Nature & nurtures

Are we victims of our genetics or is the world our oyster? To what extent does the biological nature we are bequeathed at birth determine our lives? 

Many of our major economic, political and social theories include either explicit or implicit assumptions about human nature. For example, are we greedy, selfish, and individualistic or are we generous, caring, altruistic and cooperative? If we are a mix of these things then how do we make a scientific assessment of how such characteristics arise in us, how they exist together, their relative influence, and how they are to be managed?

Society at large is still debating empirical questions like: are we inherently violent; is gender a social construct; are there racial differences that run deeper than skin colour; if our genetics does play a significant role in our behaviour then to what extent are we accountable for our behaviour and how should this be assessed, for example, in a court of law; are there biological circumstances in which punishment is senseless and futile; to what extent can we draw valid conclusions about human behaviour and morality from the behaviour of chimpanzees and bonobos; what is the strength of our various behavioral predispositions and, if we had a scientific answer to this question, then how would this relate to society and its governance, both collectively and individually?

Questions like these have been difficult to answer because our knowledge of how the mind works, and how genetics influences our behaviour, have been imprecise at best, allowing for a wide range of scientifically untested claims to be presented as truths.

This is a topic on which opinion within the academic community has changed dramatically over the last few decades as a consequence of scientific research. In the 1960s many viewed the mind as a blank slate (tabula rasa) on which was written the combined influence of all our experiences, most notable was the psychological school of behaviourism which ignored the mind (too complicated) and simply studied behaviour in isolation. In the social sciences social constructionism ignored any biological considerations in the conduct of society and culture. There was obvious appeal because of the optimistic impression that there are no biological impediments to the resolution of problems concerning gender, race, or class and that socially manifested violence, prejudice, and greed could be managed without looking beyond society with virtually unlimited social progress a possibility. But this was a denial of human nature and the subject of behavioural genetics, which gathered momentum in the 1970s, demonstrated conclusively that it was simply not possible to ignore genetic factors influencing human behaviour.

Science has struggled to unweave the intricate interaction that exists between environment and organism (see Nature & nurture). However, the many assumptions and unfounded claims about human nature are at last being subjected to scientific reason (see Reason & science) through research emerging out of evolutionary psychology, moral psychology (see Moral psychology), behavioural genetics, cognitive science and other disciplines of the mind, many only established only in the last 20 years or so, all working (intentionally or not) to bring ‘human nature’ into focus. The relatively new field of evolutionary psychology has urged us to think of the way our behaviour was moulded in our environment of evolutionary adaptation (EEA). This is most obvious through our predilection for foods that would once have been in high demand but which, when readily available, have given rise to the current obesity epidemic – sugars and fatty foods.

Knowing the (scientific) truth about ourselves is unlikely to unleash a Utopia but it should at least clear away many of the prejudices and misconceptions of the past as we build a better understanding of what exactly we are up against.

The tentacles of the unresolved organism-environment problem reach into (at least) philosophy, biology, genetics, linguistics, cognitive science, religion (humans are inherently sinful) moral psychology, and historical studies of human nature. Commentators prior to the 1960s, no matter how observant or insightful, had little scientific evidence on which to base their conclusions.

This article looks at some of the assertions about human nature (as something fixed) that have clouded or influenced thinking in various academic disciplines and how, within a generation or two, we could see a scientific resolution to this historical lack of scientific knowledge.

The nature vs nurture debate

Studies on human nature often include a kind of biological accounting. What are the sources of all our various biological characteristics? To what extent are our physical features or behaviour derived from ‘inside’ ourselves and to what extent are they imposed from ‘without’. Is a particular kind of behaviour innate (genetically determined) or learned (the result of environmental influences). If this sounds academic and esoteric then it shouldn’t. The answers to these inside/outside, organism/environment, innate/learned questions have major implications for criminology, race relations, eugenics, gender issues, morality, and indeed the whole business of human governance.

The nature vs nurture debate comes to us in many guises and subtle variations. At the individual scale we might characterise the discussion more clearly as the organism/environment debate because this makes the underlying problem more transparent. Collectively it poses questions concerning the relationship between genetic and cultural evolution.

