Figure 5.1 Logic task (adapted from J. Strangroom, 'The Wason Selection Task', Philosophy Experiments, 2014, www.philosophyexperiments.com/wason/default.aspx (accessed 17 June 2014)).
Jane Suilin Lavelle and Kenny Smith
There is a puzzle in the philosophy of mind regarding whether we can know things which we have not had experience of. Although the debate can be traced back as far as Plato's Merio dialogues, it is most commonly connected to the early modern philosophers John Locke (1632-1704) and Gottfried Leibniz (1646-1716). Locke is an example of an empiricist thinker, expounding the view that all our knowledge comes from experience. In his Essay concerning Human Understanding (1690) Locke argued that the human mind starts as a blank slate, and that it is only through experience that it can be 'furnished' with knowledge. This contrasts with nativism, the view that we have some knowledge independently of experience. This was the position advocated by Leibniz in his New Essays concerning Human Understanding (c.1704, first published 1765).
Nowadays philosophers don't advocate extreme nativist or empiricist positions as embodied by Leibniz or Locke. Instead, the argument has shifted to the question 'How much knowledge can we have independently of experience, and what is this knowledge like?' In modern-day science, this question is refrained in terms of knowledge and cognitive abilities. We want to know the extent to which knowledge (e.g. knowledge about plants, animals or other people) is learnt from our parents and peers, and the extent to which it is genetically transmitted to us from our parents. The same goes for certain cognitive capacities, e.g. doing basic mathematical calculations, recognizing our kin or recognizing particular bodily movements as actions.
Two fields in particular have had a significant impact on how philosophers address these questions. The first is developmental psychology: through careful experimentation psychologists can reveal the cognitive capacities of very young infants. The reasoning here is straightforward: the younger the infant, the less experience she has had, and thus fewer opportunities to learn from experience. If an infant demonstrates a particular cognitive capacity before she can possibly have encountered sufficient data to develop it, then, the argument goes, that capacity can't be learned: it must be innate.
The second field to affect the philosophical debate about innate knowledge is evolutionary biology. This will be the focus of the current chapter. Specifically, we'll be looking at how the theory of natural selection affects philosophical accounts of how the mind1 is structured. Our starting premise will be that the human mind is a product of natural selection; how we should understand and interpret that claim will be the source of our debate. We will start by presenting an approach known as evolutionary psychology. This is the hypothesis that the mind evolved as a series of 'mini-computers', each of which is a product of natural selection. These mini-computers evolved to solve specific problems which faced our ancestors, and have barely changed since the Pleistocene era (a period stretching from about 2.4 million years ago to about 10,000 years ago). If one accepts this hypothesis then one is committed to the idea that certain knowledge and cognitive capacities, namely those built into these mini-computers, are innate. Evolutionary psychologists are committed to the view that the majority of our cognitive abilities fall into this category. We will contrast the evolutionary psychology view with an alternative which emphasizes the role of non-genetic mechanisms in shaping human behaviour. In particular, we'll consider the idea that many interesting things people know and skills they have are products of social learning (learning from others), and that these evolve as they are passed from person to person.
Before we can begin to address the question of how the theory of natural selection affects philosophical conceptions of the mind, we first need to be clear about what is meant by natural selection. What we present here is a broad overview of a substantial topic, so do take a look at the further readings to find out more. For our purposes, natural selection is best understood as a process of environmental filtering, where the environment filters out those organisms that are least able to survive and reproduce. In order for an organism or some part of an organism (e.g. a behaviour or physical feature) to be the product of natural selection, three conditions need to be in place:
Condition 1: There must once have been variation regarding a particular feature within a population: some members of the population had it and others did not.
Condition 2: Having the feature yields some reproductive or survival advantage to the organism.
Condition 3: The feature must be heritable. For a feature to persist in a population it needs to be passed from parent to offspring, otherwise there will be no long-term change in the population.
Features of organisms that we think are products of natural selection are known as adaptations. For example, beavers have a split claw on their hind feet that they use to groom their fur, and which is generally thought to be an adaptation. We assume that at some point in the species' history some beavers developed the split claw (variation in the population), and those beavers with the claw were better able to spread oil through their fur, making them more water-resistant than their peers without the split claw. The extra water-resistance meant they could spend more time in the water than the other beavers, avoiding landbound predators and collecting food for the family (the split claw yields survival and reproductive advantages). Having the claw was heritable, so the offspring of these beavers also had it, leading to a long-term change in the population.
