Natural selection and adaptation relationship memes

Abstract. The concept of cultural evolution is central to any discussion of “memes” . Hence the relationship between structure and function can be . Although it was not discussed in Adaptation and Natural Selection, this was the background . Darwinian paradigm of natural selection for morality .. Apparently, there is a world of difference between a or kin selection theory, relatives or kin could be e . mission of memes is still at an early stage and is zees and 80% in humans. Memes appeared in human evolution when our ancestors became capable . the “be-all and end-all of evolution which all adaptations could be said to . relationship” (Plotkin , p ), while Wilson defines the natural.

For example, oyster catchers use two different methods for opening mussels according to local tradition but the two methods do not compete in the same population — in other words there is no differential selection of variants within a given population. Tomasello, Kruger and Ratner argue that many chimpanzee traditions are also of this type. Although the behaviours are learned population-specific traditions they are not cultural in the human sense of that term because they are not learned by all or even most of the members of the group, they are learned very slowly and with wide individual variation, and — most telling — they do not show an accumulation of modifications over generations.

There may be exceptions to this. For example, individuals in the same group use two different methods for catching ants on sticks, and several ways of dealing with ectoparasites while grooming. However, they suggest that these require true imitation for their perpetuation.

Imitation True imitation is more restrictively defined, although there is still no firm agreement about the definition see ZentallWhiten This means that one animal must acquire a novel behaviour from another — so ruling out the kinds of contagion noted above.

Whiten and Hamwhose definition is widely used, define imitation as learning some part of the form of a behaviour from another individual. Similarly Heyes distinguishes between true imitation — learning something about the form of behaviour through observing others, from social learning — learning about the environment through observing others thus ruling out stimulus and local enhancement.

True imitation is much rarer than individual learning and other forms of social learning. Humans are extremely good at imitation; starting almost from birth, and taking pleasure in doing it. Meltzoff, who has studied imitation in infants for more than twenty years, calls humans the consummate imitative generalist Meltzoff, although some of the earliest behaviours he studies, such as tongue protrusion, might arguably be called contagion rather than true imitation.

Just how rare imitation is has not been answered. There is evidence of imitation in the grey parrot and harbour seals. Many experiments have been done on imitation and although they have not been directly addressed at the question of whether a new replicator is involved, they may help towards an answer.

For example, some studies have tried to find out how much of the form of a behaviour is copied by different animals and by children. In the two-action method a demonstrator uses one of two possible methods for achieving a goal such as opening a specially designed containerwhile the learner is observed to see which method is used Whiten et al.

If a different method is used the animal may be using goal emulation, but if the same method is copied then true imitation is involved. Evidence of true imitation has been claimed using this method in budgerigars, pigeons and rats, as well as enculturated chimpanzees and children Heyes and Galef Other studies explore whether learners can copy a sequence of actions and their hierarchical structure Whiten Byrne and Russon distinguish action level imitation in which a sequence of actions is copied in detail from program level imitation in which the subroutine structure and hierarchical layout of a behavioural program is copied.

They argue that other great apes may be capable of program level imitation although humans have a much greater hierarchical depth. Such studies are important for understanding imitation, but they do not directly address the questions at issue here — that is, does the imitation entail an evolutionary process?

Is there a new replicator involved? To answer this we need new kinds of research directed at finding out whether a new evolutionary process is involved when imitation, or other kinds of social learning, take place. This might take two forms. First there is the question of copying fidelity. As we have seen, a replicator is defined as an entity that passes on its structure largely intact in successive replications.

So we need to ask whether the behaviour or information is passed on largely intact through several replications. For example, in the wild, is there evidence of tool use, grooming techniques or other socially learned behaviours being passed on through a series of individuals, rather than several animals learning from one individual but never passing the skill on again?

In experimental situations one animal could observe another, and then act as model for a third and so on as in the game of Chinese whispers or telephone. We might not expect copying fidelity to be very high, but unless the skill is recognisably passed on through more than one replication then we do not have a new replicator — i.

Second, is there variation and selection? The examples given by Whiten et al. We might look for other examples where skills are passed to several individuals, these individuals differ in the precise way they carry out the skill, and some variants are more frequently or reliably passed on again.

For this is the basis of cumulative culture.