Semantic riddles and logic

First and foremost it should be noted that questions framed in the form nature vs nurture, innate vs learned, nature vs culture imply an either/or relationship. The reader is immediately persuaded that there are two opposing elements that are mutually exclusive when this may not in fact be the case. This way of framing an important problem is undoubtedly a major source of unnecessary confusion but it does not explain all the difficulties that are encountered.

The organism-environment continuum

We tend to think of an organism as a discrete individual: it has a bounding surface and we can inspect all its internal parts seeing how they contribute to the functioning of the integrated whole. We can compare the organism to a watch which exists as a discrete self-sufficient item in the world. However, while a watch exists passively within its environment, an organism is in constant interaction with it because the environment provides its food and its means of reproduction and survival. As a matter of fact this is not a casual or incidental relationship but one of total dependence: an organism cannot exist without its supporting environment. Although, for convenience, we make a distinction between the organism and its environment, in operational terms the two are inseparable. The lesson from natural selection is that the more an organism is aware of and/or responsive to its environment, the more successful it will be.

So, though we speak of ‘the organism and its environment’ and although we need to make scientific assessments of relative genetic and environmental influences, we must always remember that in operational terms the two are inextricably intertwined. This is like the way we need both the length and width of a rectangle to work out its area. Perhaps a more apt analogy would be Einstein’s conflation of ‘space’ and ‘time‘ into a single entity, the ‘space-time’ continuum. Perhaps we should persuade ourselves to think of the ‘organism-environment continuum’ as this is what provides the context for evolution.

Adaptive selection is an emergent biological property that does not occur in physics and for life to persist we need the physical parameters that permit adaptive selection to take place. This means not only factors like energy-harnessing metabolism, a bounded body, and replication but an information flow from the environment into the organism that produces a change in structure or behaviour – a record of the environment in the inner structure. Change the environment and you likely change the organism: the selection criteria of adaptive selection (based on organism-environment interaction) then create order and design.

Physics & biology

The biological discussion of heritability proceeds on the assumption of constraining physics. Biological structure and form are constrained by physical factors of scale as well as genetic factors. There are about 22 orders of magnitude difference between the mass of the smallest insect and largest tree. The largest animals occur in water because here they are weightless while on land gravity has a scaling effect as mass increases. If 1 m³ constitutes 1 unit of mass (1x1x1) then 2m³ has a unit mass of 8 (2x2x2). With increase in size supporting legs and bones must get larger relative to the body. Small size results in increasing speed and agility and great capacity to jump, lift and fly. Falling does not threaten life. Comparing a falling grape and water melon we observe the latter has a smaller relative surface area and greater mass and kinetic energy resulting in shattering when dropped from a height. There is an important scaling law associated with energy use: as animals get bigger they live longer, move slower, have slower heart beat and are generally metabolically slower.

What does ‘innate’ mean?

There is no consensus on what the word innate means since it carries many connotations: as present at birth; a product of the genes; strongly determined and difficult to change; biologically adaptive; typical (universal) within a species.
In the popular imagination it can imply a certain lack of choice or fatalism. The idea of being a product of our genes is incoherent but there is the tendency of innateness to imply a greater or lesser propensity towards certain outcomes – whether something specific like eye colour or general like a form of behaviour. It may be best to abandon such an idea as no trait is determined solely by genes and no trait is unaffected by the environment and misunderstandings seem to be many. Perhaps explanations of what is meant are better than the use of such a word.

Psychology

In the 1960s ethologists emphasised the way behaviour can emerge independently of experience: that a bird raised in isolation still has the characteristic birdsong of its species and so on. There were a host of instinctive behaviours related to mating, nesting, and much more. By the 1990s some researches were claiming that the simple notions of innate vs acquired was oversimplistic and that structures, functions and behaviours that characterise a species are not locked inexorably in the genes but arise in the course of development. A more contemporary view would be that behaviour arises from the complex interaction of contexts, information coded in DNA, internal physiology, and interaction with the environment.

Today more than ever before there is keen academic competition to provide scientific clarity on what exactly influences and controls our behaviour. At one extreme there are those that focus on innate genetic determinants and at the other are those who emphasise the influence of learned or social factors so that we now have a plethora of psychological disciplines arranged along the nature vs nurture dimension, each laying claim to high status in the ‘explanation of human behaviour’ stakes. Behavioural genetics, behavioural psychology, social psychology and so on. Though many of these studies are still in their infancy they are nevertheless providing us with greater insight into human nature.

