The Imitation Factor: Evolution Beyond The Gene - Hardcover

Dugatkin, Lee Alan

Hardcover

ISBN 10: 0684864533 ISBN 13: 9780684864532

Publisher: Free Press, 2001

Synopsis

A biologist and science journalist focuses on imitation as a key evolutionary strategy, revealing "animal education" as a universal phenomena.

About this title

About the Author

Lee Alan Dugatkin writes a monthly science column for the Louisville Courier-Journal, and has written for Scientific American, BioScience, and many other popular and academic journals. He is an Associate Professor of Biology at the University of Louisville.

Reviews

The dominant paradigm in evolutionary biology asserts that genes are responsible for virtually all manifestations of animal behavior while the environment plays a small role. In a thoroughly engaging, accessible manner, Dugatkin, professor of biology at the University of Louisville, challenges "that assumption by presenting the case that cultural transmission and gene-culture interactions are serious, underestimated forces in evolutionary biology." He analyzes a broad array of behavioral studies conducted by himself, his students and many other scientists to demonstrate that animals imitate each other regularly, learn new behaviors from this mimesis and even engage in activities that are best called teaching. By presenting behavioral examples of simple and complex animals ranging from guppies to macaques, from blackbirds to humans, he proves that large brains are not a prerequisite for imitation. Even more important, Dugatkin establishes these actions as constituents of culture, which many scientists limit to humans. Dugatkin explains scientific method superbly and conveys the thrill of designing an ingenious experiment. His theories and supporting evidence will inspire even the most skeptical readers to rethink humans' place in the animal kingdom. Anyone interested in the nature/culture debate will learn something new from Dugatkin. (Jan.)
Copyright 2000 Reed Business Information, Inc.

Dugatkin, biologist and science writer, spares the reader what he calls "the nasty mathematics" backing up his findings but provides a fascinating look at how the act of imitating affects evolution and culture. He offers interesting examples to prove theories on sexual and mating habits of barn swallows, scorpion flies, stalk-eyed flies, guppies, and humans as they imitate the behavior of others of their species and, thereby, transmit physical and cultural traits. Dugatkin reviews scientific findings from various disciplines and brings them together in a coherent picture of how humans and animals use the fundamental act of imitating to learn and adapt. Despite the human tendency to flatter ourselves that we're superior to animals, Dugatkin demonstrates how our behavior is quite similar to animals in the act of imitation and its value in transmitting culture and survival skills. Over millions of years, animals and humans have habitually imitated the behavior of those most successful at mating or hunting (or otherwise providing) thus preserving their species and guaranteeing survival. This is a very accessible, even entertaining, look at human and animal behavior and evolution. Vanessa Bush
Copyright © American Library Association. All rights reserved

Excerpt. © Reprinted by permission. All rights reserved.

Chapter One: The Cultured Animal

Imitation is natural to man from childhood, one of his advantages over the lower animals being this, that he is the most imitative creature in the world and learns at first by imitation.

ARISTOTLE

Aristotle raised all the best questions scientists are raising in laboratories today. That might be an overstatement, but if it is, it isn't a grand overstatement; it holds true for the basic questions that we address in my lab, as well as in the labs of many of my colleagues. But Aristotle was wrong, at least for the most part, about the ability of nonhuman animals to imitate. It was a big oversight. Nearly two and a half thousand years later, we discovered nature's blueprints -- genes -- but still remained almost blind to nature's way of transmitting information across the generations outside the genome. We tend to think we are the only animals able to do the trick of passing down the wisdom of our forebears. That trick is known as culture. Surprisingly, even guppies can do it.

