On The Nature Vs. Nurture Debate:
Do Genes Or Environment Determine Human Behaviour?

- Aparthib Zaman

The question that has always intrigued philosophers and thinkers is whether human behaviour is determined by nurture, i.e through the effect of environment, learning, upbringing, (in one word cultural conditioning), or by human nature, i.e by inborn genetic traits that are inherited at birth. The two extreme positions on this question are environmental or cultural determinism and genetic determinism. In past, in the absence of scientific knowledge and evidence people took one position or the other based on their gut instincts and perceptions and were often based on a bias that suited their political or ideological leanings. Thanks to advances in genetics, neuropsychology and evolutionary biology, we now know that both factors play a role, although the genetic factors are more fundamental than cultural one in shaping human behaviour. A popular answer to the question: which is important, nature or nurture is by asking the rhetorical question, which is more important in determining the area of a rectangle, its width or lenght? (Implying both are). It is true that both are important, but unlike the rectangle's length and width, nature and nurture do not bear such a symmetrical importance in the determination of human behaviour. Later discussion will clarify this further. Although vey few today are strictly genetic determinists, there are still quite a few strict cultural determinists, because such a biased view suits their political or ideological stands. A strict environmental determinism is deemed a politically correct stand, regardless of what scientific evidence indicates. By assuming a blank slate hypothesis (Tabula Rasa) first theorized by philosopher Locke, a sense of egalitarianism is aimed at. That explains for example why Marx taught that many human characteristics were caused by environmental factors, which are now known to be inherited through genetics. In Soviet Union Stalin tried to twist genmetics to comform to Marxist dogma and denied genetic inheritance. A charlatan scientist named T.D Lysenko was appoinetd by Stalin for this purpose. When genuine scientists like Vavilov pointed out the scientific flaws of Lysenko's theory, they were sent to the gulag by Stalin. Teaching of genetics was banned by Stalin because it contradicted Communist dogma. See http://www.cyberussr.com/rus/lysenko.html and http://www.secweb.org/asset.asp?AssetID=238 for more on Lysenko. Scientific evidence does not support a blanket nurturist view, the blank slate hypothesis. Even a careful thinking can expose the inconsistency of a blank slate hypothesis. If all humans are born with a blank slate, then how can a mind(brain) learn at all? A blank slate cannot write on itself or on another blank slate!. The nature nurture issue is a prime example where scientific insight and evidences are ignored in favour of a biased politically correct answer to this essentially scientific question. I will dwell on the scientific and logical answer to this question. Most of my discussionis based on the insight gained from evolutionary psychology by reading various books by psychologists, biologists, neuroscientists, and science journalists. I will quote from some of the books, not all. We can represent the effect of environment and gene through a visual aid as shown below diagrammatically.

                ...
              ........
         .......****......
       .....*************.....
    .....******************......
   .....*********************.....
  .....***********************.....
 ......***********************......----- outer Shell (".")
 ......***********************......	  (represents Epigenetic Effect
  .....***********************.....                     of environment)
   .....****************------------ Inner core ("*")
     .....******************.....	  (represents genetic factor)
      ......*************......
         .......****.....
              ........
                ...

In the above diagrams the outer shell region (marked by ".") indicates effect of environment, learning, upbringing etc (nurture). The central core (marked by "*") indicates the genetic influence (nature). I refer to mind and brain in an interchangeable sense consistent with the views of contempoorary science, which says that mind is a sort of program running on the brain as the hardware, the programmer being the blind laws of evolution.

In biological parlance the inner core represents the genetic propensities coded by the rules of epigenesis (i.e the rules of how the basic architecture of an individual mind/brain is formed), which in turn is determined by genes. So the basic architecture of human brain (i.e the synaptic connections) is formed early on in infancy by the rules of epigenesis, which is represented by the core. The shell represents the effects of environment, i.e culture and learning, which causes additional neuronal wiring in the neocortex area of the brain througout one's lifetime. Although the shell (Which are the synaptic connections of neocortex by neuronal firings triggered by environmental stimulus) is formed by environment, the nature of the shell is in turn determined by the core, i.e the epigenetic rules themselves. In other words although environments do shape a human behaviour to some degree, it does not shape it identically for everyone. Because similar environmental stimulus will evoke different behavorial response in different human (due to different epigenetic rules). In other words, even though it is true that many traits are shaped by environment, how a given environment shapes a given trait is determined by genetic factors. To quote Steven Pinker from page 102 of his "The Blank Slate: The Modern Denial of uman Nature":

"Neuroscience is showing that the brain's basic architecture develops under genetic control. Brain systems show signs of innate specialization and cannot arbitrarily substitute for one another"