… at the genes end of the spectrum:

Genetics

If you think that our genetic constitution is vastly overrated then ponder for a moment the fact that you are a human being and not a dog or chicken. Uncontroversially the reason why you are indeed human is a consequence of genetics, even though we may like to add a mild qualifier to this assertion. Scientifically it was only around 1900 with the rediscovery of the work of Gregor Mendel (1822-1884) that it became evident the germ cells contain sufficient information to generate an entire organism through development. Scientific study, notably that of August Weismann (1834-1914) also suggested that information flows from the genome to the organism, not vice-versa.

Universal human traits (evolutionary psychology), individual behavioural differences (behavioural psychology), the subconscious (psychoanalysis and analytic psychology), universal moral traits and reason (moral psychology)

… at the culture end of the spectrum

Culture

Emphasis here is on the cumulative effects of social learning. Social facts that assist environmental adaptation and which are passed from generation to generation and therefore ‘inherited’ like social ‘genes’ have been called memes (Richard Dawkins). The old environmental evolutionary pressures of the natural world that shaped our bodies and minds have now been replaced by human-created artificial environments (niche construction), changing the kind of selective pressures that we are currently exposed to. For example keeping cattle has resulted in the trait of lactase persistence – maintaining into adulthood the ability to digest milk in a process which is called gene-culture co-evolution. Social influences on individual and group thoughts, feelings and behaviours are the domain of social psychology.

Genotype and phenotype

At the most basic level a humans give birth to humans, not cats, and this is a consequence of genetics.

In more direct biological terms a distinction is made between the genotype and the phenotype, the genotype being the inherited instructions (genetic code) of an organism while the phenotype is the actual expression of that organism’s genes – the product of the interaction between the genotype and the environment remembering that most genes are regulators, how and when they are switched on and expressed depends on environmental triggers.^[2]

Scientifically this particular distinction is extremely valuable because it allows us to make some assessment of the relative contribution of genetics and environment in particular outcomes. For example, it may be noticed that a particular species of plant growing at the foot of a mountain grows to about knee-height but at the top of the mountain it seems dwarfed, creeping along the ground. By growing seed of the two plants under similar conditions it is possible to tell whether the dwarf plant habit is due to the plant’s genetic constitution or the different climatic conditions of the two sites.

But we must stay mentally alert about this situation because we now know from the organism-environment continuum that this plant example is useful but it is a short-hand explanation that is not strictly accurate. The phenotypic characteristics of organisms can only lie within the range of what the genotype allows, they are not, as it were, ‘purely’ environmental (arising independently of the organism itself) and this is where our mental picture of what is going on can go awry.

Heritability index

Scientific experiments can be devised to differentiate the relative contribution of phenotype and genotype in the manifestation of particular behavioural traits and these can then be expressed in terms of high to low heritability.

Individual human difference

Twin and adoption studies

Perhaps the most challenging questions of the nature-nurture debate relate to the relative importance of genes and environment in the determination of differences in cognitive ability (intelligence, general performance) and personality (happy, ‘criminal’, cooperative, aggressive). The prevailing belief is that such factors are strongly influenced by parenting, role models, and education. Early studies frequently made assessments based on child-parent correlation without any consideration of genetic relatedness at all.^[6]

Studies in behavioural genetics have addressed these questions through the rigorous analysis of twins, both identical twins (who share all their genes) and fraternal twins (who share half their genes) along with adoptees (who do not share their genes but can share environments) and biological siblings (who share their environment and only half their variable genes). In this way most of the gene-environment combinations can be investigated in detail – specifically, identical twins reared apart (shared genes but not environment) and reared together (both shared genes and shared environment), and in the same way fraternal twins raised together and apart and adopted siblings (who can share their environment but not their genes).(p. 223) The results, listed briefly here, are not what many people expect:

• Identical twins raised apart are highly similar
• Identical twins raised together are more similar than fraternal twins who share their environment but only half their variable genes
• Biological siblings raised together are more similar than adoptive siblings

There are traits that are not heritable at all – like the specific language spoken, religion believed or political party adhered to – while language proficiency, or religious and political; intensity are partly heritable.