Looking at infants and children, you can see that Aristotle is correct that humans learn first by imitation. A vast amount of preschool education comes from mimicking the behavior of others, usually parents. This is so obvious it can be scary. Looking at your child gives something of a mirror image of your own actions -- and that isn't always a pleasant experience. No one doubts the importance of imitation in humans. But Aristotle did not really recognize imitation as the root of cultural transmission, nor did he see that many animals, not only ourselves, have been able to transmit culture in just this way. Indeed, no one at all has recognized this until very recently. But it is now a scientific fact that illuminates the mysterious origin of culture itself -- and how evolution proceeds beyond the gene.

GUPPY CULTURE

I spend a lot of time watching guppies. To be honest, I spend more time with guppies than any sane person should, unless that person happens to be a behavioral ecologist -- someone who studies the evolution of social behavior -- and even then it is a close call. Watch guppies long enough, and you see that sex is what life in a guppy neighborhood (be it a tank or stream) revolves around. Males want to mate with any willing female, and spend a great deal of their time pursuing this desire. Females, on the other hand, spend the majority of their time avoiding the constant sexual harassment to which they are subjected. What determines who mates with whom in guppy society is a fascinating concoction of genetic drives and imitation. Females have a genetic predisposition to mate with colorful males, but layered on top of this is a strong inclination to imitate the choice of mates that other females make.

All else being equal, female guppies mate with colorful males and in essence obey their genetic code. But, hold everything constant, and females also imitate each other's choice of mating partner -- and that alone is a rather remarkable finding. Female guppies, with brains no bigger than a pinhead, copy each other's choice of mates. Yet the story of copying and mate choice hardly ends there. One can move on to ask how genes and culture interact to shape guppy mate choice. That is, if we consider copying and imitation (and teaching) to be forces underlying the cultural transmission of behavior, how do these forces interact with genes coding for behavior?

We might think guppies alone should not prove the likes of Aristotle wrong. However, the role of culture in animal life has been observed in many many species, and its effects are clearly quite powerful. Various forms of culture influence mate choice in everything from bugs, fish, and birds to deer and primates, including, of course, humans. In many of these instances, culture and genetics interact in unexpected and bizarre ways. Furthermore, culture is in no way restricted to the subject of mate choice; it invades virtually every aspect of animal behavior. Culture, or more specifically cultural transmission of information through imitation, was a force long before humans came on the scene and continues to be an important factor in what many would consider to be very simple animals. And imitation is a unique factor because the actions of a few individuals, if copied, can have long-term evolutionary consequences at the population level. The quirky behavior of just a few individuals can live on across the generations and across thousands, potentially even millions, of years.

That culture plays such a strong role in animal choice is a controversial claim and an even more consequential fact. Consider that cultural transmission of information can work with lightning speed (when compared with the timescale on which genetic change takes place). The action of even a single individual, if it is copied by many, can snowball through a population with evolutionary reverberation. Moreover, new theory in biology can predict when cultural or genetic factors will predominantly drive behavior. That we can now balance hereditary forces against cultural ones is an astonishing achievement of modern science. But we need to step back and define what culture really is and answer some related questions before we consider the larger implications of this work.

Evolutionary biologists are generally in agreement that the process of natural selection is the primary (but not exclusive) agent driving evolutionary change. There are certainly some prominent critics of this view, but most biologists would not quibble with this statement, especially if one were talking about the evolution of social behavior. To understand virtually any aspect of life on earth or elsewhere, scientists will tell you, we must understand how the process of natural selection operates.

NATURAL SELECTION AND GENES

Given the monumental impact of his work in both the social and natural sciences, it is often surprising to learn that Charles Robert Darwin's ideas with respect to natural selection are remarkably straightforward. Consider any characteristic of an organism -- height, weight, visual acuity, or anything else. If variations in this characteristic exist, such that, for example, there are differences in height among individuals in a population, and if there exists a means by which individuals of different height produce offspring that resemble themselves, then any variant that outreproduces others will spread through time.