While the view that natural selection is a process ol environmental filtering is a useful one, it arguably paints an unduly passive picture of natural selection, with organisms changing to fit the environment they inhabit. But this isn't always the case, as is clearly illustrated with the beavers. Beavers have lots of adaptations to suit the wetland environments they thrive in. But beavers also create wetland environments for themselves: they build dams to block rivers, thus expanding their surrounding wetland environment. Their various adaptations for living in water are selected for in part because they actively change their environment, flooding it, increasing the area that is under water and increasing the advantages that these adaptations provide. As well as increasing these selection pressures, damming reduces other selective pressures: for instance, flooding large areas where they can forage for food minimizes the time they have to spend out of the water, reducing the danger they face from predators. Beavers are a celebrated example of a phenomenon known as niche construction, where organisms change their environment through their own behaviour (Odling-Smee et al. 2003). Beavers are of course not the only animals that do this: you can no doubt think of other spectacular examples like termites building mounds, and, as we will discuss presently, humans. Niche-constructing species adapt to their environment, but they also change their environment, and therefore potentially change the pressures they adapt to.
Niche-constructing animals like beavers also nicely illustrate that animals can inherit more than just their genes from their parents. As well as inheriting, via their genes, various physical and behavioural adaptations, beaver kits also inherit their environment: the dam their parents have built, and the flooded land behind it. This therefore provides a type of non-genetic inheritance, sometimes called ecological inheritance.
Ecological inheritance is rife in humans: think of all the aspects of your environment that your parents and others shaped for you, starting with the hospital you were born in and the house that you grew up in. But as well as inheriting aspects of our environment, we also inherit knowledge and behaviours directly from our parents and others people, not via our genes but via social learning. The ability to learn, to modify your behaviour during your lifespan in response to your own personal interactions with your environment (e.g. through trial-and-error learning), is very common in the natural world. Social learning, learning from the behaviour of others, is also pretty common - other apes and primates do it, but also other mammals do it (e.g. rats), and birds do it, and even fish do it. But humans are undoubtedly the kings of social learning: most of the things you know and the skills you have depend to some extent on learning from others, either via explicit teaching, more informal imitation, or even more subtle social influences on behaviour. Think of all the things you know and skills that you have because you were taught by someone, or that you copied from a friend, or that you read about in a book or saw in a video on YouTube, or that you figured out for yourself just because you were hanging out with your friends in a particular context. On top of ecological inheritance, social learning provides another non-genetic mechanism for the inheritance of knowledge and behaviours, which is potentially crucial to understanding human evolution. We'll return to this idea later in the chapter.
The idea that some of our behaviours and physical features are inherited from our parents via our genes is uncontroversial. It's also uncontroversial that some of these traits are adaptations and have been preserved in our species because they allow us to flourish in particular environments. What is more controversial is how we should apply these ideas to human cognition. We will focus for the next few sections on a view known as evolutionary psychology, which is a specific hypothesis about how natural selection has shaped the brain, before turning to accounts that place much more emphasis on the role of social learning and culture.
Evolutionary psychology is a research programme which promotes a particular way of understanding and exploring the human brain. It is organized around four central claims:
As has already been mentioned, the first of these claims is (relatively) uncontroversial, what is in dispute is how we should develop it. Claims (2)-(4) demonstrate the specific way in which evolutionary psychology develops claim (1). Let's go through them in turn.
If there were to be a catchy slogan for evolutionary psychology it would be that 'our modern skulls house a stone age mind'. This phrase was made popular by Lena Cosmides and John Tooby (1997), commonly acknowledged as the founders of the modern evolutionary psychology movement. They claim that the brains we have now are actually adapted to suit our ancestral environment. This is the environment in which humans as we know them now evolved, and we can place it as being within the Pleistocene Epoch. Evolutionary psychologists refer to the period during which Homo sapiens evolved as the environment of evolutionary adaptation. In the environment of evolutionary adaptation humans lived as hunter-gatherers in small groups. In the past 10,000 years, since the end of the Pleistocene, human societies have changed massively, with agriculture becoming a prominent way of life by about 5,000 years ago, to the human conditions of today where most of us live in large urban populations. But, the evolutionary psychologists observe, those 10,000 years account for only a tiny fraction of the time that hominids have roamed the earth and barely an eye-blink in evolutionary terms. For the previous 1.8 million years our existence depended largely on hunting meat and gathering vegetation to eat, and doing so successfully usually meant having to cooperate with a small number of others. Thus, the human mind evolved during this 1.8 million years to solve the kinds of problems which arose from these living conditions. Although our living conditions have changed significantly in the past 10,000 years, this is not enough time (so the argument goes) for the process of natural selection to have changed the way our minds work; consequently, we have brains that are very good at solving problems which were commonplace during the environment of evolutionary adaptation, but which are not necessarily adept at solving the problems thrown up by living in large, technology-driven urban environments where hunting and gathering are not the primary methods by which food is attained. Hence we have 'stone-age minds' in 'modern skulls'.