Natural Selection and the Rock Pocket Mouse — HHMI BioInteractive Video

Experiments could be designed to detect the same process occurring in artificial situations. Such studies would enable us to say just which processes, in which species, are capable of sustaining an evolutionary process with a new replicator. Only when this is found can we usefully apply the concept of the meme.

If such studies were done and it turned out that, by and large, what we have chosen to call imitation can sustain cumulative evolution while other kinds of social learning cannot, then we could easily tie the definitions of memes and imitation together — so that what counts as a meme is anything passed on by imitation, and wherever you have imitation you have a meme. In the absence of such research we may not be justified in taking this step, and some people may feel that it would not do justice to our present understanding of imitation.

Nevertheless, for the purposes of this paper at least, that is what I propose. This allows me to draw the following conclusion. Imitation is restricted to very few species and humans appear to be alone in being able to imitate a very wide range of sounds and behaviours. This capacity for widespread generalised imitation must have arisen at some time in our evolutionary history. When it did so, a new replicator was created and the process of memetic evolution began. This, I suggest, was a crucial turning point in human evolution.

I now want to explore the consequences of this transition and some of the coevolutionary processes that may have occurred once human evolution was driven by two replicators rather than one.

One consequence, I suggest, was a rapid increase in brain size. The big human brain Humans have abilities that seem out of line with our supposed evolutionary past as hunter-gatherers, such as music and art, science and mathematics, playing chess and arguing about our evolutionary origins. This problem led Wallace to argue, against Darwin, that humans alone have a God-given intellectual and spiritual nature see Cronin Humans have an encephalisation quotient of about 3 relative to other primates.

That is, our brains are roughly three times as large when adjusted for body weight Jerison The increase probably began about 2. Not only is the brain much bigger than it was, but it appears to have been drastically reorganised during what is, in evolutionary terms, a relatively short time Deacon Nevertheless, the human brain stands out. The problem is serious because of the very high cost in energy terms of both producing a large brain during development, and of running it in the adult, as well as the dangers entailed in giving birth.

Chimpanzees live in complex social groups and it seems likely that our common ancestors did too. Making and breaking alliances, remembering who is who to maintain reciprocal altruism, and outwitting others, all require complex and fast decision making and good memory. Other theories emphasise the role of language DeaconDunbar There are three main differences between this theory and previous ones. First, this theory entails a definite turning point — the advent of true imitation which created a new replicator.

On the one hand this distinguishes it from theories of continuous change such as those based on improving hunting or gathering skills, or on the importance of social skills and Machiavellian intelligence. Second, both Donald and Deacon emphasise the importance of symbolism or mental representations in human evolution.

Other theories also assume that what makes human culture so special is its symbolic nature. This emphasis on symbolism and representation is unnecessary in the theory proposed here. Whether behaviours acquired by imitation i. All that matters is whether they are replicated or not. Third, the theory has no place for the leash metaphor of sociobiology, or for the assumption, common to almost all versions of gene-culture coevolution, that the ultimate arbiter is inclusive fitness i.

In this theory there are two replicators, and the relationships between them can be cooperative, competitive, or anything in between. Most important is that memes compete with other memes and produce memetic evolution, the results of which then affect the selection of genes.

On this theory we can only understand the factors affecting gene selection when we understand their interaction with memetic selection. In outline the theory is this. The turning point in hominid evolution was when our ancestors began to imitate each other, releasing a new replicator, the meme. Memes then changed the environment in which genes were selected, and the direction of change was determined by the outcome of memetic selection.

Among the many consequences of this change was that the human brain and vocal tract were restructured to make them better at replicating the successful memes. The origins of imitation We do not know when and how imitation originated. In one way it is easy to see why natural selection would have favoured social learning.

Mathematical modelling has shown that this is worthwhile if the environment is variable but does not change too fast Richerson and Boyd Similar analyses have been used in economics to compare the value of costly individual decision making against cheap imitation Conlisk As we have seen, other forms of social learning are fairly widespread, but true imitation occurs in only a few species. Moore compares imitation in parrots, great apes and dolphins and concludes that they are not homologous and that imitation must have evolved independently at least three times.

In birds imitation probably evolved out of song mimicry, but in humans it did not. The latter sounds very difficult to achieve — involving transforming the visual input of a seen action from one perspective into the motor instructions for performing a similar action oneself. However, mirror neurons in monkey premotor cortex appear to belong to a system that does just this. The same neurons fire when the monkey performs a goal-directed action itself as when it sees another monkey perform the same action, though Gallese and Goldman believe this system evolved for predicting the goals and future actions of others, rather than for imitation.

