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Human growth and development is an important aspect in human life. Conventionally, it describes the physical, emotional, or psychological and cognitive transformation in human life. In addition, it is a complicated process controlled by both environmental and genetic aspects (Bronfenbrenner 3).
Throughout human history, research has continually debated on several aspects of human life and development aiming at identifying the influence of genetics and the impact of environment on personal human development bringing nature and nurture terms into regular controversies.
According to McGue and Bouchard, adoption and twin studies have significantly indicated that behavioral traits are transmissible (1). On the other hand, Bouchard argues that environmental factors have also been influential in the development of humans, though such factors are most effective in individual intelligence quotient (148). However, both are essential.
These endless debates on human development have important inferences on theories and researches that are encompassed in psychological studies with human behavioral traits becoming the focus. Therefore, this essay seeks to examine whether human development and behavior are due to nature or nurture.
Nature: genetic influence on personal development
Nature has dominated several prospective studies on its influence on human growth and development. In this context, the word nature simply stands for the ways in which biological phenomena influence personal development and behavior (Gottesman and Hanson 10.6). Hereditary aspects of human beings are associated with behavioral characteristics in human beings.
Heredity simply describes how individuals acquire characteristics through a biological process involving genes. Different projects, including the Human Genome Project, demonstrate that DNA components found in human beings are identical to all humans with an estimated percentage of 9.9 percent resemblance. Gottesman and Hanson assert, “Factors that influence DNA methylation are huge and include such things as developmental processes, diet, and viral infections” (10.5).
Due to this DNA sharing aspect, biological studies, including famous theories conducted on evolutionary propositions have some evidence that almost all animals share similar characteristics with their respective ancestors. With studies and theories carried out to examine the impact of nature on the personal development and personality traits, heredity is an important factor in the development.
Behavior genetic studies and nature
In several occasions, human biology and psychologists have concentrated on what aspects allow human beings to have similar characteristics. Based on the focus of this study, gene, which is a biological component of growth, influences behavioral characteristics in human beings. In specific attention to genetics perspective, genes are natural elements that shape hereditary.
Genes pass on from one generation to another, with the likelihood of offsprings adopting traits embedded in their blood relation (Bouchard 149). Scientifically, genetic influences on personal traits and development resulted from studies of two twins, commonly known as behavior genetic studies. Behavior genetic studies were initiated by Jim Springer and involved separation of two twins, namely Jim and Lewis after five weeks of their age for a considerable number of years.
Thereafter, Springer reunited the boys after thirty years of their separation. However, during the course of their observation, the twins had similar behavioral mannerisms ranging from their hobbies, emotions, thinking and even dislikes. This study concluded that nature is automatic and biological phenomena influence behavioral traits.
Several years ago, behavioral genetic studies conducted by Tyron in the year 1940 also formed the basis of discussion of the influence of biological phenomenon on behavior. Tyron took an approach of selective breeding animals. The researcher identified two rats with certain similarities coupled with their performance on maize (Thompson, Cannon, and Toga 34). Tyron mated the rats according to their brightness in color with the bright mating the bright and the dull, vice versa.
After repetitively carrying out this procedure for at least twenty-one generations, Tyron had two rats so different from each other. Tyron later tested their performance on maize and realized that their performance was similar to their initial offsprings. The science of Tyron can be significant in explaining how human beings adopt some behavioral characteristics from their parents (Thompson, Cannon, and Toga 34).
Based on several observations made on the academic performance of pupils compared to that of their parents, it is clear that genetics influence the growth and behaviors of individuals. Under these practical behavior genetics studies, biological phenomena affect the development and consequent behavior of beings, which are human beings.
Studying family traits and behaviors is also a common way of identifying how genetics affects the behavioral traits of individuals or population. In family studies, researchers attempt to estimate generic impacts between individuals by comparing close relatives to examine how they resemble each other on particular distinctiveness. According to Gottesman and Hanson (10.7), through studying families, researchers have concluded that there are certain traits that are eminent in families.
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Estimates reveal that about 25 percent of the grandchildren examined in studies have traits resembling those of their grandparents. In their research, Lenroot et al. assert that, to examine the relationship between genetics and behavioral traits, “quantification is possible by examining covariance patterns between family members of different levels of genetic relatedness” (164).
Through family studies, genetic influence on personality traits is eminent in talents and abilities possessed by individuals. In several cases, there are possibilities of offspring sharing similar human skills, including artistic or musical talents and sportsmanship.
Genetic influence in is also commonly examined in hereditary factors that are passed through DNA sequences. Scientist has studied several hereditary diseases and concluded that genetics consequently influence personal behavior traits. Psychologists have also studied this relation and identified that generic influence on behavior traits account to about 40-50 percent through heritability.
Bouchard asserts, “Schizophrenia is the most extensively studied psychiatric illness, and the findings consistently suggest a very high degree of genetic influence (heritability of about 80), mostly additive genetic influence, with no shared environmental influence” (149). Apart from schizophrenia, hereditary factors of genetic are also eminent in diseases such as phobias, panic disorders, depression, heart diseases, and even cancer.
Thompson, Cannon, and Toga assert, “Heritable diseases and behavioral traits arise from DNA variations passed on from parents to their offspring” (524). Therefore, by studying hereditary diseases, evidence-based research depicts that genetics influences human behavior bypassing behavior traits from one generation to another in close blood relationships.
In a bid to delve further into the nature issue, the twin studies comprehensively used to examine how heredity and environment affects human development play essential roles. According to Gottesman and Hanson (10.13), genetically tested experiments and data analysis of twins brought up together in a similar environment give an important view on the impact of nurturing on personal development and behavioral characteristics.