What kind of problems did our ancestors face? As hunter-gatherers they needed to distinguish poisonous from nutritious food. They needed to recognize and react quickly to predators like large carnivores and snakes. They needed to find appropriate places to set-up camp, away from environs that harbour diseases and possible predators. They also needed to live and work in small groups, containing kin and some non-kin. This requires being able to foster good social relations through selective cooperation, which in turn requires being able to recognize who is a good person to cooperate with. Reproductive success partially entails cooperating with kin, so you need to be able to recognize them; but it also involves keeping favour with someone who has a lot of power in the group, so you need to recognize the cues which signal dominance and change your behaviour towards those members accordingly. Conversely, you don't want to invest energy cooperating with free-riders (people who benefit from the group without contributing to it) so you need some kind of strategy for recognizing them. These and other problems recurred day after day for over a million years, forming the environmental filter, say the evolutionary psychologists, which shaped the human brain. Certain cognitive abilities, e.g. the ability to detect free-riders, are as much adaptations as the beaver's split claw. Those humans who were able to detect free-riders had a slight edge over those without this ability, and assuming this ability can be biologically transmitted to their offspring (a point we return to presently), the process of natural selection operates in just the same way as it does on the physical and behavioural attributes discussed earlier. The environment in which our ancestors lived, hunting and gathering in small groups, persisted for such a long time that there was ample opportunity for their brains to change in response to the recurrent problems of that environment. The features of the hominid brain, how it works and the behaviours it has generated, evolved during this period to better suit us to our living conditions in the environment of evolutionary adaptation.
The evolutionary psychologist s argument is beginning to come together. Humans faced distinctive recurring problems in the environment of evolutionary adaptation and those humans who survived were those who evolved reliable behaviours to address these problems. Thus the humans who survived were those who had the appropriate neural circuitry to generate the appropriate behavioural responses to the variety of problems facing the average Pleistocene human. These neural circuits persist in today's humans, even though the environmental problems we face are significantly different from those encountered by humans in the environment of evolutionary adaptation. In some cases this can lead to maladaptation. Maladaptations are features of organisms which exist due to the process of natural selection and thus are very well suited to the conditions of a specific stable environment. But if that environment changes and the problems which that feature evolved to respond to no longer exist, then that feature can be detrimental to the organism. For example, the trait of finding salt and fat tasty is beneficial to a Pleistocene hunter-gatherer, as it motivates her to track down calorific sources of food which will give her lots of energy to invest in rearing offspring and gathering more food. But in an environment where sources of salt and fat are rife this craving is a maladaptation, causing humans to consume far too much of these food sources resulting in health problems. The relatively new urban environment throws up survival problems which the brain has not yet had time to evolve responses to, while ancient survival mechanisms persist. Stephen Pinker (1999) puts the point nicely when he observes that we fear snakes more than driving without a seat belt. Although car accidents kill far more people each year than snakes, we have not evolved a visceral response to driving without a seat belt, but 1.8 million years in the environment of evolutionary adaptation was enough time to evolve a response to significant dangers of that time, including snakes.
Advocates of evolutionary psychology claim that the best way to study the brain, to grasp why it causes us to behave in certain ways under particular conditions, requires understanding the environmental problems the brain has evolved to solve. Researchers shouldn't just look at how the brain functions in today's environment because properly understanding the brain means looking at its evolutionary history in a particular way, namely, hypothesizing about the problems faced in the environment of evolutionary adaptation.
The second research commitment the evolutionary psychologists hold is that the brain consists in a series of 'mini-computers', each of which evolved to respond to a particular environmental pressure, i.e. how to detect free-riders, how to recognize when someone's trying to communicate with us (rather than just moving their limbs or vocalizing unintentionally), how to recognize predators, etc.
The position that the bram consists largely in a collection of mini-computers is known as modularity theory, where each mini-computer is referred to as a module. Each mini-computer, or module, evolved to solve a particular environmental problem that faced our ancestors. There is a mini-computer which allows us to recognize faces, a mini-computer that generates a disgust reaction to certain dangerous food, a mini-computer that generates a motivational drive to seek out nutritional food, a mini-computer that allows us to detect free-riders. If one takes this view of the mind, then one sees it as composed of lots of small, specialized units, each devoted to a particular task. To borrow an analogy from Cosmides and 'looby, evolutionary psychology predicts that the brain is like a Swiss Army knife, with lots of tools each specialized to a particular job, but which aren't generally interchangeable. You can contrast this with an alternative view of the brain, which sees it as more like a chef's knife which can be used fairly effectively in a large variety of circumstances, but which isn't specialized to one particular task.