A nice metaphor to illustrate this fact is a computer program whose output is determined by both the input and the program structure(code). The same program code can produce different outputs for different inputs, or two different programs can produce different output for the same input data. Both the program structure and input data together determine the output result. Thats why even under identical environment two humans would still have different moral values. It is also very important to take note of the fact that certain traits are entirely genetic and not shaped by environment. In the computer metaphor, this is equivalent to saying that certain outputs of the program are generated solely by the code without needing any input, and are not changed by whatever input is fed to it. Studies of idetntical twins corroborate the effect of gene in many traits. For example Steven Pinker mentions on p-20 of his book "How the Mind Works" that Identical twins study corroborate gene's strong influence on traits. He also mentions on page-47 of his book "The Blank Slate" that Identical twins have similar views on death penalty, religion (and controversial values), their EEG crags and valleys are alike. and that virtual twins, two unrelated siblings brought up in identical environments, are like night and day.

Pinker also points out that twinning and adoption are natural experiments that offer strong indirect evidence that differences in mind is due to differences in the genes.

So to summarize, some humnan traits are determined by genes, others by a combination of gene and environment. Traits are seldom determined solely by environment, although it is possible that certain behaviours can be solely determined by environment. Traits are natural expressions of genetic propensities. Propensities are always prescribed by genes. As sociobiologist and Pullitzer wining author Edward O. Wilson says on page-89 of his book "In Search of Nature":

"What the genes prescribe is not necessarily a particular behaviour but the capacity to develop certain behaviours and more than that, the tendency to devlop them in various specified environments"

Propensities are reflected in thoughts and feelings that act find expression through natural and spontaneous behaviours called traits. But certain behaviours (i.e actions) can be forced by environments to be counter to one's natural genetic propensity.

According to lessons from contemporary sociobiology the following sequence describes the relationship between nature (gene) and nurture(culture) : gene(prescribes) the epigenetic rules, i.e the rules of how the basic framework of an individual mind is formed, and the individual mind in turn grows further through cultural influence (neuronal wiring), and in turn shapes culture. So its tightly coupled relationship and is called gene-culture co-evolution.

There is an internal inconsistency in the nurturists' assertions like "human are not born evil. They are made evil by bad environment". The implication is that environemnt is some autonomous being external to human mind. But the fact is that environment made up of humans, or is product of humans(brains). For environment to be bad, the humans who make up that environment have to be bad in the first place. Its not a chicken and egg problem. Human nature itself gives rise to environment. In a sense an environment is the totality of all human brains that exerts influence on an individual brain that they surround, in a certain community of people. So enviroment is ultimately a product of the gene pool of that community.

Again to quote sociobiologist E.O. Wilson from the chapter titled "Culture as a Biological Product" in his "In Search of Nature":

"Culture is ultimately a biological product" (p-107)

"To summarize this point, culture is created and shaped by biological processes while the biological processes are simultaneously altered in response to cultural change." and "Culture is rooted in Biology. Its evolution is channelled by the epigenetic rules of mental development, which in turn are genetically prescribed." (p-110)

"Culture is deeply rooted in biology. Its evolution is channeled by the epigenetic rules of mental development, which in turn are genetically prescribed. We can envisage the full chain of causation from genetic prescription to the formation of culture and back again through natural selection to chnges in gene frequencies" (p-126)

Wilson also points out that even the epigenetic factor is prescribed by the gene and thus different individuals posses different epigenetic rules, i.e although environment does play a role in the development of an individual human(mind), the effect is different for different individuals under identical environment, culture etc. In other words genetic propensities are modulated by the environment. For example "Sex on the Brain" , author Deborah Blum says that "Gene determines the baseline testosterone in male and females. Environment adds the fluctuation around the baseline".

When we say that a certain behaviour of an individual is due to environment, not due to his gene, the true significance of this statement is hidden behind semantics and is not realized by even those who make such statements. What it means is that the behaviour in question is not caused directly by HIS/HER individual gene, or a complex of genes.

We have to distinguish between proximate vs. ultimate cause of actions and behaviour. A gene can be a proximate cause of behaviour when the behaviour is a direct result of a gene or complex of genes in the DNA of that particular human. But a gene can also be an ultimate cause of behaviour when the behaviour is shaped through the cumulative effect of gene- culture coevolution happenning within the gene pool from past upto the present when the behaviour in question has occurred. Put simply, when we say the gene is responsible for a behaviour, what is meant is that it is only the gene of the individuals' DNA in action that is causing that behaviour. When we say that environemnt is causing the behaviour, what is meant is that it is the aggregate genes of the gene pool of the community, coevolving with the culture over an evolutionary time scale to produce that specific environment/culture which causes that behaviour. Gene is still at the bottom in both cases, only the mechanism is direct in one case, and indirect(evolutionary) in the other. Again it may be relevant to quote Steven Pinker form page 69 of "The Blank Slate": "History and culture can be grounded in psychology, which can be grounded in computation, neuroscience, genetics and evolution." All organs of human (or any animal) are shaped by evolution. Brain, as the most complex organ, certainly evolves too. And since behaviour is linked with brain, human behaviour is ultimately governed by evolution. And evolution in turn is determined by the biological imperative of the maximal replication of genes via mutation and natural selection. So there is a gradual hierarchical layers of causation from higher to lower levels.

There are other obvious flaws in the nurturists' insistence that human values and behaviours are learned and taught, not inborn. This is not strictly true. Many traits, behaviours are due to inherent propensities. For example, as Steven Pinker says on page 44 of "The Blank Slate" that "Intelligence, scientific genius, sexual orientation and impulsive violence are not entirely learned." And on page 51 Pinker says that "Genetics and neuroscience are showing that a heart of darkness cannot always be blamed on parents or society." If learning could influence or shape human behaviour or traits then psychopaths could be cured. But they cannot be, as Pinker says on page 263 (op cit) "Psychopaths cannot be cured" And on p-315 Pinker reiterates that "There is little doubt that some individuals are constitutionally more prone to violence than others". Another classic case provng that dark sides of human behaviour is not really learned or culturally shaped is that of Jack Abbott. Pullitzer author Norman Mailer freed a prisoner Jack Abbott from the jail being impressed by his letters written by Abbott to him, which were published by Mailer as a book in 1980 titled "In the belly of the beast", fetching a Pullitzer award for him. Abbott was treated as a celebrity and feted at literary dinners. Two weeks later, he stabbed a waiter in a restaurant on an argument on not using the employees restroom! (cited in Pinker - Blank Slate, p-262).

Many cultural determinists argue that sexual abuse by many are due to the abusers themselves being victims of sexual abuse in their childhood. This is not true necessarily. Joan Allen Rodgers in her book "Sex: A Natural History" says that there is evidence that many who sexually abuse children have no history whatsover of abuse in their own lives. And on p-429 she quotes geneticist Fred Berlin and says that deviant sexual behaviour (sexual paraphilia) also cannot be taught, but is rooted biologically, but hastens to add that society must punish such acts to protect victims, but should not preclude study and understanding of such behaviours. Steven Pinker on page 311 of his "The Blank Slate" cites the fact that Canadians watch the same television shows as Americans but have 1/4 the homicide rate as US, debunking the allegation that violent TV shows teach violent behaviours.

Pinker also questions the common belief that children learn violence while growing up by external stimulus. On page 316 he mentions that "children are violent well before they have been infected by war or toys or cultural stereotypes. The most violent age is not adoloscence, but toddlerhood." He also quotes from C. Holden in "The violence of the lambs", Science, 289, 2000, pp-580-1 :

"Babies do not kill because we do not give them knives and guns. The question we have been asking, how do children learn to aggress? But we should ask how do they learn not to agress."

We see many examples that further contradict the myth that human mind and behaviour is formed through learning. We see people becoming religious when not subject to religious teaching or brainwashing, and people become atheists despite heavy religious indoctrinations. One exception should break a rule. If values and mental inclinations were leraned and taught, the such exceptions could not occur.

One of the bitterest lesson of parenthood is that children don' t always turn out the way their parents want. It shows again that not anything that is taught will be learned. People will learn more easily if what is taught is favoured by their genetic propensity. Some parents may teach something that is not in their genetic propensity, for example a parent may, for practical reasons try to teach medicine or engineering to his child although his own or his child's genetic propensirty is for arts. That is not guaranteed to succeed.

Now let me come back to the reasons for holding a strictly cutural determinstic (i.e blank slate) view. One reason that many who reject "nature" do so because an nature view has two uneasy implications. For one thing they are afraid that then any act can be justified as being genetically programmed and hence beyond one's control, and thus would preclude any accountability for a wrong act. This logic can cut the other way too. If an action or behaviour is deemed as strictly environmentally determined then also it is beyond one's control and can equally deserve to be exempt from accountability. Adopting cultural determisnism does not provide any adavantage ovber genetic determinism as far as accountability is concerned.

Secondly it is feared that admitting genetic determinism can justify human inequality due to genetic superiority in talents and other traits of one human over another and seems to go against the notion of egalitarianism, which was the motivation for rejecting genetics by Marx, which was discussed earlier in this essay. But these are all misdirected concerns. Human equality should not be based on identity of genetic traits and qualities. Any system or ideology, whether it is communism or whatever, should be judged on its own merit for its acceptance or rejection, it is dangerous to justify or base any ideology on an assumption that is unproven, or is contrary to scientific evidence. Equality (in rights) is an important universally acknowledged humanistic ideal that should not be contingent on any other assumption. As biologists Earnst Mayor says in his book "Animal species and evolution" that equality should not be based on claims of identity, since if latter is disproved, the former is lost. (quoted on p-146 of "The Blank Slate - Pinker). This is true for gender, racial or other equality (in rights) as well. The saying "All human are born equal" should really be phrased as "All human are born equal in their rights". They need not be born equal in traits and qualities like talents, moral judgements etc. Equality between every human in their genetic potentials (whatever criteria is used to measure them) is a biased opinion that is not based on scientific or logical grounds.

Also the fact that some act or behaviour is explained as genetically programmed does not (and should not) necessarily translate into a "sanction" of that act. Explaining is not exculpating.

As Wilson warns on p-93 of "In Search of Nature" against naturalistic fallacy, i.e the fallacy of assuming what is, should be. The "what is" in human nature is to a large extent heritage of a Pleistocene hunter gatherer existence. Wilson points out that the demonstration of a genetic bias cannot be used to justify a continuing practice in present and future societies.

I quoted Fred Berlin earlier who also emphasized punishment as deterrent to protect victims from sexual deviants, but also emphasized understanding of such deviant behaviour.

Genes in our body issue orders, so to speak, but we can disobey their orders. Many of these orders served their purpose in our evolutionary past and exists in us as a vestigial reminder of that time. Much of it may not or does not have much value in the present time, excpet for some basic biological imperatives. A punitive or preventive act in response to a wrong act by another is also in our nature as one such imperative and acts as social deterrents against such acts. It is as much a part of the collective human instinct as is the instinct to commit wrong by individuals. This provides the necessary checks and balance for natural selection process to maintain an evolutionary stable equilibrium in a species and helps it to survive and propagate. So just because one understands that an intruder is acting on his genetic impulse does not mean one will sit back and welcome the intruder. He would fight back to drive the intruder away and protect his property. This is a defensive biological imperative of human ( or any animal for that matter) and cannot be overrridden by any biological insight into human impulses. Now lets look at the other side of the coin. If altruism is also explained as a natural instinct, not cultivated or learned, does it mean that we should not appreciate altruism as a human virtue anymore? After all, what we call altruism, is known from the insights of sociobiology as nothing but a mechanism for selfish genes to maximize their replication through what is known as kin selection. Whether to appreciate altruism, is a judgement call. There is no "should" here. It is just that appreciating altruism is also in our nature. Because not all humans adopt altruism as the means of selfish replication of the genes. The cynical assertion: "There is no true altruism. An altruist is also driven by selfish desire to get gratification through altruist acts" is a hollow assertion since the gratification comes only AFTER the act of altruism as an effect. An effect cannot be the cause of an action. It is true that one knows beforehand that the gratification will follow an altruitsic act but that is only in hindsight from a previous experience of altruism and is used as foresight therafter. So the root cause of altruism is not the desire for gratification. The root is in the genetic makeup. So although altruism is rooted in one's nature(genes), and not due to one's conscious choice (conscious choice does not exist in isolation from the genes, rather it is a manifestation of the underlying genetic makeup along with the interaction of that genetic makeup with environment), its nevertheless something to be appreciated and valued. After all, not all selfish acts benefit others. Altruism, if it is a selfish act at all, is one which benefit others. The real insight comes from recognizing that altruism has an evolutionary value in terms of gene propagation. We humans instinctively value traits that are evolutionarily advantageous.

The second reason many reject nature because that seems to legitimize an uneven playing field and attribute the misery and failure of one segment of society (A) to their own inherent limitations as well as attribute success and happiness of the other segment(B) to their inherent natural advantages. A naturist stand prevents "A" from falsely blaming B for A's misfortune. On the other hand by insisting on nurture it relieves A of accepting any responsibility for their misfortune and makes it easier for them to blame society (B) making them scapegoat for not providing the proper nurturing and causing their misfortune. But this can cut both ways. If a nurturist position is adopted, then in a zero discrimination society, the poor will be blamed for their fate by choosing not to utilize the potential, whereas if innate differences are acknowledged, then in a zero discrimination society, poors cannot be blamed for not utilizing their potential to the full. Of course, nature or nurture, zero discrimintaion society is a must. It is a humanistic imperative that follows from the equality (of rights) of all humans. Whether to enforce an equality of properties and priviledges between humans in an equal rights (zero discrimination) society, where unequal properties and priviledges can arise due to innate differences of human abilities and potentials, is a political and social judgement, it is not mandated or forbidden by scientific evidence.