AW: A special thanks to Matt Blois for editing and production help. Thanks also to Gerard Sapes, Romain N=Boisseau, Devin O'Brien, Steve Lane, Victoria Dolloff, Haley Hanson, Holly Kellvitas [spelling?], Travis Flock, Meredith Kernbach [spelling?], Chloe Ramsey, Jeff Ohlberding, Lars Shanley, Cynthia Downs, and Suzanne [last name I can’t distinguish].