To illustrate this point, it helps to look at one ol the most commonly cited studies that evolutionary psychologists see as evidence for their view. Evolutionary psychologists claim that the ability to detect free-riders is a cognitive adaptation to a problem that recurred throughout the environment of evolutionary adaptation. They argue for this claim as follows. There is a logic puzzle designed by Peter Wason in 1966 which tests whether people can tell if a particular logical rule has been broken (see Figure 5.1). The majority of participants in the first task select the cards with the circle and the chequers. Actually the correct cards to turn are the circle and the spotted card - you need to check that the spotted card does not have a circle on the other side, but it doesn't matter if the chequered card doesn't have a circle on the other side. The rule doesn't state that a chequered card must have a circle on the other side, so it is perfectly compatible with the rule if you turn that card over and find a triangle. However, the vast majority of people who take the test (including students who have taken classes in logic!) get it wrong. By contrast, success on the second test (Figure 5.2), created by Leda Cosmides twenty years after Wason's original problem, is much higher across participants, who find it easier to spot which cards need to be turned over in order to ensure the rule is kept.
Figure 5.1 Logic task (adapted from J. Strangroom, 'The Wason Selection Task', Philosophy Experiments, 2014, www.philosophyexperiments.com/wason/default.aspx (accessed 17 June 2014)).
Figure 5.2 Social task (adapted from J. Strangroom, 'The Wason Selection Task', Philosophy Experiments, 2014, www.philosophyexperiments.com/wason/default.aspx (accessed 17 June 2014)).
Cosmides and Tooby maintain that the best explanation for this is that we have evolved a special mini-computer to detect free-riders in our social environment. This mini-computer starts up when we need to detect if someone has transgressed a social norm, for example, if someone is drinking alcohol they are not entitled to. But because this mini-computer is specialized to the task of detecting when people are violating social norms, it won't be activated by tasks with an identical logical structure but which are not in the social domain, e.g. tasks that require you to detect the violation of a rule governing circles and chequers. The mini-computers can only access the information relevant to their particular job. Survival in the environment of evolutionary adaptation was not affected by the ability to detect the violation of logical rules in abstract (circle-and-chequers) settings, but it seems plausible that it was affected by the ability to detect those who are violating the social standards and expectations of the group. It doesn't matter that the social norms themselves have changed since the environment of evolutionary adaptation: the point is that we can detect the violation of such norms, regardless of what the actual content of those norms might be (e.g. they might be about sharing food, or sanctioning alcohol consumption).
One of the most important arguments for the evolutionary psychologists claim that the mind is a series of mini-computers stems from the argument that complex systems must evolve in a modular fashion. In order for complex systems to evolve it needs to be the case that they can be broken down into less complex parts, each of which evolved semi-independently of the whole. The human eye is a good example of this. First, our very distant evolutionary ancestors evolved a light sensor that could detect daily changes in light and dark. Then retinas evolved cones to detect different light wavelengths, and later rods with greater light sensitivity than cones. Many steps further on, we get to the complex system that is the human eye, with features that have gradually evolved and been added to existing light detection systems. Evolutionary pressures caused individual components of the eye to adapt, but if one component changed it wasn't necessary for all of them to change. If a component that detects colours evolves, this doesn't directly affect the existing systems that detect movement or edges, for example. And one component can be damaged but the whole organ can continue to function. For example, some people's eyes have cones with limited functionality, which affects the range of colours that they can see, but the rest of their vision functions normally.
If the brain is a product of natural selection, say the evolutionary psychologists, then we need to see it as a series of mini-computers, each of which is an adaptation to some particular cognitive problem that challenged our hunter-gatherer ancestors. Each mini-computer has access only to those other mini-computers that produce information relevant to it. In addition, natural selection can act on one mini-computer without having to change all the others. So, our ability to detect free-riders can evolve through natural selection, but this change to the brain's structure doesn't affect the mini-computers that deal with spatial cognition, predator detection, and so on. This is highly advantageous for the overall functioning of the brain, because it means that if one mini-computer breaks down the whole system does not crash. Finally, and crucially for the evolutionary psychology account, the mini-computers of the brain are heritable. They are biologically transmitted from parent to offspring just like behavioural and physical adaptations.