Environment (shared & unique) – nurture vs nurture
For humans there are two categories of environmental influence: on the one hand there is the shared environment of parents, home life, and neighbourhood and then there is the unique environment that is experienced by a particular person but not their siblings.

Perhaps one of the most surprising findings of behavioural genetics is that:

• shared environments have little effect on intelligence, personality and behaviour
• Adult siblings are equally correlated whether raised together or apart
• Adoptive siblings are no more similar than two people of the same culture chosen at random
• Identical twins are no more similar than would be anticipated from their shared genes
• Except in extreme circumstances shared siblings home experience in the same culture has little influence on them as adults.

Parents clearly have an effect on specific skills and general happiness but they do not appear to determine their children’s tastes, intellects and personalities in the long run.<sup[7] This suggests an unrealistic belief of many in the strong influence of home life and the value of family psychotherapy, parental micromanagement, even delinquency. There is also the implication that birth order and only child (often considered critical) have few effects outside the home. Child-rearing practices like home-mothering, single or multiple carers, and same-sex carers have little lasting effect.

In fact it has emerged that much of the variance in personality, intelligence and behaviour does not come from either genes or the family environment. One source is possibly the socialization of peer groups. Identical twins in the same home, though very similar, can be readily distinguished, their correlation being 0.5. Peer group does not explain this difference since they are largely the same leading us to ‘sheer chance’. ‘Both popular and scientific explanations of behaviour, accustomed to invoking genes, parents, and society, seldom acknowledge the enormous role that unpredictable factors must play in the development of an individual’.^[8]

The broad findings from studies like these are not widely known. In general terms such studies indicate a strong heritability of traits. For example, it has been found that there is a low heritability index for our specific language, religion, and the political party we prefer, while language proficiency, intensity of religious belief, and how liberal or conservative we are has a higher heritability index.

More than 212 twin studies measuring the heritability of intelligence concluded that 85 percent of identical twins raised together, and 74 percent of identical twins raised apart, had the same IQ compared with much lower percentages for siblings raised together (45 percent) and apart (24 percent) implying that genes are predominant determinants of intelligence.^[3]

One major counterintuitive finding from heritability studies is the influence of family environment on the personality development of children, which is relatively minor (except in cases of severe neglect and abuse). Environmental influences outside the family, such as school and friends, are often more important. However such conclusions always need very careful scrutiny as what constitutes ‘environment’ may have more to do with genes than first appears as people select environments that suit their genetic makeup.^[4]

Of particular interest is the implication from research that identical twins raised under near identical environmental conditions still display difference. It is as though we have three determinants, genes, environment, and chance. The latter cannot be ignored and may be substantial such as twins that are gay or straight, schizophrenic or normal. Obesity studies by Tim Spector of Kings College London hav eshown that in identical twins under some conditions genes can be turned on in one twin but not the other, that is, certain genes can be turned on by life circumstances, epigenetically, such that identical twins display different traits – in this case obesity.

With the advent of genome sequencing, it has been possible to search for and identify specific gene polymorphisms that affect traits such as IQ and personality.

Epidemiology
Our improved knowledge of genetics can inform the way we treat disease.

One day-to-day source of confusion and uncertainty relates to public health and epidemiology. What exactly is the link between smoking and cancer, or cholesterol and cancer – different findings seem to emerge in the news on an almost daily basis in an apparent competition to gain public attention? What are the modifiable causes and effects relating to, say, smoking, drinking, obesity, exercise, and diet? More specifically, what is the scientific basis and authority on which public health authorities can base their recommendations?

Methods of answering such questions are becoming more precise. For example, the ‘Mendelian randomization test’ checks for or assesses a causal effect based on observational data in the presence of complicating factors, and will likely prove more popular as our knowledge of health and disease incorporates findings from genome-wide association studies and genome sequencing. Causes are addressed without taking on the usual biases that plague traditional epidemiological methodology.

