What makes you who you are? This question is the essence behind the nature versus nurture debate. It is also a question that has plagued scientists for centuries, and philosophers before that. Recently, the debate has raged over which of two major factors has the biggest impact on one’s development. With advancements in genetics, such as the mapping of the human genome, scientists have a better understanding of what traits are inherited. Obviously, certain physical characteristics, such as hair, eye, and skin color, are defined by genes passed on from one’s parents.
However, the line is not so clear when it comes to psychological conditions, behavior, and intelligence. The environment in which a child is raised also includes a number of influences, such as their parents (or lack thereof), relatives, socioeconomic status, and resources. The debate had centered on how much of those characteristics are determined by genetics or from one’s environment. Advances in modern science suggest neither nature nor nurture is exclusively responsible in favor of an interactive relationship between our genes and environmental influences.
While this proposed compromise would be immensely complex, where one helps to shape the other in ways scientists have yet to completely understand, it would essentially end the debate once and for all. The term “nature versus nurture” was coined by Sir Francis Galton in 1871, but the debate actually dates back to ancient Greek literature and philosophers who questioned the nature of fate versus free will (Lewis). Galton referred to the phrase as a “convenient jingle of words, for it separates under two distinct heads the innumerable elements of which personality is composed” (M. S. , M. B. ).
The mindset of this phrasing stuck with the debate, carrying the notion of two separate and opposing scientific views, and extending his influence long after his controversial work had been published. Many of the theories Galton developed were heavily influenced by his cousin, Charles Darwin, whose works on evolution and natural selection were controversial in their own right. At the time, the most commonly held idea was that “a child was born into the world a blank slate, a ‘tabula rasa’ in the words of British Empiricist David Hume” (Lewis).
This belief, also known as environmentalism, is synonymous with what became the nurture side of the debate. Galton’s Hereditary Genius became a source of controversy by resisting this notion and claiming that biodeterminism was responsible for the most eminent, or intelligent, men of his day. By applying Darwin’s theory of natural selection to human intelligence, Galton’s ideas gave birth to the debate as well as a number of other brands of science, such as genetics, psychology, and eugenics. With the scientific developments in genetics over the past century, the debate is cast in a much different light today.
Although Galton and Darwin’s ideas were highly controversial and not well-received immediately, they grew in popularity towards the second half of the 19th century. Scientific understanding of genetics and inheritable traits grew over the next century with Abbot Gregor Mendel’s work establishing the principles of genetics (Lewis). Scientific development during this time laid the ground work for processes, such as genetic recombination and genetic mapping, which have become increasingly important in recent decades.
The Human Genome Project was completed in 2003 by an international team of scientists, but there is still much to learn in the field of genetics. Scientists continue to study how genes interact with each other and influences from external stimuli and conditions. One such emerging, yet controversial, field in modern genetics is eugenics, or the ability to engineer a baby’s DNA to promote or suppress certain traits or inherited conditions. By the 1920’s, Galton’s ideas about eugenics had begun to gain considerable ground both here in the United States and in Europe.
His claim about the inheritance of intelligence among the eminent men of society naturally led to plans to consolidate this genetic advantage in order to improve the human gene pool, falsely giving racism and discrimination some scientific backing. The culturally biased IQ testing of immigrants began to become more frequent. Essentially, the field could be divided into positive eugenics, which seeks to promote good genes, and negative eugenics, aiming to suppress less desirable genes.
There were several horrific applications of negative eugenics during the early 20th century, most notably the Holocaust, in which Nazi Germany sought to eliminate the entire Jewish people and pursue their version of a pure race. Today, negative eugenics has fallen out of favor, but genetic screening and engineering has given positive eugenics a new and growing application. In addition to the advent of genetics, psychology developed in order to study the behavioral and personality impacts from both genes and the environment.