One potential objection to the evolutionary psychology perspective is that it does not fully appreciate how important the environment is in human cognition and development. Let's assume for a moment that there is a mini-computer dedicated to picking out faces from the other visual cues in the environment, and which motivates us to pay attention to those things classified as 'faces'. As the module is heritable we expect each child to have it. But now imagine a sad case where an infant is isolated from birth and has very little contact with faces. Does evolutionary psychology predict that she will still be able to recognize certain shapes as faces when she finally encounters them? Not necessarily. The mini-computer for detecting faces might not get 'switched on' or be able to operate properly if it is in an environment where the appropriate data are scarce. Just because something is heritable does not mean that it will reliably appear in a child regardless of environmental conditions. An analogy might help here: the biological trait of growing milk teeth is heritable and not learned from our parents. But a child in a malnourished environment might not develop milk teeth. This does not mean she has not inherited that biological feature, or that developing milk teeth is not a trait which has evolved through natural selection, but rather that the environment that she is currently in does not allow that trait to manifest itself. The same, argues the evolutionary psychologist, can happen to cognitive modules: they require certain environmental input to be activated. However, the environment isn't necessarily limited to triggering innate knowledge: in the next few sections we'll see how non-genetic 'environmental' routes of transmission can have important consequences for human behaviour and human evolution.
We've already mentioned how humans have a whole set of knowledge and behaviours that are transmitted by social learning rather than the genes: we acquire knowledge and skills by learning them from other people. The catchall term for this socially learned repertoire is culture, which in its technical use just means any system of knowledge or behaviour which is transmitted through teaching, imitation, or other kinds of social learning. Your culture includes the clothes you wear, the technologies you use, the religious beliefs and social customs of your population, and the language you speak.
Other animals have culture too, because they do social learning. The cultures of non-human animals are very simple: they look as if one smart animal comes up with an innovative way of doing something, and this behaviour spreads through the population via social learning. Because of this, each population gradually develops its own idiosyncratic collection of these simple behaviours - their own culture.
The knowledge and behaviours that make up human culture don't work like this: rather than being a collection of simple individual components, the products of human culture are enormously complex. Think of how complex a bicycle is, or a car, or a computer, or even your clothes with all the different fabrics, stitches, buttons, and zips. Or think about how sophisticated the legal and political system is in your country, and how it got to be that way. These complex objects weren't invented by one smart individual. They represent the gradual accumulation of modifications over hundreds and thousands of years. People take an existing object or behaviour, change (and probably improve) its design a bit, then pass on that modified object. This process, where one generation builds on the knowledge they inherit from a previous generation, is called cumulative culture, and it produces enormously intricate, well-designed objects. So at least some of the adaptive behaviours and artefacts that humans possess aren't products of biological evolution - they are the products of cumulative culture.
Cast your mind back to the case of the beavers and their dams. Humans do exactly the same kind of sculpting and shaping of their environment, but on a massive scale. Unlike beavers, the majority of the things we do to shape our environment - wearing clothes, building shelter, growing crops and keeping animals for food, living in large, complex social groups - are not instinctive behaviours, but socially learned: they are part of culture, and you learn how to do these things from the people around you. However, although the way we inherit these behaviours is different (social learning, rather than via the genes), the modifications we humans make to our environment massively change the selective pressure acting on us, in the same way as beavers and their dams. Our ability to insulate ourselves from hostile environments with clothing and housing has allowed us to spread right across the planet, and inhabit environments - like the high plains of the Andes, or the Arctic Circle - which would otherwise be uninhabitable.
As with the beavers, as well as insulating ourselves from selective pressures coming from the environment, our cultural practices have also set up new selective pressures. One of the most famous cases is the evolution of lactase persistence. Most mammals, including the majority of humans, lose the ability to digest lactose, the main carbohydrate in milk, once they are weaned: there's simply no need to carry on producing lactase, the enzyme that the body uses to break down lactose, once you have stopped drinking your mother's milk. But a minority of the world's human population (about 30 per cent of people, mainly located in Northern Europe and North Africa) continue to produce lactase long after weaning, throughout their adult lives, which enables them to drink animal milk and digest the lactose in it.
Why have some humans retained the ability to digest lactose? Lactase persistence is of course a genetic trait, and it's probably an adaptation since it's such a handy ability to have: milk is an excellent food source, rich in protein and fat, and being able to access this food source throughout your life probably has selective advantages. We also know that lactase persistence evolved recently, in the last 10,000 years, as a result of the cultural practice of dairying, keeping animals and drinking their milk. Lactase persistence is common in populations with a long history of dairying, and scarce in areas with no tradition of dairying.
How did lactase persistence evolve? Keeping animals and drinking their milk presumably set up a new selection pressure acting on dairying populations, providing enormous advantages to individuals who were able to digest milk for longer in life. Natural selection kicked in, and the genes of these dairying populations responded to a new selection pressure introduced by the cultural practice of keeping animals and drinking their milk. This biological adaptation probably then fed back into the cultural practice of dairying, allowing more extensive use of dairy products and further strengthening the selection pressure for lactase persistence, in a self-reinforcing spiral of gene-culture co-evolution.