If taller individuals, for whatever reason, have more offspring, over time we expect to see the average height of individuals in that population increase. If individuals who are slightly shorter produce more offspring, natural selection will, over time, methodically work toward producing a population of shorter individuals. This argument holds true even if there is a very slight edge in terms of the number of offspring that are raised. Through evolutionary time, small differences can accumulate into large changes. For example, if slightly taller individuals produce an average of 2.01 offspring per generation, with average individuals producing 2.00, then over time, natural selection will favor slightly taller individuals, and the population we are examining will be, on average, a bit taller than it used to be. It might take a while, but it will happen.

Darwin's theory was generic; it applied to any trait that met a few conditions he outlined in The Origin of Species. Behavioral biologists have long argued, as did Darwin himself, that the theory of natural selection is applicable not only to how an organism looks (anatomy, morphology, physiology), but to how it behaves as well. If a number of different behavioral options exist and if there is some means for these behavioral options to be transmitted across generations, then any behavior that has a slight advantage in terms of its effect on individual reproduction will increase in frequency.

Imagine that we have two different types of lions: some hunt prey by hiding in the brush, and others stand out in the open for all to admire their leonine majesty. Now suppose that each type produces offspring that use the same hunting strategy as their parents. If our ambushers do better than their nonambushing counterparts, ambush hunting behavior will be favored by natural selection and will, over time, increase in frequency. It is the same story with height; just replace height with ambush strategy.

It certainly seems reasonable to suggest that traits like height and hunting strategy are transmitted from one generation to the next by genes. Everyone knows that children look like their biological parents. Even if you have not taken a class in biology since high school, you know that this is so because parents pass their genes on to their offspring. But Darwin didn't know about genes when he published The Origin of Species in 1859. No one did. Until the turn of the twentieth century, the concept of genetic inheritance as we now understand it was not yet known by the vast majority of scientists. Nevertheless, once we found out the mechanisms of genetic inheritance, it made sense, at first glance, that these mechanisms would apply to all the traits Darwin thought were inherited.

Gregor Mendel, surely the most famous Austrian monk of all time, discovered the essential idea of the gene. He completed his simple and elegant experiments on the heredity of height in pea plants in 1865. Mendel's work was the start of the age of genetics, but despite the fact that Mendel did most of his work during the 1850s and 1860s, his findings were not disseminated until 1900. Darwin's grand theory predated the scientific community's understanding of what would be called the gene by forty years. In fact, the word gene was not used as a technical term for the unit of inheritance until 1909.

The story about genes and Darwin is strange. Not only was his theory of natural selection correct without precise information about genes; it was correct even though Darwin was just plain wrong about many aspects of inheritance. Darwin's ideas about how traits are passed down across generations focused on "gemmules." He believed that different parts of the body cast off many individual tiny particles -- gemmules, he called them -- that worked their way into sex cells. Then the gemmules originating in mother and father would blend together in offspring. Darwin, however, was wrong on two important counts. First, individual cells in the body don't cast off anything to sex cells, and, second, the units of inheritance (what Darwin called gemmules but we call genes) don't generally blend together and lose identity, but rather retain their integrity. Darwin, like virtually every other scientist of his time aside from Mendel, didn't grasp the basics of genetics as we understand it. It is a testament to the insight and sheer creativity of his theory of natural selection that it was developed in a genetic vacuum.

Once Mendel's discovery of the basic rules of inheritance was made and the term gene became common scientific parlance, genes quickly became thought of as the means by which traits could be transmitted across generations. We see this trend continuing today in research labs throughout the world as well as in the media in reports of genes for schizophrenia, genes for homosexuality, genes for alcoholism, and so on. Genes for this, genes for that. We live in a time when molecular biology seems to be front-page headline news almost every week.

If evolutionary biology as a discipline could be summarized in a single sentence, it would read something like this: Genes are selected to do whatever it takes to get copies of themselves into the next generation; everything else is just details. As such, natural selection works most efficiently and powerfully on behavioral traits directly linked to reproduction. Hence, one might think that if there is one time when genes would affect behavior most strongly, it would be during mating -- and so this is the behavior that we shall focus on primarily in this book.