Given that mirror neurons occur in monkeys, it seems likely that our ancestors would have had them, making the transition to true imitation more likely.

We also do not know when that transition occurred. The first obvious signs of imitation are the stone tools made by Homo habilis about 2. It seems likely that less durable tools were made before then; possibly carrying baskets, slings, wooden tools and so on. Even before that our ancestors may have imitated ways of carrying food, catching game or other behaviours. By the time these copied behaviours were widespread the stage was set for memes to start driving genes.

I shall take a simple example and try to explain how the process might work. Memetic drive Let us imagine that a new skill begins to spread by imitation. This might be, for example, a new way of making a basket to carry food.

The innovation arose from a previous basket type, and because the new basket holds slightly more fruit it is preferable. Other people start copying it and the behaviour and the artefact both spread. Note that I have deliberately chosen a simple meme or small memeplex to illustrate the principle; that is the baskets and the skills entailed in making them. In practice there would be complex interactions with other memes but I want to begin simply.

Now anyone who does not have access to the new type of basket is at a survival disadvantage. A way to get the baskets is to imitate other people who can make them, and therefore good imitators are at an advantage genetically. This means that the ability to imitate will spread. If we assume that imitation is a difficult skill as indeed it seems to be and requires a slightly larger brain, then this process alone can already produce an increase in brain size.

This first step really amounts to no more than saying that imitation was selected for because it provides a survival advantage, and once the products of imitation spread, then imitation itself becomes ever more necessary for survival. This argument is a version of the Baldwin effect which applies to any kind of learning: So this is not specifically a memetic argument. However, the presence of memes changes the pressures on genes in new ways. The reason is that memes are also replicators undergoing selection and as soon as there are sufficient memes around to set up memetic competition, then meme-gene coevolution begins.

Let us suppose that there are a dozen different basket types around that compete with each other. Now it is important for any individual to choose the right basket to copy, but which is that? Since both genes and memes are involved we need to look at the question from both points of view.

This will probably be the biggest, strongest, or easiest basket to make. People who copy this basket will gather more food, and ultimately be more likely to pass on the genes that were involved in helping them imitate that particular basket. In this way the genes, at least to some extent, track changes in the memes. These memes spread whenever they get the chance, and their chances are affected by the imitation skills, the perceptual systems and the memory capacities among other things of the people who do the copying.

Now, let us suppose that the genetic tracking has produced people who tend to imitate the biggest baskets because over a sufficiently long period of time larger artefacts were associated with higher biological success. This now allows for the memetic evolution of all sorts of new baskets that exploit that tendency; especially baskets that look big. They need not actually be big, or well made, or very good at doing their job but as long as they trigger the genetically acquired tendency to copy big baskets then they will do well, regardless of their consequence for inclusive fitness.

The same argument would apply if the tendency was to copy flashy-looking baskets, solid baskets, or whatever.

  • Cultural Evolution

So baskets that exploit the current copying tendencies spread at the expense of those that do not. This memetic evolution now changes the situation for the genes which have, as it were, been cheated and are no longer effectively tracking the memetic change. Now the biological survivors will be the people who copy whatever it is about the current baskets that actually predicts biological success. This might be some other feature, such as the materials used, the strength, the kind of handle, or whatever — and so the process goes on.

This process is not quite the same as traditional gene-culture evolution or the Baldwin effect. The baskets are not just aspects of culture that have appeared by accident and may or may not be maladaptive for the genes of their carriers.

They are evolving systems in their own right, with replicators whose selfish interests play a role in the outcome. I have deliberately chosen a rather trivial example to make the process clear; the effects are far more contentious, as we shall see, when they concern the copying of language, or of seriously detrimental activities. Whom to imitate Another strategy for genes might be to constrain whom, rather than what, is copied. For example, a good strategy would be to copy the biologically successful.

People who tended, other things being equal, to copy those of their acquaintances who had the most food, the best dwelling space, or the most children would, by and large, copy the memes that contributed to that success and so be more likely to succeed themselves. In this situation as I have suggested above success is largely a matter of being able to acquire the currently important memes.