Lactase persistence is probably the most famous example of human genes adapting in response to new selection pressures introduced by human culture, but it's certainly not the only one. Humans are large-scale niche constructors: like many other animals, we alter our environments and the pressures they impose on us, but we do it on a far greater scale than any other species, thanks to our capacity for cumulative culture. Recent estimates using sophisticated techniques to identify the hallmarks of natural selection in human genetic databases suggest that thousands of genes have undergone selection in the last 40,000 years, probably as a result of changes in human lifestyle driven by our capacity for culture. This suggests that the common intuition that the human capacity to insulate ourselves from our environment means that natural selection is effectively over for humans is almost certainly wrong. It also suggests that the classic evolutionary psychology position, that we have stone-age minds in a modern world, probably isn't true. In fact, this research suggests that the rate of human evolution has increased in the last 40,000 years, as we adapt to the new environments our cultures have created for us.
Let's spend a little time applying these ideas to a specific problem, one of the big questions in understanding human evolution and human uniqueness: the evolution of language. Human language is a uniquely powerful and flexible system for communication, which has no parallels in the natural world. Virtually every species can communicate: flowers signal the location of nectar to bees, bees communicate with other bees to tell them about the location of flower patches, male birds sing songs to advertise their availability and quality to females, and many species have alarm-calling systems, where they use specific calls to warn group members of the presence of predators. But these communication systems, fascinating though they are, are all quite rigid and inflexible, and can only be used for the limited, specific purpose they have evolved for. For instance, various species have alarm-calling systems, which they use to warn members of their group of predators. The most famous example of this is probably the vervet monkey. Vervets have distinct alarm calls for their three main predators: leopards, eagles, and pythons. These different predators require different types of evasive action (if there's a python around you want to stand up tall and look at the ground, which would not be a good response to a circling eagle), and vervets know which alarm call corresponds to which predator, and act appropriately. This provides a simple, elegant solution to the problem of communicating information about predators among groups of vervets. But that's all this system can be used for: a vervet can't use these calls to reminisce with its friends about the time they saw that leopard, or to discuss what they should do next time they see a leopard, or ask where they should hang out tomorrow.
In contrast, human language is incredibly flexible: basically, anything I can think, I can communicate to you using language (as long as we speak the same language of course!). Languages achieve this expressive power through a series of clever structural devices. At the most general level, languages have rules: sentences are built according to a shared set of rules, and if you know the rules of a language and the meanings of the words in a sentence then you can work out what someone is saying, even if you've never heard that particular sentence before. Most of the sentences in this book (including this one) are probably completely novel, one-off sentences of English, which have never been written or spoken before and will never be exactly reproduced again, yet you are able to understand them because you know the meaning of the words and the rules for combining words to convey complex meanings.
Within this basic framework, languages provide devices for conveying all kinds of useful information. For instance, you can encode who did what to whom, in order to convey the distinction between events like 'the dog chased the cat' and 'the cat chased the dog'. You can say when an event happened in time, allowing you to convey whether something already happened, or will happen in the future, or is happening right now. You can convey that an event might happen, or will happen, or might not happen, or won't happen, and you can explain why. You can ask questions that require simple yes-no answers, or request more complex information. Different languages might use slightly different structural devices for doing these various jobs, but they all provide a means to do these things, and much more.
How have humans ended up with such a fantastically rich, complex communication system? One possibility is that language, and all these grammatical devices for communicating complex information, is an adaptation. This argument was made forcefully by Steven Pinker and Paul Bloom in a well-known article titled 'Natural Language and Natural Selection' (Pinker and Bloom 1990). They argue that language is a complex biological trait that appears to be designed for communication. The only way to explain such traits is to appeal to natural selection. Humans live in complex social groups. As discussed above, this means we spend a lot of time thinking about social events, like who is cheating on whom. But it also means we rely heavily on communicating knowledge to one another, both immediately relevant information about current social events or survival-relevant situations and the complex set of knowledge, skills, and beliefs that are needed to survive in the world. Language is obviously well-designed for doing all these things, and therefore language must be an adaptation: the complexity and communicative power of language might be a product of an evolved 'language instinct', a mini-computer or series of mini-computers responsible for acquiring, processing, and producing language.