There is no lack of genetic models of mate choice or data that support or fail to support these models, but one thing will become obvious once we work our way through genetic models of mate choice and empirical tests of these models: Despite being the framework for conceptualizing and analyzing mating for the past sixty years and despite the fact that genes clearly play a role in how animals choose their mates (and many of their other behaviors as well), the literature on genetic control of mating obviously cries out for more sophisticated approaches that take cultural variables due to imitation into account. Genetic models of mating assume that mate choice is completely beholden to genetic predispositions. They take as a given that females and males pay no attention to the actions of others in their population and don't change their behavior according to some simple cultural dictates. We now know that this is simply incorrect. Cultural rules matter -- and they matter a lot.

CULTURAL TRANSMISSION OF INFORMATION

Genes make copies of themselves and get those copies into the next generation. They affect behavior and, more particularly, mate choice behavior. They are a robust transmitter of information across generations. Another important means by which behavioral information can be transferred both within and between generations -- a means embraced by many psychologists since the inception of their field -- is the cultural transmission of information.

The notion that culture can play a role in nonhuman behavior goes back as least as far as Darwin's friend George Romanes. Romanes was one of the first psychologists to do detailed studies of animal intelligence, but for our purposes, his importance lies in the fact that he did pioneering work in the area of imitation, and his work showed that animals use techniques like imitation to transmit information.

There are literally hundreds of definitions of culture. The one you use depends on whether you are an anthropologist, psychologist, sociologist, or biologist, not to mention what subdiscipline you are in. Here, I view culture, and more specifically, cultural transmission of information, as involving some mix of trial-and-error learning, social learning via observation and imitation, and in special cases, teaching. Trial-and-error learning on its own does not constitute culture, because it does not include the transfer of information across individuals, which is a prerequisite for culture. For example, Ivan Pavlov, who introduced conditioned behavior to the world of psychology in the late 1800s (and won the Nobel prize in 1904), trained his dogs to learn that the sound of a bell meant food, but no information passed from dog to dog in these experiments. If one of Pavlov's dogs had taught another dog to pair the bell and food stimuli together, or even if one dog learned this from watching another dog being trained, then we would start talking about dog culture.

Culture itself can evolve in at least two different ways. First, there might actually be genes that code for cultural rules (let's call this type I cultural evolution). For example, imagine a gene with two variants (technically known as alleles). Variant 1 of our gene instructs individuals to imitate some behavior -- let's say food-gathering techniques -- that it sees others undertake; variant 2 does not code for imitation. If imitating others works better than not imitating, then we would expect variant 1 of the gene to start increasing in frequency through time. So the tendency to imitate spreads through a population. This can easily lead to very rapid changes in, say, food-gathering techniques -- changes that take place much faster than possible if none of our genes had coded for the possibility of imitation. More important, we shall see that even if genes do code for cultural rules, changes in behavior through time can be almost completely divorced from the genes that coded for culture to begin with.

The second way that cultural transmission can evolve is quite different from that already described in that it lacks any genetic underpinning to speak of. This sort of cultural evolution, which we'll call type II cultural evolution, works in a way analogous to genetic evolution, except using cultural rules, rather than genes, as the unit passed down across generations. Cultural norms that outcompete other norms (by increasing the reproductive success of those who adopt them) can spread through time, just as genes do. For example, suppose you are in a foreign land and are faced with a problem. Imagine you can adopt one of two cultural norms: "do as you always have done when facing similar problems" or "look around and adopt the behaviors used by locals." If the latter rule works better (that is, provides more benefits), and other individuals then learn this rule by either imitation or teaching, then cultural evolution will favor our "when in Rome" rule, and it will increase in frequency through time.