Perhaps the most controversial of Galton’s claims was that intelligence was an inheritable trait, and thus passed down from the elite of society. He conducted a number of surveys and studies to better understand human intellect and also coined the term “mental test” (Lewis). This belief about intelligence, while not as prominent, still exists today in underlying notions about immigration policy and social discrimination. There are many who attribute up to 80 percent of an individual’s I. Q. o genetics, leading some to believe certain racial stereotypes about intelligence, while others attribute those trends to social inequalities (Glass). Today, scientists have made a great deal of progress in understanding how certain mental disorders and personality traits can be transmitted genetically or through environmental stimuli. However, there is still a great deal to learn about the causes of psychological disorders and conditions, including how to prevent them and whether nature or nurture is responsible.
While developing from these relatively new scientific fields, the nature side of the debate has been promoted by those who believe heredity is ultimately responsible for an individual’s characteristics. Modern science has identified a number of physical characteristics which can be definitively tied to specific genetic phenotypes, or genetically-controlled trait, such as blood type and eye color. Those who adopt an extreme heredity position, or nativists, basically assume “that the characteristics of the human species as a whole are a product of evolution and those individual differences are due to each person’s unique genetic code” (McLeod).
They believe that behavioral tendencies and personality traits that even emerge or mature later in life are merely the result of genetic expression tuned to a sort of biological clock, much like puberty in adolescents. This belief supports the notion that certain people are born not only susceptible to hereditary diseases but also behavioral or psychological conditions, such as alcoholism or violent tendencies. While this stance is controversial for many scientists and psychologists, it lends support for positive eugenics’ pursuit of identifying and eliminating these negative traits by genetic engineering means.
In many ways, this view is the modern extension of ancient philosophers’ thinking about free will. It brings up a number of difficult questions about genetic fate with few or no clear answers. For example, how many of our everyday decisions are made of our own free will or just an expression of our innate genetic tendencies is a murky subject. Additionally, whether or not it is possible to overcome these influences is another gray area. If genes are solely responsible, then there exists a sort of genetic predetermination, in that who we become has already been determined before we exit the womb.
Conversely, if the environment is solely responsible, then everyone starts essentially as the same blank slate and our unique experiences then make us who we are. At this other end of the spectrum is the nurture side, who believe that we are shaped by a number of environmental factors. Proponents of this approach are the environmentalists or empiricists “[whose] basic assumption is that at birth the human mind is a tabula rasa and that this is gradually ‘filled’ as a result of experience (e. g. behaviorism)” (McLeod). A person’s personality and any behavioral conditions are then acquired or learned from their surroundings.
Perhaps the most important environmental factor in terms of influence on a child’s development is parenting. Many levels of infant development come from imitation of and response to its parent or guardian. For example, an infant forms an attachment in response to the love and attention it receives from its mother. Later on in life, broader cultural and social stimuli help shape children according to the norms of the society in which the child was reared. To learn more about the extent of these stimuli versus genetic influences, scientists have turned to a variety of studies and experiments.
In order to learn more about the extent of genetic and environmental influences on one’s psyche, geneticists and psychologists alike have searched for a means to isolate one from the other. Identical twins provide a unique opportunity to study the effects of environment on a child’s development by serving as a control, in that their genes are constant. “When raised together, both identical and fraternal twins (who on average share only half their genes) come as close as any two people can to sharing the identical home environment” (Glass).
However, when reared apart, they would share no environmental influences; therefore, any differences that develop between the genetically identical twins would be the result of the different postnatal environments in which they were raised. Theoretically, if there was a “well-authenticated case of identical twins reared apart between whom a dramatic difference appears should be enough to invalidate the hypothesis that ‘heredity is destiny’” (Gruber). However, finding such a definitive case has proven difficult for researchers, who have struggled to find significantly different environments and unbiased cases.
Most separated twins come from low-income families and are often raised under similar socioeconomic conditions. There is also disagreement with what constitutes similarities in both qualitative and quantitative studies of the twins, such as personality and I. Q. tests. These difficulties have not stopped scientists from continuing to pursue research of identical twins in hope of finding conclusive evidence one way or the other. Some of the essential findings from the case studies on identical twins have revealed a number of expected tendencies, as well as a few surprising trends.