Language clearly involves something that's uniquely human, since no other species has a communication system like language, and attempts to teach language to non-human animals have met with very limited success. But we also know for a fact that languages are socially learned - as mentioned above, they are part of culture. You can see that this is the case in your everyday experience of social and geographical variation in language. People from different parts of the world have different languages, and people from different areas within a language's borders have different accents, because they grew up around people who sound a particular way and learned their language based on hearing those people talk. And those people, in turn, learnt their language in the same way: your parents were influenced linguistically by their parents and peers, who were in turn influenced by their parents and peers, and so on, in a chain of transmission leading back tens of thousands or maybe even hundreds of thousands of years.
We also know that languages change as a result of this transmission process because we can see it happen in the written record: the English of today is very different from the English spoken in Shakespeare's time, and the English spoken 1,000 years ago would be completely incomprehensible to a modern English speaker because the language has changed so much. Our historical record of languages doesn't stretch back very far: writing only emerged and developed in the last 5,000 years, and as far as we can tell the first languages which were written down looked pretty much like modern languages, in terms of having rules and structure. But languages have been around a lot longer than 5,000 years: they must have been around, being passed from person to person by social learning and changing as a result, for as long as our species has existed (and maybe even longer, if you think that earlier hominids had language too). This gives language at least 100,000 years to develop, change, and evolve through the process of cumulative culture described earlier. It could be that much of the complexity and power of language developed over this time. How could this happen?
We know that, in order to survive, languages have to be highly learnable - they have to make it into the minds of language learners. Learners simplify, regularize, and generally tidy up languages as they learn them. Languages therefore evolve over time and develop rules and patterns that learners can identify and exploit, because those rules and patterns make language more learnable. Terry Deacon (1997, p. 110) has a very nice way of summing this up when he says:
The structure of a language is under intense selection because in its reproduction from generation to generation, it must pass through a narrow bottleneck: children's minds. ... Language operations that can be learned quickly and easily by children will tend to get passed on to the next generation more effectively and intact than those that are difficult to learn.
At the same time, we know that people make conscious and unconscious adjustments in the way they use their language in order to convey the kinds of distinctions and messages they want to communicate. You choose the clearest, or funniest, or most inventive, or most colloquial way you can think of to express yourself. People modify their language to convey the kinds of meanings they want to convey, just as they modify their tools and other aspects of culture to improve the way they function - the only difference might be that, with language, these changes are much more subtle, and perhaps less intentional. But spread over hundreds of thousands of years, these changes, combined with the actions of language learners in simplifying and systematizing language as they learn it, could conspire to build complex, expressive but rule-governed languages.
Just like the classic evolutionary psychology perspective on language this is still just a hypothesis, although it has the notable advantage that it draws on processes that we can see operating in the present day and recent history: language learning, language use, and language change. We can test this hypothesis in various ways: while we can't study the very early origins of language directly, we can investigate experimentally how people learn and use language, and we can simulate these same processes in a computer or using real humans in the experimental lab (e.g. Kirby et al. 2008). If this theory is right, then maybe some or all of the features of language that make it so wonderfully useful as a system of communication - rules, word order, case marking, tense, modality, and so on - are a product of culture, rather than a biological adaptation.
Our starting premise was that processes of natural selection have shaped the human brain. From there we presented two different accounts of how this might have happened. The first, evolutionary psychology, says that natural selection shaped a collection of mini-computers, each of which is specialized to solve a particular problem faced by our ancestors in the environment of evolutionary adaptation. Our brains today largely consist in a bundle of mini-computers which are best suited to ancestral environments stretching back up to 2.4 million years ago. The second account suggests that the human brain has evolved significantly in the past 10,000 years. This is as a result of our capacity for cumulative culture which has allowed us to change our environments to be better suited to our needs. Our culturally transmitted niche-constructing behaviours, like dairy farming, have also set up new selective pressures which have driven rapid changes in our genetic make-up. Evolutionary psychology presents a relatively passive view of natural selection, where the organism is constantly reacting to the dangers of its environment. The cultural account, on the other hand, presents the organism as actively altering its environment and shaping the selective pressures acting upon it. This is clearly a caricature of the different views, but it helps to capture the core differences between them.
Humans are unique in the animal kingdom in our capacity for high-fidelity social learning, the sheer amount of social learning we do, and the cumulative culture this produces. Language has clearly played a pivotal role in creating these systems, but again we see a divide between evolutionary psychologists and cultural accounts about how best to explain this. Researchers leaning towards evolutionary psychology will try to find a series of language modules: miniature neural computers that allow us to learn and produce language. Researchers leaning towards a cultural view will look instead at how languages themselves change and evolve, to become easier to learn and more expressive to use.
We've only been able to give a short overview of these positions m this chapter. Research into the interaction between evolution and culture remains ongoing, and provides some of the fiercest and most stimulating debates in contemporary science. The mind may not be a blank slate, but there is a long way to go before we properly understand the nature of the knowledge it contains.
