DNA science and the nature-nurture debate in human behavior

¶ … Nature and Nurture

The relatively recent development of DNA sciences have contributed greatly to our understanding human behavior, physiology, and heredity. Genetic sequencing and the myriad offshoots of the earlier-than-expected Human Genome Project shortly after the turn of the century have already revolutionized many forms of medical treatments and generated forensic techniques capable of identifying specific individuals with unprecedented accuracy and from an ever-widening range of genetic tissues.

Likewise, the statistical probability of many specific diseases and other physiological conditions can now be identified for the individual and it is likely that within a relatively short time, it will be become routine to produce a virtual representation or "file" for every person containing his or her health and medical profile. In the next decade, microchips of our entire genetic profiles will probably fulfill the same roles in general medicine as dental X-rays have traditionally in modern dentistry.

To a large degree, DNA science has also ended the traditional debate among psychologists and behaviorists on the relative importance of the genetics of heritability (nature) or of external environmental influences (nurture). Previous arguments concerned the one-dimensional inquiry into which set of factors was more responsible for human behavior. Meanwhile, the modern approach made possible by DNA sequencing as well as various brain imaging techniques has allowed a much more comprehensive and detailed appreciation for the specific contributions of genetics and of other natural physiological differences among individuals. The latter, in particular, allows researchers to directly view specific differences in brain structures and neural architecture and to accurately test specific hypotheses of relationships between brain structure and behavior. However, rather than "ending" the traditional debate, the evolution of DNA sciences has made possible new technologies and a much wider range of possible inquiries into exactly how human behavior relates to biology and even the complex processes through which environmental influences change physiological development as a mechanism for incorporating elements of the external environment into human behavior and adaptability.

-in natural world -- impact of modern DNA science -- framed as debate because of one-dim

The Classical Argument over Nature and Nurture

Animal Studies

Some of the anecdotal evidence of the tremendous importance of heredity on behavior is undeniable and it is perfectly understandable why it generated very strong assumptions that human biology and external behavior is strictly determined by genetic factors. For one thing, there are the many obvious similarities between parents and their children as well as between children and previous generations of ancestors, such as in relation to the physical and behavioral traits commonly referred to as "skipping" generations.

In that regard, early 20th-century experiments into primate behavior demonstrated conclusively that some traits, such as shyness and fearful timidity as opposed to confidence and boldness are profoundly influenced by maternal behavior rather than predetermined by genetic propensity (Gerrig & Zimbardo, 2007; Rutter, 2006). In those series of experiments, Rhesus monkeys adopted the psychological and behavioral traits of whichever mother provided a behavioral "model" during the formative period of the development of their psychological style (Gerrig & Zimbardo, 2007; Rutter, 2006).

Typically, when the infants of confident dominant mothers were placed with insecure fearful mothers, the infants presumed to have the genetic propensities of their mothers adopted the behavioral characteristics of their surrogate mothers. Similarly, infants of insecure mothers placed with confident surrogate mothers exhibited much greater similarities to the behavioral mannerisms and reactions of their surrogates than to the behavioral mannerisms and reactions of their natural mothers who contributed to their genetic makeup (Gerrig & Zimbardo, 2007; Rutter, 2006).

Nevertheless, both empirical studies and age-old anecdotal observations make it impossible to deny that biology also contributes tremendously to individual physiology and external behavior. Therefore, the question arises about exactly how much of the behavioral similarities between different generations within the same family are attributable strictly to genetic factors and how much are they functions of exposure to similar treatment and foundational experiences.

That is simply because individual in the same family are much more likely than unrelated individuals to share similar foundational experiences by virtue of their exposure to similar parenting and resources in their immediate environment throughout their early lives (Gerrig & Zimbardo, 2007; Rutter, 2006). Just as Rhesus monkeys tend to adopt maternal behaviors and elements of personalities of their mothers irrespective of their genetic inclinations, so do human infants and growing children and adolescents internalize and adopt various aspects of the behaviors and reactions exhibited by their parents and other significant adult behavioral role models in their lives (Gerrig & Zimbardo, 2007).

The Complexity of Differentiating the Character of Difference

The prospect of differentiating or quantifying the undeniable influence of biological predestination and behavioral characteristics that are attributable to external environment is further complicated by the degree to which external environment and experience result in structural physiological changes, such as in the neural architecture of the human brain (Steen, 2006). A large volume of empirical studies has demonstrated the manner in which traumatic experiences, for one class of examples, permanently change subtle elements of the structure of specific regions of the brain and alter important aspects of hormonal and other strictly physiological responses thereafter (Gerrig & Zimbardo, 2007; Steen, 2006). Once those neural architecture and physiological responses develop, it is impossible to identify their source (i.e. whether they were originally functions of heredity or external environment) retrospectively (Steen, 2006).

Conclusion

Prior to the era of modern scientific methods and the technological research tools and technologies of contemporary researchers, it was understandable why the nature/nurture debate generated arguments that substantially disputed or at least discounted the influence of one another on human behavior. However, in much the same way that 20th-century physicists demonstrated that electrons are better represented as a "probability cloud" rather than by models depicting individual particles occupying specific points in space at a particular time, modern psychological methods have demonstrated that the distinction between nature and nurture involves a much more complex multi-dimensional analysis. Ultimately, the answer boils down more to probabilities than to absolutes, just as in the case of electrons within atomic structure.