So this strategy amounts to copying the best imitators. I shall call these people meme fountains, a term suggested by Dennett to refer to those who are especially good at imitation and who therefore provide a plentiful source of memes — both old memes they have copied and new memes they have invented by building on, or combining, the old. Any memes that got into the repertoire of a meme fountain would thrive — regardless of their biological effect. The meme fountain acquires all the most useful tools, hunting skills, fire-making abilities and his genes do well.

However, his outstanding imitation ability means that he copies and adapts all sorts of other memes as well. These might include rain dances, fancy clothes, body decoration, burial rites or any number of other habits that may not contribute to his genetic fitness. Since many of his neighbours have the genetically in-built tendency to copy him these memes will spread just as well as the ones that actually aid survival.

Whole memetic lineages of body decoration or dancing might evolve from such a starting point. Taking dancing as an example, people will copy various competing dances and some dances will be copied more often than others. This memetic success may depend on whom is copied, but also on features of the dances, such as memorability, visibility, interest and so on — features that in turn depend on the visual systems and memories of the people doing the imitation.

As new dances spread to many people, they open up new niches for further variations on dancing to evolve. Any of these memes that get their hosts to spend lots of time dancing will do better, and so, if there is no check on the process, people will find themselves dancing more and more. Dancing cannot now be un-evolved but its further evolution will necessarily be constrained.

Someone who could better discriminate between the useful memes and the energy-wasting memes would leave more descendants than someone who could not. So the pressure is on to make more and more refined discriminations about what and whom to imitate. And — crucially — the discriminations that have to be made depend upon the past history of memetic as well as genetic evolution.

If dancing had never evolved there would be no need for genes that selectively screened out too much dance-imitation. Since it did there is. This is the crux of the process I have called memetic driving. The past history of memetic evolution affects the direction that genes must take to maximise their own survival. We now have a coevolutionary process between two quite different replicators that are closely bound together.

To maximise their success the genes need to build brains that are capable of selectively copying the most useful memes, while not copying the useless, costly or harmful ones. The result is a mass of evolving memes, some of which have thrived because they are useful to the genes, and some of which have thrived in spite of the fact that they are not — and a brain that is designed to do the job of selecting which memes are copied and which are not.

This is the big human brain. Its function is selective imitation and its design is the product of a long history of meme-gene coevolution. Whom to mate with There is another twist to this argument; sexual selection for the ability to imitate. They are also domains where some change is adaptive, leading to an improved handling of environmental pressures and opportunities. On the biological side, enormous progress was made though Darwin's realization that variation, heredity and differential reproduction can produce not only adaptive change, but also entirely new forms of life.

Darwinism and cultural change

Although analogies between biological and cultural change have long been noted, recent work has given them a new role. Especially since the arguments of Tomasello [ 1 ], the trans-generational accumulation of knowledge and skills by some form of cultural transmission has become an important element in explanations of the unusual course taken by human evolution over the past 2 Myr.

This phenomenon is, I suggest, both especially important and underappreciated in the case of cultural evolution. I begin with the case of biological evolution, and look at how different theoretical ideas get purchase at three different grains of description.

The application of different Darwinian ideas also requires attention to exactly what is being explained—the origination of variants, or changes to distributions in a population.

Cultural Evolution (Stanford Encyclopedia of Philosophy)

Yet attractors can also be more local, corresponding to more narrowly shared cognitive dispositions or biases, common only to small communities. Such dispositions can explain reproduction that is only reliable across narrowly specified cultural contexts.

Work in this tradition e. Morin aims to answer the charge that the cultural evolutionary approach is vacuous via the detailed delineation of such factors of attraction, and their populational consequences, at various spatial and temporal scales.

Cumulative Culture Some theorists begin their presentations of cultural evolutionary theory by arguing that cultural change meets the conditions for evolution by natural selection stressed by Darwin. They argue, for example, that in the realm of culture we find ample variation—there are alternative ways of making pots, alternative designs for kayaks, and so forth—that there are differences in the likelihood of these variants being preserved or multiplied in future generations—dependent on whether the pots in question look attractive, whether the different forms of kayak are easy to handle—and that there is adequately faithful reproduction as these techniques or designs travel from one individual to another.

In other words, we find some version of variation, differential fitness and inheritance instantiated in the cultural context, as well as in the organic realm that Darwin primarily focused on. One of the risks of approaching the cultural evolution project in this abstract manner, which begins with the hunt for general similarities between the cultural and organic domains, has already been touched on.