The mind

Controversy is especially vigorous concerning the mind and its ‘inside’ and ‘outside’ influences. Knowing that we process all our sensory input within our brains we have all probably wrestled with what exactly we mean by the words ‘subjective’ and ’objective’ in particular circumstances. Though we can appreciate that subjectivity entails a personal perspective on things, perhaps our own particular feelings, beliefs or desires concerning a particular issue, while objectivity refers to something that is true regardless of an individual’s particular situation, something true independent of the mind. But it is not difficult to get confused.

Rationalism & empiricism

The ‘inside-outside’ debate in relation to the mind came to a head when, in the 18th century, philosophers discussing how we gain knowledge and what constitutes the proper technique for verifying what we think we know (epistemology) divided into two schools of thought, the Rationalists and Empiricists. Empiricists claimed that all ideas come to us from experience (a posteriori) (a priori). So in general terms, and at the risk of simplification (there are many subtleties of course), the rationalists maintained that knowledge is gained independently of sense experience, it is simply part of our innate rational nature. Experiences can trigger a process that allows this knowledge to come into our consciousness, but the experiences don’t provide us with the knowledge itself. In this school were philosophers like Plato, Aristotle and Descartes. In contrast the Empiricist position as expressed by philosopher John Locke, for example, viewed the mind as a ‘blank slate’ on which our experiences were written.

It was the philosopher Immanuel Kant who, through his postulation of ‘categories’ (or innate ideas) broke the impasse between these two inside/outside, organism/environment schools of thought. Philosophers might disagree but today this one-time deep philosophical dilemma has become an empirical question with a relatively simple answer. Our minds are not blank slates, they have an innate way of structuring our sense-experience and this determines the way we perceive the world: it is called cognitive mapping.(see Reason & science)

Our thinking still ebbs and flows in our attitude to the degree of inside/outside influences on the brain. At its extreme there is the philosophical position called solipsism, the claim that we can only be sure of the existence of our own mind, we must be unsure of anything outside our own minds because the external world and other minds cannot be known, and therefore might not exist outside the mind. Though this may constitute a rationally coherent position it is not difficult to understand why biological scientists, or any other scientists for that matter, might find it difficult to swallow since their work is based on the assumption of an external world and an acknowledgement of an organism-environment continuum.

Contemporary philosophical concerns of phenomenology and postmodernism focus internally on the ‘prison’ of consciousness, treating our subjective states as some form of ultimate experience, emphasising internal introspection and the individual. There does seem a tendency for today’s philosophy to ignore the fact that we are grounded in what lies outside our minds.(see Reason & science)

How can we affirm the external world? Well, possibly a major (evolutionary) reason why we enjoy sport is because it engages both the body and mind in a vigorous and challenging interplay with objects in the external world: it is a close engagement with space and time just as hunting would once have been.

Behaviour

Until recently it was assumed that to be considered innate a behavioural trait must be both hard-wired and universal or, in other words, it must be unchangeable by experience and found in all cultures.

Since the 1970s our improved understanding of the brain has demonstrated that traits can be innate without being either hard-wired or universal. However, the claim that something is innate or genetically predetermined has been the source of much moral and intellectual controversy.

The interplay between what we are at birth and the impacts of the environment into which we are born are difficult to conceptualise.

To aid our conceptualisation of this relationship between the inner ‘given’ workings of the mind and the various influences that can cause it to change, moral psychologist Jonathan Haidt quotes neuroscientist Gary Marcus who characterises innateness in the mind as follows: ‘it is like a book, the first draft of which is written by the genes during foetal development. No chapters are complete at birth, and some are just rough outlines waiting to be filled in. But not a single chapter-be it the one on sexuality, language, food preferences, or morality-consists of blank pages on which a society can inscribe any conceivable set of words.’^[1] ‘Nature provides a first draft, which experience then revises.’ For Haidt ‘innate’ means ‘organized in advance of experience.’

Evolutionary psychology and moral psychology are currently exploring both the strength of our predispositions for certain kinds of behaviour and the reasons for their existence.

Morality

Morality is deeply concerned with the origins of our moral behaviour. Is it imposed from without as by divine decree, or does it come from within, a product of our evolutionary history, some special moral sense or our moral intuitions? If morality is derived from within us then how is it related to the external world so that our behaviour can be modified in a way that permits us to flourish? Is reason the biological mediator between our inner world and the external world, the mechanism that allows us to self-correct and adapt?

In terms of the inner forces there is always the question of the extent to which morality is an evolutionary phenomenon under genetic control?

Primates

In his book The Bonobo and the Atheist primatologist Frans de Waal argues that human morality, which is generally perceived as being derived from ‘outside’ or ‘above’ as a set of God-given rules, instead comes from ‘within’ us. His thesis is in part a response to the contention that without God there would be no morality (do we really behave morally only from a fear of divine disapproval or retribution?). De Waal points out that moral behavior did not begin and end with religious precepts but is a product of biological evolution. Morality, he says, pre-dates religion and can be seen in the compassion, empathy and other moral behaviour exhibited by primates: this is the biological foundation of secular humanistic ethics. Rather than developing morality from scratch through rational reflection ‘we received a huge push in the rear from our background as social animals’.

The case for there being some biological basis to human morality is compelling. However, though De Waal’s seems optimistic about the idea of morally inherited behaviour this would appear a double-edged sword. Empathy is fine but not everyone would derive comfort from the biological origins of our morality as it would appear to be our biologically-based behaviour that often needs to be be reined in.

Scientifically it is moral psychology that is putting our moral intuitions under the microscope to determine the extent to which our morality is derived from ‘inside’ as innate behaviours, emotions and predispositions that we have acquired from our evolutionary past, and from the ‘outside’ as religious doctrine, social laws, duties, norms and conventions … not to mention the role of reason in all this.

Language

Learning language

The study of linguistics provides a straightforward example of work done in one particular discipline over the last few decades that has resolved a nature-nurture problem. We now know that while individual languages like English and Chinese have clearly been learned in a cultural context (it has been demonstrated that any children capable of learning a language can learn any language with equal facility) it is only the innate structures of the brain that allow language to be learned at all – this innate predisposition to learn spoken languages is obviously not present in other animals, so it is an innate human predisposition. Findings like this are simple to set down in a few sentences but they require hours of painstaking research. As indicated at the head of this article we still have a long way to go but answers can be found through an empirical path when once that path was perceived as inevitably metaphysical.

Language & cognition

To what extent does language control our cognition? Is thought impossible in the absence of language? Do our native languages have a profound influence on the way we think? Most cognitive scientists believe language is simply tool of cognition, playing no major role in thought itself. Do mental rehearsals of behaviour result in images that influence our dual reasoning system?

Sex differences

There is a big difference between, on the one hand, the moral claim that people should not be discriminated against based on sex and, on the other hand, the biological claim that the sexes exhibit both real and substantial physical and psychological biological differences as occurs in other primates. Few jobs require either a penis or a vagina: all the other jobs should be open to both sexes.^[10]

Gaussian bell-curves express variance in characteristics and for many characteristics the male and female curves overlap. So for example for the physical characteristic of human height, at height 5’10” there are 30 men to each woman, and at 6’ there are 2000 men to each woman. Sex differences in cognition are not so marked but they are nevertheless there. Intelligence is similar in both sexes.

Differences:
1. Men are more likely to chase status than family
2. Women desire to work with people rather than things (maths, sciences)
3. Men accept more risk
4. 3-dimensional manipulation is far greater in men
5. Men are better at maths but more variable in ability

Nature and nurture are not involved as alternatives here: they are both involved. Many sex differences are universals. Men are more concerned with aggression and competition, rough and tumble, there are different toy preferences, and cooperation is more a female attribute. Stereotypes do not cause differences. Assumptions about height in jockeys and basket-ball players are based on reality. Tails may be expressed more emphatically in males too – more prodigies and more idiots.

Commentary & sustainability analysis

Nature and nurture are not either/or, they are not alternatives. An analogy might be the way we must think of both length and breadth to make a rectangle with the length and breadth are variables. So innate mechanisms are those that facilitate the operation of nurture – like the circuits needed for learning or language to work at all. Nature is what makes nurture possible. The particular language we speak is entirely a matter of culture while the capacity to acquire language at all is innate. Genetics does not mean that behaviour is fixed but is based on competing behavioural predispositions modified by particular circumstances.

Because of the moral and political implications associated with the debate over nature and nurture it can be tempting to avoid the issue altogether as an inextricable tangle of factors, simply ‘some of each’. However, certain obvious cases challenge this view so, for example, we are clearly genetically predisposed to learn to speak a language but the particular language we speak is a consequence of our culture/environment. Autism and schizophrenia were until relatively recently frequently associated with the home environment and the behaviour of mothers or subjection of children to constant double-binds, a situation that could be treated with some form of family or group therapy. We now know that both conditions are highly heritable.^[9]

We are drawn to the view that behaviour must be genetically determined in a rigid and direct way like eye colour – that there is a violence gene that locks us inexorably into a certain path of behaviour. If this behaviour is geneticaly inevitable then we cannot be held responsible. But political and moral questions are decided on general political and moral principles regardless of genetic make-up. Equality under the law does not mean that everybody must be genetically identical.

A better way of characterising the situation is to regard behaviours as stronger or weaker predispositions or propensities and as such these predispositions can be influenced by many environmental factors like education, the circumstances of the moment, psychotherapy, changes in social attitudes and so on. Though these predispositions can therefore be ‘managed’ that does not mean that we can manipulate the environment to engineer whatever outcome we desire, instead ‘the genes specify what kinds of environmental manipulations will have what kinds of effects and with what costs’(p. 220). So, for example, our predisposition is to sympathise with those close to us in an expanding circle, family, tribe, town, race but by cultivating empathy it is possible to be more expansive in outlook.

The nature vs nurture debate is important because its implications run much deeper than basic biology, in fact penetrating deeply into other disciplines. Each organism has a set of unique genetic traits: that is why human beings have human babies and not kittens. It is the interaction between this gentic foundation and the environment that produces the organism. Nature makes the effects of nurture possible.

Almost any argument about human behaviour can be backed up with the claim ‘after all, it is human nature’. Until recently the scientific basis for judgments abiout human behaviour was very slim and shaky. With little scientific evidence claims could be made either on the one hand that certain behaviour was genetically determined and therefore inevitable or, on the other hand, that the same behaviour was infinitely malleable by social and environmental factors. At long last science is beginning to resolve issues about our human nature that have plagued us since the dawn of time.

Throughout history scholars have made judgements about our human nature without the benefit of empirical evidence. So economists might claim that we are naturally greedy and motivated entirely by self-interest, a religious person might believe that our prevailing human characteristic is that we are born flawed and sinful, others might claim that the human race has a predisposition to be altruistic, automatically showing empathy for our fellow creatures. Because so much history has been the story of warfare perhaps there are grounds to believe that we are inherently violent and that violence is therefore likely to break out at any time.

Up until a few decades ago the scientific orthodxy maintained that almost all human behaviour and our personalities could be explained in terms of (determined by) environmental influences but this view has now been modified as as the field of behavioural genetics^[5] has blossomed and behaviour is more accurately represented as the interaction of genes and environment.

For ease of communication we will probably continue to speak of genetic and environmental influences since each can clearly be weighted in relation to the other but we must remember that that totally isolating genes (nature) from environment (nurture) mistakenly ignores the fact that there is always an inseparable interplay between the two and of course this is always a matter of degree.

In an important sense we can regard culture as an extension to biological adaptation since it is a potentially adaptive immediate response to changing and unpredictable environments.

Science is now unravelling exactly what it is we mean by ‘human nature’ and this has a major bearing on how we will manage planet earth in the future. This article might shed a little light on how this problem plays out in different ways while acknowledging that there are few simple answers. The path from gene to behaviour is complex. Natural predispositions can be expressed to a greater or lesser extent in different individuals and to a greater or lesser extent at different times, and they can be variously affected by social factors.

Key points

• The problem of nature and nurture draws attention to our tendency to make unfounded assumptions about human nature. Such assumptions have become embedded not only in biology but also literature, economics, philosophy and other disciplines

• The consequences of our conclusions about nature and nurture have implications for criminology, race relations, eugenics, gender issues, morality and much more

• An organism is both intricately intertwined with and ultimately totally dependant on its environment so to causally separate the two is at best confusing. It helps to acknowledge this fact by trying to ignore their separation and thinking of the ‘organism-environment continuum’