One feature common to nonlinear phenomena is how they challenge intuitions. Maybe nowhere is this more apparent than in studying the evolutionary process, and organisms in which not just genes but learned behaviors reproduce themselves provide a fountain of reliable surprises. Teasing out the intricate dynamics of gene-culture co-evolution is no easy feat. The dance of language, tools, and rituals together with anatomy reveals a deeper hidden order in how information spreads, and offers clues to why some strategies for innovation repeat themselves across the tree of life.
This week’s guest is Nicole Creanza, an Assistant Professor in the Biological Sciences department at Vanderbilt University whose research merges computational and theoretical approaches to the comparison of cultural and genetic evolution in both human languages and birdsong. In this episode, we discuss how geography, genetics, behavior, and technology collide in fascinating ways and how the study of gene-culture interactions might answer some of natural history’s greatest riddles.
Nicole’s Website.
Nicole’s Google Scholar Page.
Nicole’s Santa Fe Institute Seminar: Cultural Evolution in Structured Populations.
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Michael
Nicole Creanza, it's a pleasure to have you on Complexity Podcast.
Nicole
Thank you so much.
Michael
So I like to start these episodes by inviting guests to talk a little bit about their own intellectual biography, you know, how you came to a passion for science and the study of evolution and how you came to do the work that you're doing?
Nicole
Of course. So I think my passion for evolution probably started in ninth grade. And I read in biology class, kind of the first inklings that I had about about evolutionary theory and learning about Darwin, and learning about how animals evolved in plants evolved, and immediately wanted to take AP Bio as a sophomore and just dig in as much as I could. I felt like this was an idea that made everything makes sense for me.
And so I was an early devotee, and and that's kind of shaped I think how I think about the world around me and my interactions with it.
Michael
So a lot of your work emphasizes the cultural dimensions of evolution. And I think the right place to start is, in the broadest way, looking at the differences that we understand between molecular evolution and cultural evolution. What are those? What significant differences do we observe? Why does observing those differences matter to the study of social organisms in particular?
Nicole
That’s a super interesting question. I think that that's something that I have been interested in in for a really long time, thinking about the parallels and differences between genetic evolution and the evolution of behavior. And I started out, in my PhD I want I thought I wanted to study animal behavior. And that was one of the things I was looking for when I was looking for graduate school and so I ended up studying birds.
Someone has told me since that there are two types of people who watch birds in the wild. And obviously there's lots of types of people. But you can often categorize people into the ones who want to see as many different types of birds as possible and the ones who are content to kind of hide and watch a boring bird just eat and hide its food and interact with others and I definitely found myself in that second category, boring or not—and who's to call a bird boring?—but I really wanted to kind of figure out behavioral patterns and think about animals and humans and and how they behave the way they do, and how we think about about how ideas are transmitted in humans, and finding the parallels between that and how animals transmit their behaviors, and learn from one another. And so, I just kept building on these ideas becoming more and more fascinated by them.
Michael
What are some of the important distinctions to be made between say, Mandela and inheritance and what is popular, popularly understood as like memetic inheritance following, Richard Dawkins in The Selfish Gene?
Nicole
Sure. So, I think that, that the main difference and that that's easiest to point to is that, as humans and for birds as well, and for many if not most other organisms, we inherit our genes from our parents, and we call that vertical transmission, and we can inherit our behaviors or learn our behaviors from many other sources. And so we have not only our parents but other adults in the population: people our own age, teachers who are dedicated to transmitting information, for example, and we can also come up with their own ideas, we can innovate, we can change our own minds.
So the number of input sources that we have for behaviors and for culture is much higher in general and is not limited to kind of the time of our inception. That we also have our whole lives to acquire traits and behaviors and change them. And so there's the potential for so much more complexity, I think, in learned behaviors, as opposed to Mendelian inheritance, because we have so long, and so many sources from which we can acquire information.
Michael
There's a there's another dimension to this that you point out in a review that you lead authored for PNAS on “Cultural evolutionary theory: how culture evolves and why it matters.” You mentioned that it's possible that children are likely to reject cultural traits that they might inherit from their parents. I can't remember who authored this research, but I did see something about political dispositions oscillating over generations.
Nicole
Yeah, there’s a paper that's called something like “Haircuts, and hemlines” as well, about how things that you observe in your parents generation seeming particularly outdated or worthy of rejection, and that we certainly inherit lots of ideas from our parents. As much as you can point to examples of rejecting, for example, the political beliefs or religious beliefs of your parents. Those things do tend to correlate we do more often than not learn some of those types of traits, political beliefs, for example, from our parents. And so you can identify both patterns and that kind of very easily, anecdotally. You can see that culture evolution can be really complex. If you have some probability of adopting a belief and some probability of wholeheartedly rejecting it, you How do we look at evolutionary patterns, then?
Michael
And then, a lot of your work has emphasized the nonlinear ways in which cultural evolution changes patterns of genetic inheritance, also.
Nicole
That's right. Yeah, we think we think about a couple different ways that that could happen. You know, we all look for certain things in our partners, depending on what those what those things are, if they behaviors or beliefs or commitments to do certain things, then we narrow the field of people that we're willing to partner with, potentially by cultural factors. And so those can have evolutionary implications.