While we secure the general claim that a form of natural selection applies in the cultural domain, we can lose sight of what specific explanatory problems a theory of cultural evolution is supposed to address. As we have seen, other presentations of cultural evolution begin in a more pragmatic, problem-driven fashion. In some cases they begin with explanatory puzzles similar to those that led Darwin to formulate his principle of natural selection in the first place. Darwin was concerned to explain how structures could arise which fit organisms so remarkably well to their conditions of existence.

Cultural evolutionists frequently draw attention to a variety of adaptive cultural traits, whose origination seems inexplicable in terms of individual innovation alone. Henrich97—for example, makes good use of the example of manioc processing. Manioc also called cassava is a good source of starch, but it needs to be processed to make it safe to eat. Without this processing it can release poisonous hydrogen cyanide.

What is more, while unprocessed manioc tastes bitter, the bitter taste is not a good indicator of its safety: Worse, while unprocessed manioc is poisonous, it is hard to discover that this is the case, because the symptoms of poisoning only appear well after eating unsafe manioc.

Henrich argues that it is hard to see how any single insightful individual could have invented this processing technology. Instead, a more gradual process of cumulative cultural adaptation, spread across the population, must be invoked. In other words, the rationale for turning to selection is the same in both the cultural and organic domains.

As Darwin noted, humans are regularly moved to act in ways that benefit others, even when those others are not members of extended families. This explanation has been updated across a long series of publications by Richerson, Boyd and others, who also aim to explain the very widespread tendencies of modern humans to share valuable resources across broad social networks e. Richerson and BoydRicherson et al Their view is that the resources of more mainstream evolutionary theory are not up to this explanatory task.

Kin selection is insufficient, they say, because humans regularly share with people outside their immediate family groups. Moreover, they take the view that the Pleistocene social groups in which they believe these sharing behaviours evolved were probably too large for reciprocal altruism to explain their emergence. Once cultural transmission has established this social environment, natural selection acting on genetic variation then favours an innate psychology that is suited to this new, socially-inherited set of environmental problems.

The very idea of group selection is a controversial one. Many commentators have taken a sceptical view of group selection when underpinned by genetic inheritance, because of worries that competition based on genetic variation within groups will tend to undermine the effects of competition between groups.

Darwinism and cultural change

Several cultural evolutionists e. Boyd and RichersonHenrich have argued that cultural inheritance processes are better able than processes of genetic inheritance to sustain between-group differences, for they believe there is good empirical and theoretical evidence that cultural processes can maintain within-group homogeneity in the face of various countervailing factors immigration, unreliable imitation and so forth.

Needless to say, this work is contentious. It is possible to challenge the claims made about the innateness of the social psychological dispositions in question, the characterisation of likely Pleistocene social groups, the inability of more traditional evolutionary resources to explain our altruistic tendencies, and so forth see Birch Such challenges are inevitable when a hypothesis is as ambitious as this one, and when it draws on such a variety of supporting sources of data.

There are also conceptual concerns. A recent paper lists three different forms of cultural group selection, of which straightforward competition between groups is just one variant Richerson et al. The authors also offer selective imitation by individuals of individuals in successful groups, and selective migration by individuals into successful groups, as two further types of cultural group selection.

These are indeed additional ways by which behavioural traits that are of benefit to a group can increase in frequency in a larger population of groups. Because of this, thinking of them as forms of group selection may introduce confusion see also Morin Regardless of these worries, it is clear that the cultural group selection explanation for forms of altruistic behaviour marks a significant effort to synthesise theory and evidence across a wide set of domains.

Evolvability A closely related way to vindicate models of cultural evolution looks to the question of the general features of inheritance systems that make for evolvability in a lineage. This project has been pioneered in recent years by Kim Sterelny e. Once again, let us illustrate the general nature of these issues by beginning in the organic realm. The basic conditions for natural selection do not, in spite of appearances, suffice for the appearance of functional traits. A system in which offspring resemble parents with respect to fitness-enhancing traits may not develop complex adaptations.

The environment needs to cooperate: If ontogeny is set up in such a way that changes to any one trait tend to be accompanied by changes to all other traits, then the chances are that cumulative adaptation will be particularly hard to come by. For even in those cases where a mutation contributes positively to the function of one trait, the chances are that it will contribute negatively to overall fitness in virtue of its disruption of the functioning of other traits.

