Nature and Nurture the Relatively

¶ … 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).

Twin Studies

The quality of resources available to siblings (such as food, medicine, educational opportunities, etc.) is generally very similar within biological families (Gerrig & Zimbardo, 2007; Rutter, 2006). To the extent these factors contribute to the development of behavior, it is extremely difficult if not impossible to identify their connection to behavior in any way that distinguishes it from biological factors because siblings usually have access to identical or very similar resources as well (Gerrig & Zimbardo, 2007; Rutter, 2006).

In that regard, some of the most fascinating data into the dual influence of environment and genetics on human behavior has come from twin studies (Gerrig & Zimbardo, 2007; Rutter, 2006). Specifically, the fact that twins are sometime separated at birth and raised by completely different families in very different situations and circumstances provides a natural laboratory for inquiries into the relative influence of genetic predisposition as compared to that of external environment and experiences (Steen, 2006).

Consider that in empirical studies, researchers have established that among identical twins, the development of specific diseases, such as schizophrenia in particular, in one twin corresponds to a one-third probability of the same disease developing in the other twin (Steen, 2006). Likewise, the anecdotal evidence of identical twins is sometimes even more dramatic, such as exemplified by cases where twin brothers were separated at birth, raised in different families in different cities, only to meet by accident as adults and find out that they have chosen identical careers, recreational hobbies, and even married women with the same first name (Gerrig & Zimbardo, 2007).

The Complexity of Differentiating the Character of Difference