People have realized for a long time that we're that humans are geographically structured that we're much more likely than not to to partner with someone that we are nearby at, and that we're, you know, likely to be nearby to where, where we were born, kind of over the course of evolutionary history. And so in addition to these geographic patterns, we can also see linguistic patterns so you're more likely to partner with someone who's whose language you share. And there's other beliefs that people and behaviors that people we call this assortative mating. And so you can assort on many different types of traits, and then those traits can become correlated with genetic evolution.
Michael
Maybe it seems like the next step is to start with some of the things that you brought up in the talk that you gave it to Santa Fe Institute this week, on your work in in modeling the contact between populations, and using the diversity of tools and techniques available to different populations, and understanding how the the cultural repertoire is affected by migration between populations and by different kinds of food gathering or production. I guess maybe the right place to start with this is this paper that you wrote for the Royal Society Interface, “Greater than the sum of its parts” that was co-authored with Oren Kolodny and SFI External Professor Marcus Feldman. And it starts with a puzzle, which is this transition between the middle and the Upper Paleolithic and this what archaeologists have had, or I guess, palaeoanthropologists?
Nicole
Yeah, both, I think.
Michael
…have had a hard time understanding about what they're seeing here. So let's start with that mystery.
Nicole
Are we and you're thinking 50,000 years ago, this one?
Michael
Yes
Nicole
So the there's lots of mysteries in the archaeological record. This does happen happen multiple times in human history: you can point to certain points in human history where there seems to have been a sea change where in a relatively narrow timespan, things in the in the cultural tool record in particular seem to shift. And there's lots of hypotheses about these about these types of transitions. And, and one is, similar to one that Darwin had about the fossil record, which is that if you have a very sparse and imperfect record, you can see patterns that that might not be there. So you can, if you if you only have a dinosaur fossil from every million years, you might think that there was rapid change when there was actually a very slow change.
And so that's certainly one thing that we need to think about with the archaeological record of human tools is that we we might have biased samples or incomplete records that could lead us to see patterns that that maybe aren't there. But if we think to ourselves that the record is representative of human behaviors, it does seem like there are certain periods of time when things when things have changed in relatively rapidly compared to the time period before.
Around 50,000 years ago, some scholars point to the emergence of art and jewelry and musical instruments and a couple things that in addition to an explosion of different types of tools, and have sought to explain this relatively rapid increase in in what seems like human cultural changes. And something that that I talked about the other day in the talk is that often, researchers had pin these changes on other things that were going on. So either there was a dramatic environmental shift, there was a change in the human brain…people have linked this to the emergence of language that if we could transmit information in a different way, linguistically, that maybe all these different types of behaviors could accumulate rapidly.
And something that we wanted to think about with and push against just just in terms of thinking in the vein of Occam's Razor, is this the simplest explanation that we can think of, that an environmental change or human cognitive change caused this big shift. And so, our hypothesis in in making this model and is that human culture itself could change the parameters of its own evolution. And so if we think about populations coming into contact with one another that have different sets of traits, different sets of tools, if they can combine those tools and and make plenty of new things that may be kind of an increase in your human population size or in in human movements could have led to an explosion of tools without having to invoke a cognitive genetic or environmental process. We can come up with other hypotheses, but the idea was, can we think of just a purely cultural process that would lead to some of those patterns? Or do we need to invoke something external? And so the the point of the model was mostly to kind of give this give this other null hypothesis.
Michael
So there's a couple of really interesting features of this model. One one is that you account for the way that these interactions might change the rate at which certain cultural innovations are forgotten. Many people, including Brian Arthur, have put forward models of the evolution of technology in which nothing is really lost, but that seems to be biased toward recent history. And so I'd love to hear you talk about that and your model shows about the way that technological advancements are stabilized by this kind of mixing.
Nicole
Yeah, so there's um there's a couple different things that we propose. As a background, there have been anthropological and archaeological studies of cultures that seemed to point to the fact that tools can be lost even when they're useful. So we it's unknown, the processes. We’ve had a lot of hypotheses because we can't go back in time and ask people why did you stop fishing or why aren't you making this tool anymore?
So some of these hypotheses have to do with the rate of spontaneous loss and particularly how it relates to population size. So there's a very influential model from 2004 by Joe Heinrich, that postulates that population size is related to the rate of loss of cultural tools. Say that you're trying to make a needle to sew clothes, and there's a person in the population that you've identified as the best person at making needles, you would seek out that person and attempt to learn their techniques. And that on average, you're likely to do maybe a little bit worse than the best person. So you've picked a model, you've tried to imitate it, and you've come pretty close, maybe, but not to the level of proficiency of the master.
But if, say, 1000 people tried to learn that technique, a couple of them might make an even better needle, they might kind of figure out a technique that was a little bit better. And so if you had a large population, every generation, your best model might get a little bit better. And then over the course of time, the average proficiency of that trait might shift upwards. Whereas if you have a very small population, just due to the sampling of that space of proficiency, maybe your average best model would decrease in proficiency over time.