Development also needs to make a wide range of variation available. If it is highly constrained, so that only a small number of forms are possible, then selection is not presented with a broad enough range of raw materials from which to fashion complex traits.

This occurs when individual organisms go it alone, sabotaging complex features of group organisation in favour of their own fitness. Individual-level selection, in contrast, can build individual-level adaptations. By applying these sorts of considerations to the cultural realm we can attempt to understand the likely costs and benefits associated with various different forms of cultural inheritance vertical, oblique, meme-like and so forth.

We can also perhaps come to an understanding of the different evolutionary forces that might bring these different forms of cultural inheritance into existence.

And, in turn, these insights may facilitate comparative work that seeks to document the general conditions that are required for a species to make use of cultural inheritance in order to build complex adaptations such as tools. This way of thinking offers the promise, for example, of explaining why few, if any, non-human species are able to build progressively more and more complex cultural features in a cumulative manner Richerson and Boyd; see also Laland The exploration of the significance of these conditions in the cultural realm is contentious, partly because the conditions for evolvability themselves are disputed see Godfrey-Smith Questions relating to evolvability are also tied up with difficult issues relating to the units-of-selection debate Okasha Does something like this occur in the cultural realm?

Does selection on human groups act so as to limit the ability of individual humans to go it alone? In what ways might cultural inheritance be involved in these processes? These questions are complex, both in terms of how they should be posed and how they should be answered. But some of the most interesting work in cultural evolutionary theory may come from efforts to answer them. Issues relating to evolvability are sometimes framed in terms of systems of information transfer.

On this view, if offspring are to resemble parents, developmental information must be transmitted from one generation to the next. The question is what forms of information transmission system do this job.

natural selection and adaptation relationship memes

This mode of framing the issue is contentious, for it is not always clear how we are to understand the concept of information, and what it means for some causal contributor to development to count as an information-bearer, rather than some other kind of developmental participant, such as an information-reader, say, or a background condition for information transfer see Oyama and Griffiths for discussion of these issues.

Maynard Smith and Szathmary propose that we can think of these events as modifications to the mechanisms of inter-generational information transmission.

Jablonka and Lamb argue that thinking in terms of information transmission systems also allows us to point out salient differences in the forms of social transmission underlying cultural evolution. They claim that only some forms of social transmission make use of a system of symbols. Consider, for example, that to say that some birds inherit their song by social transmission is not to say that birdsong is a symbolic system.

Humans, on the other hand, trade in publicly-accessible symbols. Moreover, repositories of symbols, most obviously in the form of libraries and computer databases, are vital inheritance systems for humans, allowing the preservation and accumulation of knowledge across generations.

Note, also, that there are different types of symbol system. In some cases the relationship between a symbol and what is represented is arbitrary.

natural selection and adaptation relationship memes

In other cases of iconic symbolism, the relationship is one of resemblance: Jablonka and Lamb use the characteristic differences between typical modes of social inheritance in animals and humans to illuminate the impact our own symbolic transmission systems have on human cultural evolution see also Deacon Although they argue that there can be non-linguistic symbolic systems, language exemplifies nicely the way in which systems of symbols contain elements that can be recombined in countless ways to yield a vast array of different meaningful messages.

Repositories of symbolically stored information, such as books, can also be searched, annotated, edited and so forth, in ways that add to their power and versatility. This manner of thinking opens up a number of challenging issues. The question of the degree to which symbolic systems resemble other inheritance systems is an illuminating one.

One quickly realises that any attempt to say precisely what makes some inheritance system a symbolic system, and any attempt to differentiate between types of symbolic systems linguistic, non-linguistic and so forthwill be exceptionally philosophically demanding.

Cultural Phylogenies Many evolutionists have argued that biological tools can have great value when we wish to develop a historical view of the pattern of cultural change see, for example, Gray at alMace and Holden A variety of biological methods have been developed that help us to uncover the structure of evolutionary trees: It seems clear that cultural items of many kinds most obviously languages, but also tools and techniques also stand in recognizable genealogical relationships, and this has led many biological anthropologists to use phylogenetic methods borrowed or adapted from the biological sciences in order to reconstruct the history of borrowings in the cultural realm.

Critics have sometimes followed Gould in arguing that these biological methods cannot be properly applied to the cultural realm, because cultural genealogies take the form of reticulated networks, rather than branching trees.