There are two absolutely critical differences between genetic evolution and cultural evolution. First, unlike genetic evolution, in the case of type II cultural evolution, behaviors can spread even if they don't necessarily provide benefits to the individuals adopting such norms. This can be a complicated process. Second, and more important, there are huge differences in the rate at which genetic and either type of cultural evolution operate. When genetic evolution operates quickly, we are usually talking about hundreds, if not thousands, of generations for natural selection to make a noticeable difference in most behaviors. In other scenarios, we might be talking about tens of thousands of generations for genetic evolution to create real change. Not so for cultural evolution, which can easily have a huge impact in just a handful of generations. In fact, cultural evolution can have a dramatic impact within a single lifetime.

In June 1836, Nathan Rothschild, arguably the richest man in the world at the time, left Frankfurt to attend the wedding of his son Lionel. He developed a boil and went to various doctors, but continued with his daily business, though the boil got worse and worse. By the end of July, Rothschild was dead. It is not clear whether the boil killed him or contamination from the knives of the surgeons who tried to lance it did him in, but that is beside the point. Rothschild lived 150 years ago -- roughly seven or eight human generations, or not nearly enough time for genetic evolution to affect our resistance to boils in any significant manner. But cultural evolution, with its mechanisms of education and imitation, in just the past generation has provided us with the medical knowledge to make the ailment that killed Rothschild a trivial medical problem in most places throughout the world. When it comes to the speed at which they operate, cultural evolution leaves genetic evolution in the dust.

Despite an obsession with the notion of culture and the importance of culture in shaping behavior, anthropologists and psychologists rarely develop models that make precise predictions about how cultural transmission will affect the distribution of any particular behavior over long periods of time. Such modeling has generally fallen on the shoulders of evolutionary biologists. The models recently developed by evolutionary biologists stand genetic models on their head and make all behavioral scientists rethink not only how culture operates with regard to a particular category of behavior such as mate choice, but to what extent culture can have a dramatic impact on simple animals with relatively small brains. Culture opens the door in these animals for the actions of a few to have serious consequences for the evolutionary trajectory of the many.

A number of different theoretical approaches have been employed to model the culture of mate choice or, more specifically, to model how females copy the choices of other females in their neighborhood. Certain corners of the animal kingdom capture aspects of all these theories, as we shall now see.

WHITE-BEARDED MANAKINS AND BLACK GROUSE

While studying the mating behavior of the white-bearded manakin bird in Trinidad in 1974, Alan Lill observed that a single male manakin on one breeding arena was obtaining more than 80 percent of all matings. Lill suggested that one explanation might be that females copy or imitate each other's choice of mates; that is, female mate preferences may be transmitted through a rudimentary form of culture.

Following Lill, many others have found that in birds and mammals that mate in arenas (also called leks), a single male often gets most of the matings, despite the presence of many other eligible males. Demonstrating that females were copying each other in such mating arenas, however, was very difficult, and the phenomenon remained largely anecdotal until the early 1990s, when a group of Scandinavian researchers, lead by Jacob Höglund, began a detailed study of mate copying in black grouse birds.

Surrounded by Scotch pine, Norway spruce, and birch, black grouse mating arenas are interspersed throughout the bogs of central Finland. As with manakins, a single "top male" grouse obtains about 80 percent of matings at an arena. Before mating, females visit arenas many times, and often in groups of females who stay together and synchronize their trips to various male territories at an arena. Hoglund and his colleagues observed that a male that had recently mated was likely to mate again sooner than by chance, suggesting a possible role for imitation. In addition, older females mated, on average, three days earlier than younger females, suggesting that copying, if it occurred, was most common among younger females. This is precisely what one would expect, as young and inexperienced females stand to gain much more from watching old pros than vice versa.

Höglund and his colleagues undertook an ingenious experiment using stuffed dummy females placed on male territories within a lek. In this experiment, seven males on a particular lek had stuffed black grouse dummies placed on their respective territories early in the morning, before females arrived. The males courted these dummy females and even mounted them and attempted numerous copulations. Their results indicate that females were more interested in a male with other (dummy) females on his territory. This finding is precisely what one would expect if copying, rather than some set of physical traits alone, explained the well-known skew in male reproductive success on black grouse leks.