This was one mechanism by which population size could be related to the loss of tools. And so one of the things that we think about in in that paper is then if you have multiple groups of individuals, if this process is going on, or if other processes are going on, they might not have all lost the same set of tools. So if people are communicating with each other, if they're migrating, if they're contacting each other. Tools on average might be slower to be lost because they can be either reintroduced or a substitute for them could be introduced from another population. And so the isolation kind of also might lead to cultural losses that could be kind of reseeded if you have contact with our populations. And we also postulate in that paper and another one that things like writing systems or oral histories could preserve cultural traits as well…that if your best model of making that tool isn't as good as it used to be, but someone wrote down some information before, then you might have a better chance of preserving that that cultural process.
Michael
You’re talking about “lucky leaps”?
Nicole
Yeah, and the and that if you invent something like a writing system, that that people might or a drawing system or an oral history, that even if you get in a situation where only a few people were making some big innovation, only a few people were specialized in making a net or making an arrowhead or making you know something else, if people had written about it or drawn it, then maybe it's less likely to be to be lost or forgotten.
Michael
One thing that is really cool about this is that you're running multiple simulations, like you're talking about different populations of people.
Nicole
Yeah.
Michael
And then you're blending them at different rates. So there's there's infrequent or rare migration, and then frequent migration. And the rate at which cultural interchange is happening has pretty profound effects on not just the retention of innovations, but the accumulation of these sort of ratcheting innovations that maintain a memory or a history.
Nicole
Yeah, and that's one of the reasons that we called the paper “Greater than the sum of its parts.” If two populations are having very regular contact with one another, that they could potentially have a maintain a culture repertoire that was greater than either of them would have independently or that a population of both their sizes added together would have. That you can design a simulation in which people are continually combining each other's tools and looking to one another for for innovations and kind of maintaining a cultural repertoire, that's larger than either would be on its own. And so that's this is a theoretical thing. This is something that happens in the simulation. But the idea is that if you make a certain set of relatively simple assumptions about how cultural traits could mix when two groups of people come together. You can make some of these different predictions about how the cultural repertoire would change when the populations are contracting with one another versus when they're isolated from one another.
Michael
So, there's a nuance here that it feels important to make explicit, which is, like you said, infrequently associated populations might lose different technologies. And so it's more of an island thing where they're going to kind of drift off in different directions, but the more they're in contact with one another, the more their mutual understanding, their shared toolkit base overlaps, and so this seems related pretty importantly to conversations about globalization.
Nicole
Yeah.
Michael
…and the way that we are seeing, at one scale a loss of local bookstores, regional dialects, this kind of thing. But on the other hand, as a species collectively, we're innovating at this completely insane, seemingly unprecedented rate. And I am curious to hear you expand a bit on that and how you weigh what is in one sense, a loss of cultural complexity—or cultural uniqueness—with an overall global gain.
Nicole
Yeah, it's, this is a super fascinating topic. And I think that our models have tried to think about this a little bit or try to expand on this. But I think that there's also a lot of really interesting work that's coming out in both in laboratory experiments and in anthropological experiments.
A lot of it shows that something that people call partial connectivity is actually the best thing for increasing innovations and kind of finding optimal solutions to problems. And so this is a really interesting concept. Actually Max Derex and Rob Boyd, who's external faculty here, have thought about this a lot: that if everyone is on the same page, so if there's if the world is totally flat, and we all know what one another are doing, I know how you're solving problems, and you know how I'm solving problems, and that's true of everyone that you come in contact with…it might be easier to solve problems in the short term, because you can kind of access everyone else's innovations and think about how everyone else is solving problems, but in the long term, if everyone converges on one solution to a problem, then the population overall is a little bit worse off. If I come up with a solution and you come up with a different solution, than if we have a harder problem, we have our unique or unique solutions to try to put together and see if they're kind of complementary in a way that helps us solve a bigger, harder problem.
And so if groups of people or individuals make independent innovations, they can often be combined to make even even better tools or even better innovations later. Recently, I was asked to comment on a paper that I found really fascinating where anthropologists measured a real social network in several groups of hunter gatherers, and showed that if they were all exchanging information, a trait would spread innovation, they would solve the problem more slowly than if they were spreading the information according to their actual social networks which they measured by giving these hunter-gatherer individuals, things to wear on their bodies that told them how close they were to other individuals. And it would spread even faster if they were only associating with exchanging ideas with their kin.
And so the more that they restricted their social networks, the faster innovations were able to spread and solve problems. And that's something that we get at a little bit with our model as well in in that if two groups of individuals are fully connected, if they're part of one population, and effectively indistinguishable from one another, culturally, that they have some repertoire of traits. But if they evolved their traits independently and didn't talk to one another and then later came together, they would have many more unique solutions to try when they were trying to figure out a solution to a problem.
And so this, I think, is a really interesting thing to keep in mind when we're talking about globalization. I think that diverse groups are great and can solve problems really, really well. And increasing diversity in our perspectives is really important. And so thinking about kind of how groups of people that come from a different perspective when they when they come together, they have a lot of unique things that can try when they're trying to solve a problem together. I think that's something that kind of becomes increasingly interesting and important as globalization happens.