Behavioral geneticist Nancy Sega has found that twins raised apart are just strikingly similar in personality to twins raised together, and that biological siblings reared apart are also more similar than adoptive siblings raised together (Glass). Julia Glass’s article references a famous long-term study of Minnesotan twins reared apart who shared almost bizarre similarities: Jim Springer and Jim Lewis, who met for the first time at age 39-and discovered they both drove the same type of Chevrolet, chain-smoked Salem cigarettes, and, as sports fans, liked stock-car racing and football.
Both had married women named Linda and then, after divorcing, married women named Betty. One Jim had named a son James Alan; the other Jim’s son was James Allan. As kids, each of the twins had a dog they’d named Toy; as adults, each had vacationed at the same three-block strip of Florida beach, practiced woodworking in his basement, and put up a circular white bench around a tree in his front yard. Although this is a very unique and special case, some researchers would argue that some of their similarities are coincidental and overlook quite a few differences between the twins.
Many critics point out that even identical twins raised together differ, sometimes significantly, especially in personality and temperament. Dr. Susan Farber believes this is a special process, known as twinning, which takes place in the unique environments that twins raised together create for one another. Often, twins deal with their unique identity problems by accentuating similarities and cultivating differences (Gruber). She also believes that twinning can occur between twins reared apart if they know of the other’s existence through letters or another means of communication.
But even Dr. Farber has stated that the best case of twin studies leaves much to be desired in terms of conclusive evidence favoring either genetics or the environment. The studies likely have ruled out any complete responsibility from one side or the other in favor of a broader debate focused on how much each is responsible during development. While the debate has shifted from exclusive responsibility to degrees of influence, other scientists have been studying how genes and environmental factors may interact and influence each other.
They have researched how the environment interacts with DNA, from drugs to psychotherapy, in order to determine whether someone will suffer from psychological disorders. This field, known as epigenetics, has finally begun to address gene interactions that were once against conventional biological wisdom. It was believed that such molecular changes occur in fetal cells but not in mature cells. Recent studies are starting to show evidence that certain environmental stimuli can lead to epigenetic changes that could trigger several psychiatric diseases (Steinberg).
Understanding and measurement of these changes could eventually indicate how the environment influences the genetic chemistry that underlies many human behaviors and psychological conditions. The two major psychological disorders being studied in the field of epigenetics are schizophrenia and depression. These conditions have been known to run in families and typically arise in adults or adolescents after puberty, when a change takes place in how the responsible gene is expressed. What causes this change is still an unknown, early studies suggest a number of environmental influences may act as a trigger (Steinberg).
Evidence has also shown physical changes in the brains of patients suffering from depression. Antidepressants have been developed to help counteract the chemical imbalances that result from these changes. However, there is still much about the treatment of psychological disorders using drugs that scientists do not fully understand. “Applying epigenetics to the brain is just beginning, but the field is ramping up as technologies to monitor molecular changes improve” (Steinberg). Ultimately, biology and genetics have proven that neither nature nor nurture is exclusively responsible for our development.
While many physical traits have definitive genetic ties and growing up in a certain culture certainly has an impact on one’s personality, modern science has shown that the interactive relationship between these influences is extremely complex. Hans Kummer gave a great analogy of the debate by saying that “trying to determine how much of a trait is produced by nature/genes and how much by nurture/environment is as useless as asking whether the drumming we hear is made by percussionist or instrument” (M. S. , M. B. ). The majority of scientists have come to accept this notion of two intricate and inseparable influences that make us who we are.
The historical nature versus nurture debate is over because science had proven the relationship to be far more complex than many scientists imagined and the phrase simply does not do that justice. The term itself has been outgrown by progress in genetics, and can no longer be simply separated into one versus the other. This lagging behind in the language of genetics has kept the futile debate alive for a long time, and often providing fuel for social agendas. Today, scientists hope that new language can better reflect modern science, and allow new questions to be presented in more productive ways.