1 Although there is plenty of debate in philosophy and other fields about whether the 'mind' is identical to the 'brain', this is not an issue we will be addressing here. Consequently we will use 'mind' and 'brain' more or less interchangeably.
Cosmides, L. and Tooby, J. (1997) 'Evolutionary psychology: a primer, Center for Evolutionary Psychology, University of California, Santa Barbara [website], www.cep.ucsb.edu/primer.html (Evolutionary psychology, as defended by its original champions.)
Deutscher, G. (2005) The Unfolding of Language, New York: Metropolitan Books. (A wonderfully well-written introduction to how languages change, how they simplify and complexify and what this might mean for language origins.)
Gould, S. J. and Lewontin, R. (1979) 'The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist programme', Proceedings of the Royal Society of London B: Biological Sciences 205: 581-98. (This is one of the most important criticisms of adaptationist thinking in biology, and the arguments can be applied just as well to evolutionary psychology.)
Hurford, J. R. (2014) The Origins of Language: A Slim Guide, Oxford: Oxford University Press. (A short introduction to evolutionary linguistics, from one of the handful of researchers responsible for rejuvenating the scientific study of language origins.)
Laland, K. N. and Brown, G. R. (2011) Sense and Nonsense: Evolutionary Perspectives on Human Behaviour, 2nd edn, Oxford: Oxford University Press. (An authoritative overview of evolutionary explanations of human behaviour, including evolutionary psychology, cultural evolution, and other approaches.)
Pinker, S. (1995) The Language Instinct, London: Penguin. (An entertaining popular-science introduction to linguistics and the nativist position on language.)
Pinker, S. (1999) How the Mind Works, London: Penguin. (An account of how the mind works from an evolutionary psychology perspective.)
Deacon, T. (1997) The Symbolic Species, London: Penguin. (A fascinating and detailed perspective on the co-evolution of language and the human brain.)
Downes, S. and Machery, E. (eds) (2013) Arguing About Hitman Nature; Contemporary Debates, London: Routledge. (This is one of the best collections of papers on how evolutionary theory affects our views of human nature.)
Fitch, W. T. (2010) The Evolution of Language, Cambridge: Cambridge University Press. (A comprehensive overview of the modern scientific approach to understanding language origins and evolution, from one of the leading thinkers and researchers in the field.)
Griffiths, P. and Sterelny, K. (1999) Sex and Death: An Introduction to Philosophy of Biology, Chicago: Chicago University Press. (A clearly written guide to evolutionary theory and its impact on philosophical issues, covering challenging material.)
Kirby, S., Cornish, H. and Smith, K. (2008) 'Cumulative cultural evolution in the laboratory: an experimental approach to the origins of structure in human language', Proceedings of the National Academy of Sciences, USA 105: 10681-6. (An experimental study showing how language evolution can be studied experimentally, in the laboratory with human participants.)
Odling-Smee, F. J., Laland, K. N. and Feldman, M. W (2003) Niche Construction: The Neglected Process in Evolution, Princeton: Princeton University Press. (The definitive text on niche construction.)
Pinker, S. and Bloom, P. (1990) 'Natural language and natural selection', Behavioral and Brain Sciences 13: 707-84. (An influential article setting out the argument that the human capacity for language is a product of natural selection.)
Richerson, P. J. and Boyd, R. (2005) Not by Genes Alone: How Culture Transformed Human Evolution, Chicago: Chicago University Press. (A non-technical but comprehensive discussion of cultural evolution, gene-culture co-evolution, and their role in explaining human behaviour.)
Downes, S. (2008) 'Evolutionary psychology' (first published 2008), in E. N. Zalta (ed.) Stanford Encyclopedia of Philosophy (Fall 2010 edn (archived)) [online encyclopedia], http://plato.stanford.edu/archives/fall2010/entries/evolutionary-psychology/
Odling-Smee, J., Laland, K. N. and Feldman, M. (n.d.) Niche Construction: The Neglected Process in Evolution, Laland Lab, University of St Andrews [website], http://lalandlab.st-andrews.ac.uk/niche/ (An excellent website detailing the theory of niche construction and its relationship to other aspects of biology, including evolution.)
Various contributors (n.d.) A Replicated Typo [blog], www.replicatedtypo.com (An entertaining blog with lots of content on cultural evolution and language evolution.)
Walter, S. (2009) 'Evolutionary psychology', in J. Fieser and B. Dowden (eds) The Internet Encyclopedia of Philosophy [online encyclopedia], www.iep.utm.edu/evol-psy/