Michael
I want to take this opportunity to link what you just said to work the Albert Kao talked about when he was on the show a couple weeks ago. And the work that he's done on social decision making and how over correlation can can impact that and his paper on modular decision-making and how coarse-graining at the level of the society by taking local polls, and then feeding them up into a higher level, seems to perform better under certain environmental conditions.
Nicole
Yeah, it's interesting, I think people are converging on this idea from from multiple perspectives: that we don't want to all have the exact same toolkit when we're approaching a problem.
Michael
You talked about the Derex and Boyd paper in that piece Oana Carja and you wrote on “The evolutionary advantage of cultural memory in heterogeneous contact networks.” And specifically, you mentioned that if subsets of the population worked separately, and then compare their solutions, the partially connected network in the Derek and Boyd paper produced a diversity of perspectives that produced often produce better combined results then completely connected populations. That seems linked to other work that you've written on the value to kind of evangelize hear the value of interdisciplinary collaborations…
Nicole
Yeah, yeah.
Michael
…and why it is that we're at a moment in the history of the practice of science, where it's no longer adaptive for us to remain siloed and chauvinistic in this regard.
Nicole
Yeah. With with some of my colleagues, in particular Oren Kolodny and Marcus Feldman, we organized a workshop that we called “Bridging cultural gaps: interdisciplinary approaches to cultural evolution”. But one of the things that we we realized, and and other people have realized also, is that the study of how humans change over time or how behaviors change is something that you can approach from lots of different disciplinary backgrounds. I come from an evolutionary biology background, but from anthropology and archaeology, this is obviously very relevant, but I think even in fields that we potentially collaborate with less often—economists or psychologists or cognitive scientists, human behavioral ecologists—these ideas have similar underpinnings, but are often either, studied in different ways or called things, different terminologies.
And so I think, putting people together in a room and having them talk out, what do you mean by this? Are you published on this paper? Or have you studied this system? And are coming at it from a totally different approach? How is it relevant? How can we make our work, how to speak the same language that's been I think, a source of, you know, creativity for for me and for the field. So think about how people with different training and different kind of fundamental perceptions or ways of studying things, how we can all come together and try to learn more about, about behavior about humans about evolution.
Michael
So there's, this seems like a good time to segue into the the paper that you wrote with Laurel Fogarty and “The niche construction of cultural complexity: interactions between innovations, population size, and the environment.” You made a point in in your talk here, that you unpack in this paper about how there isn't a universal linear relationship between the size of a population and its complexity, and that this has to do with the way that we deal with food. So I'd love to hear you talk about how this paper answers the like this debate in the sciences, about the relationship between these things and how you came about it. Like how you went into like attacking that problem.
Nicole
of course. So yeah Laurel Fogarty and I have have been collaborating and and also friends for for a long time now. This idea is originally hers and then we got to write this paper together which was real a real joy. But the the idea that we had had been thinking about and circling around was that there there are different schools of thought, as you mentioned, when it comes to the relationship between cultural complexity and population size. If you make some assumptions about about cultural evolution, cultural processes, then you might expect larger populations would have more cultural complexity or more tools, a larger cultural repertoire, and smaller populations would not.
But in some sense the the proof is in the pudding when you survey a population and you have a set of populations in a certain area and you try to count how many tools they have in that population, which is obviously hard—you try to count how many people there are, which is also pretty hard—and then make a correlation plot. And so, very hardworking people have been thinking about this in many different cultures. And they often come to different conclusions. And this has been a source of of debate in the field.
One of the early and foundational papers in this realm was that Michelle Klein and Rob Boyd looked at fishing populations in in parts of Oceania and found a relationship that the larger populations had larger tool repertoires, more complex technologies. But people have gone to other other places and not found that relationship. One of the things that that came out of that was was a debate that you found this relationship, but I didn't. So it can't be universal, it can't be something that we talk about, or make as an assumption of human culture. And I think that's a fair point. But from studying niche construction, which we've Laurel Fogarty and I had both been had been thinking about to bolt together and separately, which is the process by which humans can alter their environment and thus alter their evolution, that maybe there was something related to the human interaction with the environment that might be related to this.
So when we put together all of the studies that we could find, that had tried to make an association between human population sizes and cultural complexity, we saw a pretty stark pattern, which is that when people had surveyed hunter gatherer populations or other food gathering populations, they mostly did not find a relationship between population size and cultural complexity. But if they surveyed food-producing societies, so either agricultural societies, modern societies, other ways of producing food, they found this correlation between population size and cultural complexity. And so then our hypothesis was that maybe if we're saying, well, some population show this and some don’t so it isn't a pattern…maybe something that could explain the pattern is that humans that alter their environments, use their cultural tools or their technologies to modify environments in a way that produces food—agriculture is a canonical example—that maybe there's a different relationship between population size and cultural complexity, then there'd be in a hunter-gatherer population. And one of the there's different hypotheses that we could think about. That would link those ideas, one of which is that maybe populations that modify their environment to produce food are buffered in some sense against environmental changes, whereas in a hunter-gatherer population, if there's a severe drought or or other environmental change, the tools that they had been using might no longer be useful in the environment. So if there's a big foliage change, or say they move to a new location, maybe their tool repertoire is no longer well-suited to their environment. And so they instead of maintaining those tools, they they come up with new ones.
And so their tool repertoire would then be associated with environmental fluctuations and less so with their population sizes. Whereas if you have a population that is sedentary, that is modifying the environment, that even if there's some environmental changes they would still use the same tool repertoire to do their farming. And they build on that, potentially. And so this is not necessarily the be-all-end-all of this debate, but it's one way of thinking about how we know humans are complex, they have complex relationships with the environment…does that weigh in at all on the relationships between culture and the people that have that culture?
Michael
So there’re a couple different dimensions to this model that seem really important dimensions to differentiate. One is the the harshness of the environment, and then one is its variability, the rate at which things are changing, and the effect that the interplay between those two variables have on the rate of innovation. And then the relationship between those things and population size. You mentioned that when the effect of the environment on survival, and the rate of innovation is strong, the effect of population size is more complex. It depends crucially on how fast the environment is changing.
I'm reminded of Jessica Flack’s work on collective computation. In her community lecture, and some of her recent writing, she's pointed to the way that if you think of human societies as processing a collective computation, that we are, at the level of the society, encoding these coarse-grained details about the environment—but that that process breaks down when the environment is changing too rapidly. I'd love to hear you talk about the thresholds at which these different strategies emerge. You touched on this just a moment ago, but please go into more detail about what makes the difference in terms of the strategies for, you know, the kind of sort of pastoral environment that we're used to thinking about in terms of human history and the insanity that we've been living through as a species for the last hundred and fifty years.
Nicole
Yeah, it's interesting, because there're different ways or different senses in which our environments can be harsh. And one of the main correlates of that, in the models that we've done, is how many problems are there for you to solve. In some sense, in modern society, we've buffered ourselves against a lot of environmental changes. You can exist in a place that’s indoors that's 72 degrees all the time and you always have access to food. But we do have this other aspect of harshness where we do have a lot of problems to solve, we have a lot of things that that we can improve upon in our lives. And we potentially have the resources to do that. And so this proxy for how harsh an environment is a really interesting kind of scale. Because if you're living outside, environmental harshness, or the number of problems that you have to solve that in your environment, might mean something very different than if you're in a more modern situation. And so, if we think about environmental change, those two groups are in very different circumstances. In a modern society, in this building and the apartments we live in and the houses, we can buffer ourselves against them. Mental change reasonably well up to the point where it impacts our food sources or impacts our communication with one another. But if you are hunting and gathering and living outside, large environmental fluctuations can have a big impact on how you live and how you feed yourself and whether or not you're migrating. And so I think that these these things we can we can think of them in numerous senses, and I think they're all relevant to humans.
Michael
It seems like whether or not we have constructed stable niches for ourselves at the level of, like, air conditioning, there’s a common misperception that we've somehow ended natural selection…when in fact, it seems like natural selection is just operating at a different time scale or a different level of organization than it once did. Different dimensions?
Nicole
That's right. I think we've altered our own evolution for sure. But but the ways that that will affect long term human populations is not totally clear. And I think for cultural evolution, we certainly haven't stopped kind of the natural selection or drift or any other evolutionary process on cultural evolution on culture. Our culture is still changing quite fast.
A recent topic that I've been thinking about with of my collaborators, Oren Kolodny, is something that we're thinking of in terms of is necessity or opportunity, the mother of invention. So there's this phrase, “Necessity is the mother of invention,” that we point to to think about, when would we make a new solution to a problem? Maybe it’s that if we need something that isn't there, we figure out a way to solve that problem. But you can think of this both in a traditional context of humans interacting with their environment and also in a modern context. If we are kind of operating at our capacity for things we can handle, maybe we don't really have the time to to solve that problem. And so, in some sense, maybe opportunity is the mother of invention; that if I have the leisure time, if I have this wonderful week at Santa Fe Institute, I could potentially have let my thoughts drift to problems that I wouldn't solve if I was completely overbooked every single day.
Michael
This is why Johann Sebastian Bach wrote over 1000 works of music and his wife did not, raising all those kids. That’s an instance where opportunity is the mother of invention.
Nicole
Yeah. And she probably made a lot of innovations in in child rearing! We can think about some of the modern luxuries we have, where if we don't have to deal with raising our own food or regulating the temperature around us or we can keep lights on later into the night. But there's probably some balance there, right? There's some interplay between needing to solve problems and having the time to actually do it. And so where where are humans right now on that spectrum, and how can we think about the kind of larger problems that cultural innovations might help us with, and how do we give ourselves the space to solve them?
Michael
So, to link this back to the paper on “The evolutionary advantage of cultural memory and heterogeneous contact networks,” you emphasize in that paper the way that network structure can support or suppress innovation and variance. I was left reading this paper that we're just discussing now, with this question about how the difference between hunter gatherer societies and agricultural societies seems like it's taken a new shape in the modern era. That it's not just about food production; it's about the production and supply chains of all different kinds of things, including commercial goods and knowledge. It seems like when we're talking about the the instability of the environment, that there's a complex interplay. We're not talking about foraging foods now; we're talking about countries that depend on other countries for manufacturing basic goods and services. Like, what happens if China stopped shipping things to the United States because of the coronavirus? When those networks break down, people have been warning about this for decades, about the danger of food deserts in our metropolitan areas. I’m curious what your thoughts are on how this research might translate to insights into the way that a global economy might be affected by the sudden introduction of new structure in the network. So, how we're actually relaying goods and services and information?
Nicole
Yeah, that's a tough one. I think a lot of the solution to that type of problem depends on how long that how long the disruption lasts. One thing our models might predict is that if there's a short-term disruption of cultural networks, we would bounce back relatively quickly, but if it was a long-term disruption, we might not be able to in quite the same way. And so part of that, I think, is just what you're saying: that we would have to solve some problems that we wouldn't have to solve before. If we couldn't go to the grocery store and buy food, we would have an urgent necessity that we would that we would need to figure out. Our solution to that would probably depend on on how long it lasted. And then whether in a disconnected social network, we would innovate our own solutions, and hopefully figure out the ways to ways to survive and persist, which humans are quite good at doing. But I think it would take a very short amount of time before you realize that some of the knowledge you thought you had at your fingertips isn't isn't there anymore, and that you're you're forced to solve problems that you could have the answer to if your network connections still existed. That's something that would put modern humans in a bit of a tough spot, I think.
Michael
To get kind of morbid about this, there's a silver lining in this, which was that after however long that period of disruption might be, we will have pioneered all of these unique solutions to these problems. And maybe that kind of global disruption might actually kick us off of the local optimum we're stuck on because of the homogeneity of the global economy as it is.
Nicole
Yeah, I think the models would predict that, and that would be my hope, as well. But I'll keep my fingers crossed for that for that outcome.
Michael
So I want to move to… You’ve done is about as much work on birds as you have on humans. And I think the the analogies that emerge from looking at these two strands of your work stereoscopically are really interesting. I would like to have you talk about your work with Laurel Fogarty and Marcus Feldman on cultural niche construction of song repertoire, size and learning strategies and songbirds. It seems like there are very similar insights to the way that different cultures come together and mix and learn from one another, and the repertoire of tools that they have available to them. And a set of similar evolutionary pressures on why certain songbirds species might have a larger or smaller song repertoires.
Nicole
Yeah, I this is something that I’ve felt very lucky to study and think about this. It's endlessly fascinating for me to think about why birds sound the way they do. And so my students and I have been approaching this from a number of different perspectives, kind of some of those are based on on that the work that I did with Laurel Fogarty and Marcus Feldman on this. And the general idea that we were thinking about is that when I started to study birds, I found really, really interesting with that different species of birds have very different songs. The songbirds, the ossine songbirds are a clade of birds that are that share a common ancestor. Somewhere in that lineage, they, they evolved the ability to learn to sing. Like you mentioned with a cultural ratchet, it doesn't appear that any lineages of this in this clade have lost the ability to learn to sing. So we have several thousand species of songbirds with a common ancestor tens of millions of years ago, and the cultural evolution of their song has been going on ever since. So we have millions of years of cultural evolution that we can study if we if we can figure out how to parse and analyze bird songs and think about their long term evolutionary history.
Something that popped out to me as as being really fascinating is that some birds can learn to sing when they're juveniles. They they learn a song from an adult, potentially in the population. And then when sexual maturity hits the ability to learn the window of song learning closes. They have a sensitive period, and after that they can't learn more or modify their song. So they have this finite time period where they can learn and modify their cultural repertoire and then that's it.
Several independent evolutionary events have led to lineages of birds that can modify their songs, sometimes throughout their lives. Mimics and mockingbirds, for example, learn to sing, and they can modify that song and mimic other birds in the environment for the rest of their lives. This is a very different learning strategy. And in humans, you know, we learn languages best before puberty. After puberty, we can learn languages, but it's kind of a textbook way of learning and much less like an absorbing-from-our-environment way of learning. And so we were thought to have a sensitive period for language learning, but then something like toolmaking, you might preferentially do later in life and we have the window of different types. Learning occurs at different lengths in humans.
So I saw this opportunity to think about those two different strategies, you have a strategy. It's not a strategy that you opt into or out of as a birdl. It's a strategy or you're born with. Your strategy is either to learn your song early in life and have that song for the rest of your life, or to be able to modify a song that you have for the rest of your life. You might think, if the birds can modify their songs for the rest of their life, why wouldn't all birds just retain that ability? Why would that ability ever get lost in evolutionary history? Because it seems adaptive. It seems like if you're not doing very well with your song and attracting a mate, it'd be great to sing a different song and try again. And if you're if you're a bird that sings a very simple song, and it's unsuccessful in attracting a mate or defending a territory, you would have a second chance and that that fitness benefit might be great. So the thought process in the field was that maybe the ability to learn throughout your life is costly in some way, and that would explain why it would get lost unless it's critical for the birds’ reproduction or fitness. What we thought about in that paper is that if there's sexual selection for large song repertoires, that might be enough to offset the cost of learning throughout your life. If there's some kind of cognitive or metabolic cost of continuing to learn, then paying that cost wouldn't be worth it if the female that you're trying to attract is listening for a short and species specific sequence…but if the female that you're trying to attract is listening for maximum complexity, then maybe it's worth paying that cost to have longer to learn, to have a more complex song.
Then after that paper, which is a computational theoretical paper, we looked at real birds and found a similar similar trend. We looked at bird species where people had found a correlation between song complexity or repertoire size and reproductive success. For some species, singing the most elaborate songs means the most mates or leaving the most offspring, and those tended to be the same species of birds that already had large repertoires. We thought in that paper in terms of predictions you might make with other sexual selection signals, like a peacock’s tail. There are some birds that have really long tails, and canonically, this is thought of as a sexual selection signal—that females looking for mates would look at the birds with the longest and most beautiful tails and say, “You know, they had to evade predators and find food their whole lives while maintaining this beautiful tail. They must be pretty good at stuff, they must be pretty successful.” And so we can think about that in the same way with songs. If we're thinking about which bird species would have sexual selection that rewarded very complex and elaborate repertoires, then at the species level, we would look for birds that had those elaborate songs. And then within those species, the individual variation correlates with fitness or reproductive success.
Michael
So I want to tie this to hypothetical work that I was just talking about with your husband before this conversation. Richard Doyle at Penn State, in his book Darwin's Pharmacy, puts together this argument that human language emerged out of a similar process of sexual selection for eloquence.
Nicole
That’s interesting, yeah.
Michael
It’s related to, as you cite in your work, Robert Lachlan and Peter Slater's work on the cultural trap. And I'm curious whether you think this is a fair analogy, or under what conditions you see the complexity of the songbird repertoire, and also the open ended and extensive period of learning, appearing? Because it seems like it remains unresolved in human evolution, but it is a compelling argument: that it was the complexity of human communities, and this growing burden on us to be able to describe more and more intricate phenomena that led to this ratchet in which we became more intelligent as we became more social. That our ability to communicate and express ourselves eloquently became more and more important. Do you think something similar is going on in songbirds? And if not, what factors are selecting for these larger repertoires? It seems to be different than just a long shiny pretty tail…
Nicole
Yeah, I think it's I think this is an interesting domain that we took to potentially compare humans and birds. I think we have to do so with obviously a large grain of salt. But the the something that that I some I haven't read the work you cite, which I would love to. It seems really relevant and interesting,
I think Dietrich Stout, and Kevin Laland has also done some work on this: how do we transmit something like a stone tool? In the archaeological record, we find pieces of stone that clearly had a purpose. They could they could scrape things and cut things. And so we we have an idea of their function based on their structure. But what wasn't really known was, what would it take for me to to share that knowledge with you? Could you look at this stone and then me and say, “Oh, that'd be good for cutting,” and make yourself one? Or would you need an apprenticeship?
What Kevin Laland's group found, was that these types of tools were dramatically easier to transmit with language than without. That just showing somebody and miming something, even if you knew how to do it, it was much more difficult to pick up the nuance than if you could explain in words what you were doing and why. And Dietrich Stout’s group found that it took many, many hours, a hundred hours of training and practice, to produce one of these stone tools. And these are things that are pretty early in the in human cultural repertoire. And so, with the caveat that now that we're good at explaining things in words, maybe we lean on that a lot…it does seem that human communication and human culture co-evolved and potentially facilitated each other's evolution.
That's something that we can we can think about it with birds because I think the bird songs are often anecdotally compared to both human language and human music. They’re both a learned vocalization, so the parallels between both speaking and singing are kind of readily apparent. But recently I've been working with my postdoc Emily Hudson on this idea that maybe a bird song is actually more like an arrowhead than it is a like a language. What if the purpose or the function of song is more like a tool than it is like a communication behavior? So, thinking about the way that that these that songs develop and and whether they are measured by their complexity or by their performance metrics—“How fast I can sing, how stereotyped can I sing, or how complex I can sing?” At least now that isn't exactly how we're measuring our linguistic capabilities: we’re trying to convey information.
So yeah, I think there're lots of parallels between bird songs and human culture and the way that they're learned and the way that they evolve. I think there're a lot of parallels. But it's been interesting to try to really tease apart. Thinking about a human cultural analog of bird songs, we can make a case for a number of different types of tools, or a number of different types of human behaviors. And which one of those is really the most relevant in which circumstance? It might be different if we're thinking about a bird that has a complex song versus a bird has very simple song that it needs to sing as fast as possible or as regularly as possible.
Michael
So that's where this other angle to this comes in, it seems with respect to what I remember from reading the Lachlan and Slater work on the cultural trap like fifteen years ago, was that the heterogeneity of the environment in which these birds live plays a big part in how far a bird that maybe only nests in one tree has to go to find another tree of the same species. There's something about having to learn a wider range of dialects, or something that ties loosely into these concerns that we've been talking about—about the amount of variability in the environment and how that affects us. There's this link between when I think about, in humans, the amount of education required as our as our society has gotten more complex. We're spending more years in school. We’re traveling further away and living in different cities that our parents. We’re having to learn entirely different customs. And so it seems like what qualifies as an adult is now twice the age that was, you know, say two hundred years ago. I'm curious what your thoughts are on geographic range and environmental heterogeneity and these kinds of concerns, and how that's figured into your thinking.
Nicole
Yeah, it’s interesting. I think that for both humans and birds, there’re things that we can think about in terms of geographic range, as you mentioned, and also kind of environmental flexibility, like the number of environments you've been exposed to or whether you're a specialist in your environment or a generalist. This is something that people have thought about for a long time with birds that have dialects. So there're lots of species of birds where the birds in one particular region, sing something very similar to one another. And you can go a couple miles over and the birds sound very different. They've structured themselves by these dialects. So Peter Marler, I think I've heard that he used to say that you could drop in blindfolded in the Bay Area of California and he would know where he was based on the white crowned sparrow dialect he had mapped these out. He was very in tune to them. They were really geographically structured and geographically informative. So then the idea that kind of naturally grew out of that observation of of song dialects was that the birds that sing a certain dialect were well adapted to that environment. That they’d grown up there.
Human dialects are potentially a little bit like this: you can recognize who grew up near you. And then you know, you have a set of common experiences, you're adapted to the same environment. And what that would predict genetically is that you might choose a mate that shares your dialect because you know that your mate would be well adapted to the same environment, and so would your offspring. And so the idea with song dialects was that they would potentially then correspond to genetic groupings, that you'd be more closely related to individuals with your own dialect than other dialects.
People started to study this and sample sparrows in particular from from different dialects and compare their genetic variation. And it's actually somewhat analogous to the human cultural complexity literature where some people found it and some people didn't depending on the bird, in the species that they were studying, and sometimes even the subspecies. Like within the white crowned sparrows, there were links between dialects and genetic clusters in some groups and not others, and so then we're left with this kind of burning question of, when is being adapted to your environment something that would be beneficial for you to look for in a mate, versus someone who has a different set of experiences and is potentially more flexible?
I think birds and humans are both worth maybe thinking about the same things when we when we think about, the individuals that we associate with and the individuals that we come in contact with and learn from. If they have our same environment, then we know that their information might be useful to us in our current context. But if we have someone that we're learning from from a different environment, then maybe what that does is kind of buffers us so that our information is useful in more contexts. For both bird songs and human behaviors and cultural repertoire, I think there's there's some kind of trade off there. And we we probably are all best suited doing some some mix of in our learning, seeking out information that's relevant in our current context and information that will be relevant if we if we spread our wings a little.
Michael
Nice. Yeah, that that seems related to one of the strains that that is constantly plucked around here, including work by Scott E. Page on diversity and work teams, and how the larger our context functionally that we inhabit, as social creatures, the more it seems to select for the ability to retain a kind of a cultural memory, like hedging your bets. I don’t know, I feel like we've covered a lot of ground!
Nicole
Yeah, me too. I think you could sum up by saying probably both humans and birds hedge their bets as much as they can. And that the more you can learn and the more flexible your learning is, the better you might be at hedging your bets. That's probably an adaptive strategy.
Michael
So for you what remains one of the greatest unsolved questions in this domain? What's going to be keeping you up at night for the next few years?
Nicole
I think there's a lot but in the bird space, this idea of cultural evolution on the multi-million year timescale is is certainly keeping me up at night. Something that my lab is doing, and where my students are bravely forging new ground, is looking at bird songs that have been recorded around the world and deposited into citizen science databases and trying to extract information from those and say, “Okay, we have hundreds of thousands of songs that people have wonderfully recorded and submitted online databases.” There seems like there's so much to learn about evolution from that resource, so we've been building computational tools and graphical user interfaces to extract information from the birdsong and then we are trying to map that information back onto phylogenies. And then to think about the evolutionary history of the bird. If we look at kind of the evolutionary history of bird species, and at their songs, what can we learn about how behavior evolves over time and about the evolutionary constraints on how that might affect how a bird sings?
In addition to all the problems a bird has to solve, if their voices might sound different if they are huge versus very tiny, if they learn for a long time versus not very long, if they're in dense foliage versus in the prairie, and so on. Then layered on top of that are the cultural pressures, sexual selection preferences, and the both male-male and male-female interactions that they're having. So thinking about all of the different evolutionary pressures on this learned behavior over time and space, what can we learn about how behaviors evolved over millions of years? It's a big question, but it's the one that's been really keeping me up at night for a long time.
Michael
Certainly a more difficult question (or maybe not) than why birds seem to be subject to some of the same evolutionary ratchets, but have not yet achieved, or may not be able to achieve, cumulative culture.
Nicole
Yeah. Why humans are so good at cumulative culture and other species are not—or maybe they're better at hiding it from us!—is a really interesting question. Thinking about social networks, cultural migrations, moving people moving from place to place, and the analogies that we can draw from that, and from our modeling and experiments on that. How can we think about them other animal behaviors is something that we're still working on.
Michael
So it’s not just the thumbs! Well, Nicole, thank you so much for your time. I really enjoyed the talk, which I will link to in the show notes. It's up on the SFI YouTube, and we'll link to all the research papers that we discussed here.
Nicole
Thank you so much. This has been a blast.
Michael
Where would you send people who are, for whatever reason, unable to access the show notes?
Nicole
I have a website, NicoleCreanza.com, and CreanzaLab.com is a website that my students put together. It's been really, really fun. And Google Scholar. And then I think your website. Anywhere you want to reach me, feel free. Awesome! Thanks again. Thank you so much.