Höglund's work, along with numerous other studies, will clearly demonstrate that there need not be a strong link between intelligence and culture. Creatures a quarter of an inch long may lack intelligence, but they don't lack a rudimentary form of culture. What matters is not brain size so much as the ability to incorporate what others are doing into one's behavioral repertoire.

THE GIRAFFE'S NECK

Recent work on cultural evolution breathes new life into one of the most controversial and demonized names in the history of biology: Jean-Baptiste de Lamarck (1744-1829). Despite his substantial reputation as a major botanist of his time, Lamarck's name is linked with one wrong-headed idea: the inheritance of acquired (physical) characteristics. This concept was part of Lamarck's grander "theory of transformation" and worked as follows: Individuals can cause a change in an organ through constant use, and that change (the newly acquired characteristic) can be passed on to the next generation.

The classic example used to illustrate Lamarck's idea is neck length evolution in giraffes. Standard natural selection models posit that natural variation in neck length would result in individuals with longer necks obtaining more food. If neck length was a heritable trait, those with longer neck lengths would produce more offspring, and through time the average neck length in a population would increase. Lamarck's theory, however, works quite differently. Under the inheritance of acquired characteristics model, giraffes, through constant use, might be able to stretch their necks a bit longer with practice. This new longer neck trait -- the result of constant attempts to reach food high in the trees -- is then passed on to offspring. In modern terms, what Lamarck was arguing is that simply using an organ causes it to change; this change affects the genetic underpinnings of the organ and is passed on to the next generation.

We now know that Lamarck's arrow of causality was pointing in the wrong direction. Although it is certainly possible, indeed likely, that use can change the structure of an organ in an individual, it does not feed back and actually change an individual's genetic makeup. Lamarck was simply wrong about acquired traits' changing the genetic structure in a way that can be passed down through generations. But although Lamarck was incorrect about acquired characteristics and genes, he was not wrong about acquired characteristics and evolution. Cultural evolution is fundamentally concerned with the acquisition of novel traits and passing on such acquired traits to the next generation. Given that no one of his time knew anything about genes, Lamarck's intuition is far less misguided than many have been led to believe in the twentieth century.

It is worth noting in passing that despite the fact that many of Darwin's ideas on natural selection are quite different from those of Lamarck with respect to how evolution proceeds, Darwin himself accepted Lamarck's ideas on the inheritance of acquired characteristics. In fact, Darwin, although he believed in the primacy of natural selection, felt strongly enough about Lamarck's ideas on acquired characteristics that he went to considerable trouble to show that they were not contrary to his own.

THE NATURE/NURTURE ASSUMPTION

The relationship between genetic and cultural evolution is not a rehashing of the highly politicized and murky "nature versus nurture" debate. To begin with, the nature versus nurture question has always been fuzzy in the sense that the fundamental terms in this debate -- nature and nurture -- cannot at this stage be usefully defined. Nature can mean either that (1) a trait is controlled at some level by a gene or a set of genes or (2) not only is a trait under genetic control, but many different variants of the genetic trait exist. If everyone had a gene that controlled the expression of behavior X, then we would be talking of "nature" in the former sense, but not the latter (since everyone has it, there is no genetic variation).

The same sort of ambiguity that we see for the term nature also holds true for nurture. In The Nurture Assumption, Judith Harris shows how nurture historically was thought to be synonymous with "parental environment," while her own work argues that the environment of the peer group is really where the nurture effects kick in. Fortunately, in discussing the interaction of genes and culture today, the scientific literature on both genetic and cultural evolution allows us to be quite precise in our definitions.