Cultural change is indeed often highly reticulated: Moreover, as improvements are made to cars these new developments may be borrowed by innovators of bicycles, furniture, toys and other shifting constellations of artifacts. These important observations need not undermine the project of cultural phylogeny. Much of biological evolution is also reticulated. Bacteria, for example, do not form genealogically isolated lineages, hybridization is rife among plants, and there is also considerable borrowing of elements of the genome between apparently isolated mammalian species.

Of course this might show simply that phylogenetic modes of inference are doubly imperilled: But cultural evolutionists e. Gray et al are encouraged by inferential developments within biology itself, which aim to reconstruct partially reticulated trees by proposing so-called reconciliations of the conflicting trees that traditional methods often propose for species and genes.

This kind of work is important, in part because of the uses to which well-confirmed cultural phylogenies can be put. It may be easiest to illustrate their value via a simple example. On the face of things, looking for correlations is a reasonable albeit fallible way to discover causal relationships. If, for example, people who smoke often get lung cancer, and people with lung cancer are often smokers, then we have good evidence that smoking causes lung cancer or perhaps that lung cancer causes smoking.

But there can be strong correlations that do not indicate causation. If, for example, we find that there is a strong correlation in animals between making a moo sound and producing large quantities of milk, we should not conclude that one causes the other.

Mooing and milk production go together because the creatures in question share ancestors in common, who both mooed and gave lots of milk. Of course, in the case of cows this fact of common ancestry is so obvious that we hardly notice how it informs our causal inference.

But cultural phylogenies are unobvious. Russell Gray, among others, has long argued that when we understand them better, our knowledge of phylogenies can then confirm, or undermine, causal hypotheses that are claimed on the basis of correlation. Gray and Wattsfor example, have scrutinised what is sometimes called the Supernatural Punishment Hypothesis. This is the hypothesis that belief in powerful gods, who inflict punishment on wrongdoers, tends to result in societies that are better able to harness the fruits of cooperation see Norenzayan et al We must also take into account the potentially confounding consequences of shared ancestry among the societies surveyed.

Gray and Watts draw on Austronesian data to argue that belief in moralising high gods tends to be gained after, not before, the emergence of political complexity; so these data, they suggest, undermine the thought that moralising high gods drive this form of complexity. That said, they do find some support for a weaker supernatural punishment hypothesis based on belief in punishment interventions from natural spirits, ancestral spirits and mythical heroes, as well as from moralising high gods.

Work such as this indicates the potential for cultural phylogenetics to inform broad-sweep hypotheses about not just the patterns, but also the causal processes, that have marked the cultural history of our species. Individual learning refers to situations in which individuals learn by observing or interacting directly with their environment In a species like ours it is hardly ever the case that what an individual learns is free from influence by others. The structures and contents of our dwellings and workplaces, the constitutions of the domesticated plants and animals we interact with, the cultivated and engineered environments we live in, all have been affected by the activities of our predecessors.

The overlap between individual and social forms of learning has significance for research on non-human, as well as the human, species. The group of wild chimpanzees studies by Hobaiter et al began to develop a new behaviour: Some then began to make these sponges from moss instead.

The researchers saw one individual develop this behaviour because she re-used an old moss sponge, which had previously been discarded by another chimp. But she did not do this because she had seen the sponge in use.

One the one hand, this is a clear case of individual learning: As that distinction blurs, so the further question of what culture consists in becomes less clear Lewens For there are numerous ways in which activities of one generation can, by altering or maintaining stable features of biotic, social and technical environments, have an influence over what individuals in the following generations end up learning.

These phenomena are recognised by many prominent theorists of cultural evolution. Laland et al stress this theme in their work on niche-construction—i. Critics of these final comments e. Clarke and Heyes have urged that we seek more detailed information concerning whether individual learning—which, as we have seen, can take place in felicitously structured environments—truly is less sophisticated than forms of learning that attend directly to the behaviours of others.

We need to ask both whether there is an additional form of sophistication in the cognitive mechanisms that underpin social compared with individual learning, and also whether social learning has greater functionality, specifically with respect to the generation of increasingly refined behaviours, technologies, norms and institutions across populations.

These are just the types of questions to which the methods of cultural evolutionary work—which combine populational modelling with work in cognitive science—are well placed to give answers. University of Chicago Press. Universal Acid or a Better Mousetrap? Oxford University Press, pp. A Quantitative Approach, Princeton: Harvard University Press, The Lamarckian Dimension, Oxford: