Genetics is No Excuse

Daniel S. Levine

September 9, 2001


1959 Sandy Lane
Fort Worth, TX 76112

For the Order of Service (from Erich Fromm, The Art of Loving):

To analyze the nature of love is to discover its general absence today and to criticize the social conditions which are responsible for this absence. To have faith in the possibility of love as a social and not only an exceptional-individual phenomenon is a rational faith based on the insight into the very nature of humans.

Opening Words (from Riane Eisler, The Chalice and the Blade):

Of all life-forms on this planet, only we can plant and harvest fields, compose poetry and music, seek truth and justice, teach a child to read and write -- or even laugh and cry. Because of our unique ability to imagine new realities and realize these through ever more advanced technologies, we are quite literally partners in our own evolution.

Reading (From Richard Lewontin, Steven Rose, and Leon Kamin, Not in Our Genes): Despite its frequent claim to be neutral and objective, science is not and cannot be above "mere" human politics. The complex interaction between the evolution of scientific theory and the evolution of social order means that very often the ways in which scientific research asks its questions of the human and natural worlds it proposes to explain are deeply colored by social, cultural, and political biases.


My career path of developing theories of brain function and behavior arose from a desire to understand disasters like the Vietnam War, and hopefully help to prevent such events in the future. What, I asked myself, made our policy makers do the things they did which harmed so many people and didn't seem to make practical sense? And what made so many average people accept and endorse such policies? "Pragmatic" politics and economics didn't seem to give me complete answers to these questions: it felt like a matter of beliefs and attitudes as well. And ultimately, beliefs and attitudes are influenced by how our brains are organized and how they are affected by, and affect, our experiences.

Yet the brain science of the 1970s when I started out was far from being able to make sense of decisions and beliefs on the levels that really affected people's day-to-day lives and long-term plans. So science has been building bridges toward social problems bit by bit: articles listed on my own web site, for example, show a progression from sensory perception to conditioning to complex cognition to emotional influences on decision making. Now finally in 2001, from a mixture of data from animals, human patients, and brain scans of healthy humans, neuroscience has reached the point that it is starting to have things to say, even if much of it is still speculative, about our basic personality patterns. Science is inching toward answers about whether, and in what circumstances, we are caring or aggressive, loving or hostile, empathic or uninvolved, prosocial or antisocial.

But in order to bring these insights out to the world, science must combat an orthodoxy of its own that is just as dangerous and just as limiting as the orthodoxy of religious fundamentalism. It is the orthodoxy that goes by various familiar names: Social Darwinism; Sociobiology; Selfish Gene Theory. As Riane Eisler put it: selfish genes, original sin, it's all the same thing. And yet Richard Dawkins, the scientist and writer who popularized the selfish gene, once won the Humanist of the Year award!

A best selling popular science book, How the Mind Works by Steven Pinker, gives a good exposition of this orthodox scientific outlook on human nature. Pinker's stance is that essential parts of our makeup vary little if at all across cultures, since they arose as evolutionary adaptations. Unequal social hierarchies of power and concentrations of wealth, so the argument goes, are due to genetic inequalities. Double standards for women and men, both in sexual and in interpersonal behavior, he also says, arose out of the separate evolutionary adaptations of the "selfish genes" of males and females who have different amounts of investment in each offspring. He adds that attempts to transform society, such as the 1960s communes and earlier utopian communities, fly in the face of human nature -- so the best we can do is try to be as humane as possible within these cross-cultural genetic limitations on how caring we can be for each other and the planet.

I believe there are solid scientific arguments against all this. While unequal social hierarchies did indeed arise as evolutionary adaptations, so did cooperative partnerships. Humans as adults, even past reproductive age, must constantly make choices between alternative, and often conflicting, behavior patterns in their evolutionary repertoire. This means that EVOLUTION IS NOT DESTINY!

Such choices would not be possible without the amazing capacity of our brains to be shaped by experience -- which means to CHANGE with experience. How specific experiences influence specific changes in brain chemistry and physiology is barely understood. But in the last decade, increasing evidence has accumulated for long-lasting effects of experience, particularly in childhood, on the human brain. This means not only our families but by our cultures affect our biology!

But what does "changing the brain" consist of? In young children up to the age of about 7, brain changes mean actual growth of new connections, or synapses, between brain cells (neurons), and development of the insulating sheath around neurons which improves the efficiency of electrical transmission. In more advanced areas of the brain, particularly the frontal lobes which are crucial not only to planned behavior but to our moral, social, and empathic senses, these processes of neuron and synapse development continue through adolescence. This result about the frontal lobes suggests that youth programs and other adult and peer influences on growing teenagers really do make a difference in how they develop. UU youth organizers should take heart.

But does that mean our brains are altogether fixed when we become adults, that "an old dog cannot learn new tricks"? No! It is more difficult to learn most things as we get older but still possible -- as indicated most dramatically by Dallas African-American George Dawson, who learned to read at age 98 and co-authored a book about it at age 102.

While adult brains are not growing many if any brand-new synapses, they are strengthening or weakening existing synapses. It was suggested by psychologists as long ago as Sigmund Freud, and found in the laboratory in the 1960s, that some synapses change their biochemical configurations so as to become more effective at transmitting electrical signals if they are repeatedly used. This is believed to be at the basis of most forms of conditioning, such as a connection between "bell" and "food" in one of Pavlov's dogs, or learning, such as a connection between "A" and "B" in a child starting to speak -- however those concepts are coded or represented somewhere in the brain.

Such results suggest that if there is a pattern of stimulation, such as a pattern of caring or abusive treatment of a child, there would be lasting effects on the synapses. And studies of chronically abused children confirm this supposition.

The clinical neuroscientist Bruce Perry and his colleagues from Baylor Medical School showed that responses to persistent abuse can take one of two general forms. One of these is the hyperarousal or fight-or-flight response. This is characterized by increased sensitivity of pathways in the nervous system and other bodily organs (including the heart and endocrine glands) involved in responding to danger. These are pathways that serve a useful purpose, but in this case they become overactive. This means the person becomes more likely to react even to stimuli that are somewhat milder than the initial traumatic event.

The other form of response to abuse is the dissociative response. This is opposite to hyperarousal in that it involves freezing rather than fighting or fleeing. Dissociation is often accompanied by depression or a tendency to withdraw into fantasy or daydreaming, leading in some cases to alcohol or drug addiction.

In the brains of severely abused children, the regions responsible for emotions, including attachment, are 20 to 30 percent smaller than in normal children. In adults who were abused as children, the brain area mainly responsible for short-term memory is smaller than in nonabused adults. Trauma during the vulnerable early years also lead to deficits in attention regulation, self-control, and cognitive ability.

So severe abuse and deprivation have lasting negative effects on the brain. But does favorable early childhood experience have a lasting positive effect on the adult brain?

I believe it does, based on some animal studies show that an enriched environment has positive effects on the brain. The neurophysiologist William Greenough and his colleagues placed rats in what they called an "enriched condition" environment, which provided more stimulation than the environment of typical laboratory rat (though less than the wild environment). The rats reared in enriched cages had more of a certain type of synapse on each neuron in a visual part of their brains than did rats reared in standard laboratory cages. Greenough's group also found that rats who had been taught a complex motor skill had more synapses in a motor area of their brains.

Now we're talking about cognitive and motor skills. But what about caring or aggressive behavior? A lot less is known about that. But we do know enough to say that chronic abuse suppresses the development of biochemical pathways related to positive social bonding, which I now discuss. Conversely, we expect caring interactions to enhance the activity of these bonding pathways.

Fight-or-flight and dissociation are clearly not the only ways we have of responding to stress. Some of us respond to stress by doing, if possible, the same things that give us pleasure when we are not stressed, and some of these involve loving and caring interactions with other people. Shelley Taylor, a social psychologist at UCLA, has described what she calls tend-and-befriend responses to stress, which she says arose as an evolutionary adaptation in female animals and women. Yet the biochemical pathways she relates to tend-and-befriend are actually present, to varying degrees, in both sexes.

Tend-and-befriend specifically depends on a hormone known as oxytocin, which is found only in mammals and was originally identified in relation to maternal functions. But the evidence is accumulating, from both rodents and humans, that this same hormone is actually involved in all forms of bonding and positive social interactions, whether sexual or friendship-related, and in both genders. This is why Sue Carter, a behavioral neuroscientist at the University of Maryland, called oxytocin "the cuddle hormone."

Thomas Insel, James Winslow, and their colleagues at Emory University discovered that oxytocin has broader importance for bonding, in male as well as female animals. Insel and Winslow looked at two species of North American rodents that are closely related but have radically different social organization: the prairie vole, which is monogamous with strong male-female pair bonding and both parents involved in care of young, and the montane vole, which is promiscuous with fathers uninvolved with young. They found that oxytocin attaches to reward-related areas of the brain in the pair-bonding prairie vole but not in the non-bonding montane vole. Also, in female prairie voles, pair bonding -- with the first male they smell after reaching puberty -- can be induced by direct injections of oxytocin, and abolished by drugs that reduce the amount of oxytocin.

The Swedish clinical neuroscientist Kerstin Uvnäs-Moberg found that oxytocin administration in both male and female rats counteracts many typical physiological and behavioral effects of stress. For example, oxytocin causes decreases in blood pressure and in the amount of cortisol, a hormone typically released in stressful situations.

The physiological antistress effects of oxytocin are known to occur in association with both lactation and sexual intercourse. What is less certain, but Uvnäs-Moberg also strongly suspects, is that oxytocin is also released by other forms of pleasurable social contact, such as mutual grooming in animals and supportive friendship in humans.

If oxytocin is indeed involved in a wide range of pleasurable experiences, this points to a physiological mechanism both for the health benefits of positive social experiences and for such therapies as massage. In fact it has been found that oxytocin levels in the blood of women who had never been pregnant increases in response to relaxation massage. Also, in women with insecure personal relationships, the same hormone sometimes decreases with sad emotions.

This same substance, oxytocin, also seems to counteract some effects of addictive drugs. Administration of oxytocin to rats and mice has been found to inhibit the development of drug tolerance, that is, the tendency to progressively need larger doses, to several drugs including cocaine, morphine, heroin, and ethanol, and to reduce symptoms from drug withdrawal.

All these results show that humans, like other mammals, have a genetic basis for caring behaviors. We also have a genetic basis for noncaring behaviors, which may be aggressive, defensive, or both, or else involve withdrawal from others. And both capacities are rooted in evolution.

However, we have much more complex brains than do rodents, largely due to our vastly expanded outer brain layer, our cerebral cortex, with its capacities for complex social learning. So while the fight-or-flight, dissociative, and tend-and-befriend systems are all still present in humans, how much each one is actually expressed, and how much this expression becomes part of each of our personality structure, depends heavily on how many positive or stressful life events we experience.

Through an elaborate network of brain connections, each of us has a different set of associations of other persons and objects with caring or noncaring. Probably most of these associations are learned in the context of family and cultural upbringing. My colleagues and I are working on particular neural connections, between the frontal lobes and deeper brain areas, where we think learning of such emotional valuations take place. But, particularly in humans, conditioning occurs at another level that is equally important. Persistent stress decreases the activity of the oxytocin system itself -- and therefore the ability to bond with anybody. Thus long-term negative experiences have lasting effects on brain chemistry which make future fight-or-flight or dissociative responses more likely and future tend-and-befriend responses less likely.

The long-term effects of positive experience on brain chemistry have been less studied. Yet such preliminary findings as those of Uvnäs-Moberg suggest that persistent positive social bonding or attachment experiences can increase levels of oxytocin and neural "relaxation" pathways this hormone enhances, which tend to counterbalance activities of the stress system that promotes fight-or-flight.

This could help explain why societies, such as the Papago Indians of Arizona, in which parents tend to be lovingly attached to their children and not to use physical punishment, produce caring children. It could also explain how Larry Trapp, Grand Dragon of the Ku Klux Klan in Nebraska, converted to a speaker on brotherhood after a positive encounter with a Jewish couple (see the Sept. 9, 1992, Dallas Morning News). It could explain why positive social bonds are the best predictor of health in elderly people.

It could explain how even mice genetically bred to be violent can become less violent in a supportive social setting. Jean-Louis Gariépy and his colleagues bred mice to be either more and less aggressive and then reared them in isolation, which tends to reinforce aggressive tendencies, up to reaching puberty (about 45 days old). However, if the high-aggression mice were brought out of isolation and placed in groups between 45 and 69 days, many of them became less aggressive and more cooperative.

This experiment shows that genes do not solely determine behavior. It gives a strong argument for the influence of experience on the brain systems mediating aggressive or cooperative behavior. Just bringing the mice into social groups, without deliberately structuring the groups cooperatively, made them more cooperative than their prevalent genes would lead us to expect. Now it's difficult to extrapolate from mice to humans because human social interactions are more complex. Yet this finding of behavioral flexibility in mice suggests at least as much flexibility in humans. This supports the belief that while people may differ genetically in their capacities for caring or altruistic behavior, even those at the low end of the capacity scale can engage in caring behavior if their social contexts are structured in a way to encourage such behavior.

How does the brain decide which of these subsystems (fight-or-flight, dissociation, or social bonding) to activate in what stressful, or happy, or neutral situations? Is there some higher-order control that says, "Now be happy and sociable" or "Now be angry and fight"? We don't know but are working on the answers. The frontal lobes, the areas involved in planning, we also expect to play a part in such high-order control of gross modes of behavior.

In humans, a key area relating to emotion regulation is the orbitomedial prefrontal cortex, a part of the frontal lobes. ("Orbital" means close to the bone over the eye; medial means toward the midline between right and left.) A famous 19th century patient, Phineas Gage, was severely damaged in that part of the brain after a railroad accident in which an iron rod went through his head. As a consequence, Gage lost the ability to make plans and respond appropriately to social situations. This orbitomedial prefrontal cortex, through its connections with other parts of the brain, seems to form and sustain mental linkages between specific sensory events in the environment -- for example, particular people or family or social structures -- and particular positive or negative emotional states.

Through another set of pathways going down to deeper and older areas of the brain, and then into the endocrine glands and to nerves that affect the heart and digestive system, this part of the frontal lobes seems to be able to selectively turn on or off different areas that release different hormones, including the "cuddle hormone" oxytocin and the "fight-or-flight" hormone cortisol. So this part of the frontal lobes seems to regulate the prevalence of large classes of responses such as fight-or-flight, dissociation, and tend-and-befriend. Since the orbitomedial prefrontal cortex seems to store in some fashion the emotional or visceral significance of social memories, the relative strengths of these pathways could be influenced by the amount of stress in the organism's early experiences.

This allows the frontal lobes to play a role in selection between competing responses to both external stimuli and internal states. This area of cortex has evolved in humans to enable us to make these behavioral choices in an increasingly complex social environment. The choices are typically biased toward whatever behaviors, caring or uncaring, are encouraged by the society, family, and other people that a person interacts with.

Riane Eisler in her book Sacred Pleasure argues that throughout history there has been a conflict between those who would inhibit uncaring behavior in order to encourage mutually respectful and caring relations, and those who would inhibit caring behavior in order to protect social hierarchies. When hierarchies are powerful, beliefs, institutions, and behaviors required to maintain hierarchies of control are often seen as normal, including massive economic inequalities, rigid sex role divisions, and environmentally unsound business practices. In our neuroscience framework, such behaviors are viewed not as normal but rather as the pathological results of interactions among large numbers of people whose brains have been disrupted by the chronic stresses inherent in establishing and maintaining hierarchies of domination.

Yet people all through history have overcome whatever genetic tendencies they have to be uncaring. The right of kings to rule and of men to control women and children have been challenged over the last 300 years. The 19th century beliefs in the intellectual superiority of white to darker-skinned races and of men to women have been proved false. Scandinavia and The Netherlands in the last century have developed societies with no huge income gaps, elected officials close to half female, and social policies that promote caring for children, the elderly, and the environment. Finally, archeological data indicate that many prehistoric societies oriented more than current ones toward the partnership model -- societies where we find art idealizing not conquest but nurturing.

So neuroscience and psychology tell us that personality is not all genetic, but an interaction between nature and nurture. Then why do we constantly hear messages that emphasize nature (such as reports about similar personalities in identical twins reared far apart)? One reason is the powerful commercial interests behind genetic engineering.

When genetic aspects of personality are emphasized, people look to genetic engineering to solve many some social problems. If we want to reduce crime, for example, this outlook says we should isolate "criminal genes" and try to reduce their prevalence in future generations. If we want to create future Einsteins, it says we should isolate genes for intellectual creativity and try to increase their prevalence in the next generation. If we want to improve medical care, it says we should look to high-tech modern medicine and genetic research, rather than lifestyle or environment.

The social activist Jeremy Rifkin chronicled the growing biotechnology industry and its efforts to profit from patenting and marketing particular human genes. He noted that this industry depends on scientific theories that favor nature over nurture.

But it's dangerous to base decisions about future generations of people on private profit. Besides, while some genetic treatments are likely to be of benefit in combating diseases that have a known hereditary basis, including such mental diseases as schizophrenia, a focus on genetics alone harms society because it distracts us from thinking about important social influences on personality.

As for criminal behavior, such studies as that of Adrian Raine and his colleagues at the University of Southern California, showing that men diagnosed with antisocial personality disorder have an average of 11 percent less gray matter in their frontal lobes than normal men, have been widely publicized. Yet the lack of gray matter could be due to genes or environment or both. Moreover, another study by the same team, in Denmark where the best adoption records are kept, found that violent crimes were more likely to be committed by young men who had suffered both complications in the birth process and early maternal rejection (an attempt to abort the fetus followed by placing the child in an institution in his first year).

Our goal is applying what knowledge we have to increasing the level of caring and cooperation in the world. With this goal in mind, what are some take-home messages of the studies I report from neuroscience, experimental psychology, and clinical neuropsychology?

The first take-home message is that the question of "nature versus nurture" is not productive, because both genetics and culture are important and they interact. A more fruitful question to ask is "what forms of nurture bring out the most desirable qualities in human nature?" We use "nurture" more broadly than just primary caregiving and the home environment, though those are extremely important. We also include influences on the child's development from schools, religious institutions, the mass media, day care, and youth recreation facilities.

The second take-home message is that caring or noncaring people are not born so much as they are made by circumstances and their own choices. There are people who seem to be innate sociopaths, that is, deficient in brain pathways involved in empathy. Yet at least some violent people are changeable by outside influences, such as the Klansman Larry Trapp mentioned earlier who became a speaker for tolerance (and a Jew!) This dramatic change was brought about by his relationship with a courageous Jewish couple who had responded with caring to his hate messages.

Most of us are genetically capable of either acts of the most heroic empathic caring or acts of the most unfeeling cruelty. Cruelty is related to inappropriate activity of a system in the brain designed to cope with threats to survival. Caring is related to the activity of a system in the brain designed to promote cooperation and social bonding. The amount of stress in the social environment has a great effect on the balance point between these two systems.

The final, and most important, take-home message is that science supports the belief that both formal institutions and informal customs make a difference in human behavior. The enormous effects of positive or negative childhood experience on the adult human brain support the conclusion that a basic investment by society in quality child care, education, and family-friendly employment and vacation policies is not only morally right but economically sound. This means that the "race to the bottom" of social welfare and wages occurring in the early stages of economic globalization needs to be replaced by a world-wide adoption of family and social welfare policies similar to those of much of western Europe. And the supposed genetic limits on human nature provide no excuse for avoiding the hard work of working for progressive social policies.

At the same time, changes that need to take place at the level of societal customs. These involve reclaiming the emphasis of partnership as opposed to domination as the cornerstone of human relations. This means that many uncaring relationships which have been accepted as normal need to be seen instead as aberrations that society should strongly discourage. One example is school bullying, which has received much attention since the 1999 mass shooting at Columbine High School. Others include male oppression of women, overpopulation due to restrictions on contraception, religious glorification of self-induced pain, and cultural glorification of war.

These can be replaced by a valuing of pleasure-based partnership and reciprocity, a positive, spiritual view of sexuality, and cultural glorification of peace. Our brains do not guarantee that we will do so, but provide the capacities for doing so.