A further difference between the perspective taken here and that of the nature versus nurture debate centers on the distinction between individuals and populations. Nature versus nurture focuses on the individual -- for example, did someone fail (or succeed) because "nature" or "nurture" was the dominant factor? The genes and culture view presented here focuses on how individual behavior can have population-level changes over long periods of time. What's really interesting about this approach is recognizing that large-scale shifts occur because of genetic and cultural evolution in the landscape of life.

Nature and nurture are often depicted as discrete, mutually exclusive forces examined at one particular point in time. Genetic and cultural components to behavior, however, are both quite dynamic, shifting through time and capable of running away in very unexpected directions. Genes and culture can interact positively, or they may oppose one another. Either might overwhelm the other depending on conditions. None of these attributes has been part of the nature versus nurture controversy.

This is a golden age of theoretical biology, and Robert Boyd and Peter Richerson are among its leaders. In Culture and the Evolutionary Process, they note that biologists and anthropologists often ask, "Why not simply treat culture as a...response to environmental variation in which the 'environment' is the behavior of conspecifics?" That is, why not think of culture as just another means by which organisms adapt to the environment and leave it at that? Why all the hoopla? The reason is simple: cultural influences, unlike other environmental influences, are passed on from individual to individual. This means that the behavior of a single individual can potentially shift the behavior patterns seen in an entire population, all in the time span of less than a lifetime. That makes all the difference.

THE REAL CULTURE WAR

Historically, evolutionary biologists have been quite leery of adopting the notion that culture is important in understanding behavior in animals. In fact, many prominent evolutionary biologists are still leery of divorcing any behavior completely from genes, even in humans. Richard Dawkins became a giant of the history of biological science in the latter half of the twentieth century for his idea of the selfish gene, which says, in effect, that we are all gene robots. All animal behavior can be explained through the genetic imperative to replicate genes. He has argued for decades that virtually all of what we see, in both animals and humans, can be tied back to the genes. Genes, the argument goes, have deceptively long reaches, so that the abodes that animals (including humans) live in, their more complex behavioral traditions, and even their personalities, while appearing somehow to be divorced from genes, really are not. The power of the gene, so it is argued, works indirectly to produce all of these phenomena. Culture, then, is just genes working behind the scenes -- and that's it. To be fair to Dawkins, he has softened his view on this point somewhat by exploring his concept of a discrete cultural unit he dubbed the meme (and which we shall examine in much greater detail in Chapter 5), but many behavioral biologists dogmatically hold his pre-meme views; and, after all, the meme still plays second fiddle to the gene in Dawkins's orchestra of life.

This skeptical response to the contention that culture is a powerful evolutionary force, in everything from simple to complex life forms, is in its own right due to many factors, not the least of which is the lack of a sound theoretical framework for understanding how culture can operate across long periods of evolutionary time. In the last twenty years or so, thanks to a handful of evolutionary biologists, such a framework for understanding the evolution of culture has emerged. This theoretical revolution has led empiricists studying the evolution of behavior to change their view of how behavior evolves and to design new studies to address behavior and transmission.

In addition to the emerging acceptance of two means for transmitting information -- genes and culture -- there have been new theoretical advances that examine when one might expect each of these transmission modes to be most prevalent. These models generally predict that genetic transmission will be most efficient in stable environments. When the capacity for culture exists, however, it will be a particularly efficient means of transmitting information about behavior in environments that are in constant change. The logic of this finding is simple. When things stay relatively stable, a fixed means of transferring information (one that does not rely on the vagaries of learning from others) will be selected; hence the success of genes in such environments. When the world around us is constantly changing, in both the short and the long haul, some means that can allow for new rules and innovations (even with the associated costs of making errors) works best. Hence, cultural transmission should be most prevalent in these environments.

INTERACTION, INTERACTION, INTERACTION

Cultural and genetic evolution interact in bizarre ways. These two forces may act in the same direction, or they may conflict with one another. Interactions in which genes or culture or some combination of the two win the day are all possible. Genes may even code for culture, but the manifestations of such culture -- for example, fads and crazes -- cannot be measured in any meaningful way by studying genetic architecture.

In their dual inheritance models, theoreticians Boyd and Richerson argue that all of the forces that lead to changes in gene frequencies have analogues within the realm of cultural evolution. Their models demonstrate how cultural change can be studied with techniques similar to those developed by population geneticists. Furthermore, they demonstrate how cultural evolution and genetic evolution can operate in the same or opposite directions, and how either can be the predominant force, depending on the particular scenario.

According to Boyd and Richerson's theory, examining cultural and genetic influences on mate choice independently only sets the stage for the $64,000 question: How do genes and culture interact, either cooperatively or competitively, to shape behavior? And under what conditions do we expect cultural influences to outweigh genetic factors, and vice versa? To address these issues, we will examine two very different modes by which genes and culture potentially interact. On the one hand, genetic evolution and cultural evolution may be two distinct processes that either reinforce one another or are in opposition. A more indirect and complicated means by which genes and culture may interact is that genes may actually code for cultural norms, allowing for some adaptive behaviors to spread quickly through a population. While this causes the distinction between these processes to blur somewhat, it also produces the bizarre possibility that genes code for culture and yet culture may produce behavior different from try, examining cultural and genetic influences on mate choice independently only sets the stage for the $64,000 question: How do genes and culture interact, either cooperatively or competitively, to shape behavior? And under what conditions do we expect cultural influences to outweigh genetic factors, and vice versa? To address these issues, we will examine two very different modes by which genes and culture potentially interact. On the one hand, genetic evolution and cultural evolution may be two distinct processes that either reinforce one another or are in opposition. A more indirect and complicated means by which genes and culture may interact is that genes may actually code for cultural norms, allowing for some adaptive behaviors to spread quickly through a population. While this causes the distinction between these processes to blur somewhat, it also produces the bizarre possibility that genes code for culture and yet culture may produce behavior different from that predicted in the presence of genes alone.

Data now emerging show the fascinating and unexpected ways that genes and culture actually interact in animal mating situations. Consider the case of a fish less than an inch long: the guppy. In this species, females have an innate preference for males with lots of orange body color. Combining the importance of female mate copying with the documented genetically based preferences that female guppies exhibit for colorful males creates an ideal system in which to examine the relative importance of genetic and cultural factors in shaping female mate choice. In a 1996 experiment in my lab, I did just that. Essentially I created an evolutionary soap opera. A female's genetic predisposition was "pulling" her toward a more orange male, but social cues and the potential to copy the choice of others was tugging her in the exact opposite direction -- toward the drabber of two males. When males differed by small amounts of orange, females consistently chose the less orange males. In other words, they copied the choice of a female placed near such a male. Here, culture -- in this case, the tendency to copy mate choice -- overrode a genetic predisposition for orange males. If, however, males differed by large amounts of orange, females ignored the choice of others and preferred the oranger males -- in this case, genetic predisposition masked any cultural effects. With guppies, it is as if a threshold color difference exists between males in the eyes of female guppies. Below that threshold, cultural effects are predominant in determining female mate choice, and above that threshold genetic factors cannot be overridden -- and this in fish with a brain the size of a pinhead!

In order to examine how genes and culture work together, we will begin by examining genetic and cultural elements in isolation. And to see why "selfish gene" models have made a major contribution to our understanding of the evolution of behavior, but fail to capture the importance of cultural evolution in animals and humans, it is necessary to devote the next chapter to the genetic models that have been used to describe the way individuals select mates.

Copyright © 2000 by Lee Alan Dugatkin

Edition details

• Publisher: Free Press
• Publication date: 2001
• Language: English
• ISBN 10: 0684864533
• ISBN 13: 9780684864532
• Binding: Hardcover
• Edition number: 1
• Number of pages: 256