Twins’ studies, which are commonly referred as Minnesota personality studies, examined over 217 pairs of monozygotic (MZ) twins, meaning that the twins resulted from an ovum fertilized from one sperm cell and about 114 pairs of dizygotic (DZ) twins, meaning that they were born of separate sperms fertilizing separate eggs, grew together.
On the other hand, 44 MZ and another 27 DZ pairs grew separately (Thompson, Cannon, and Toga). Researchers on this study observed that heritability in these twins provides an average of almost 48 percent. After undergoing several discussions and argument, this study concluded that genetic factors contribute significantly to people within a given group
Nurture: Environment and personal development
Nurturing or fostering affects personal development and behavioral traits. How a person grows through different experiences consequently determines the outcome of personal behavior. According to Bouchard (148), behavioral interconnections are eminent within societies or communities with environmental connections among individuals, families, or even groups, particularly in political influence and economic power.
Nurturing as used in several kinds of literature denotes a process by which individuals grow. Behavioral traits found in parents are most likely to be eminent in children through adoption. Cultural aspect is among the many ways through which researchers conclude that nature affects an individual’s behavior.
Culture has significant power to determine a person’s behavior depending on the parental influence and extent of their adoption to culture. Taking an example of a community that strictly observes religion or certain rituals, offsprings in this society are likely to adopt the culture and the sequence continues. Bouchard asserts, “Membership in a specific religious denomination is largely due to environmental factors” (151).
Environment has been so influential in personal traits and development. However, in most cases, environment influences an individual’s life in the early ages up to almost 20 years. Factors including cultural backgrounds, social affiliations, and physical environment become important aspects that help in examining the impact of environment on personal behaviors.
In the study undertaken by Lenroot et al., “environmental factors may be causes of downstream behavioral and cognitive function and may become more prominent relative to genetic factors as socioeconomic conditions worsen” (170). As human beings develop, they expose themselves to different environmental factors that tend to impact on their behavioral traits.
According to Emde and Hewitt, this scenario is quite eminent in children who adopt behaviors found in their parents (23). It is common to find children taking alcohol due to the influence of their family members/parents or close relatives having the tendency of alcohol taking and very common to find children becoming religious following their parental roots.
Behavior Genetics Studies and Nurture
In the context of nurture, the twin’s studies contain a vital but hidden massage that researchers normally ignore. According to McGue and Bouchard, data acquired from this study provides significant evidence in the impact of environment on personal development and behavior traits (10).
The pro-nurture conclusion hinges on two main observations. Despite carrying out several studies with regard to hereditary impact on personal development and personal traits, researchers have not considered the fact that genetic differences contribute to about 50 percent or even less. This aspect automatically implies that environmental factors are entirely responsible for the remaining percentage. On the same note, it is possible to find family members having different traits, despite coming from the same blood.
Researchers commonly observe this aspect in some children who grow together and possess extremely different characteristics. Based on the evidence drawn from this argument, it is common that regardless of their relationship, there are no possibilities that two siblings live together throughout their lifetime.
Therefore, in the process of separating and living in different environments, people’s surroundings are most likely to be responsible for their differences in their behaviors.
However, culture is a powerful aspect in determining growth and development; thus if brought up under the same environment sharing the same culture, they are most likely to have similar traits (Lenroot et al. 165). Probably, siblings living together in a shared environment including having the same parents, attending the same schools, living in the same home, taking the same meals, and even attending similar functions possess different traits.
On the other hand, siblings might live in a non-shared environment including being raised differently by their parents, occupying different environments, or even having different sportsmanship and finally differ in their behavior traits (Bouchard 149). This scenario definitely explains how the impact of the environment to human behavior is unique with people adopting different traits based on their environmental experiences.
Complications between nature and nurture
As researchers struggle to identify the transparency between nature and nurture, the complication between the two aspects still exists. Several prospective studies carried out on the subject are making the complication worse. Contrary to other studies carried out, Urie Bronfenbrenner and his colleague Stephen, in the year 1994, proposed a bio-ecological model to stretch the argument on the aspects of nature and nurture.
According to Bronfenbrenner, at birth, mothers bestow newborns with genetic predispositions (6). The predispositions only have the ability of influencing the behaviors of the children later in their old age with life experiences playing an important role on the behaviors at that age.
These predispositions have a component of intelligence. Taking into account the realities of life, some children are raised in poor families and thus, they undergo stress and frustrations, which might limit them from realizing their potential. On the other, hand some children are raised in stress-free homes with many opportunities to explore their abilities. Finally, one only wonders how these predispositions can prove genetic influence on human behavior.
The nature vs. nurture debate has been unique in its arguments between natural development and environmental influence on human development and personality traits. However, both nature and nurture have a portion to share in human development, especially in determining personal traits of individuals, though studies reveal that their influences are non-independent (McGue and Bouchard 6).
Based on nature, scientists and psychologists have continually examined the influence of genetic factors on the development. Scientifically, genetic influences on personal traits and development resulted from studies of two twins.
The studies provided a significant proof about the hereditary factor with the possibility that offsprings adopt behavioral traits from their parents naturally (Thompson, Cannon, and Toga 523). On the other hand, scientists, philosophers, and psychologists still argue that environment or nurturing aspect has a greater influence in development of human behavior characteristics.
The argument on nurturing aspect is that, if all genetics prove that it is responsible for human behavior, then why does it only cover 48 percent on genetic influences. Family studies propose that there exist possibilities that children can never live together in their entire life, and thus changes observed in them is due to environmental influences. However, as prospective research continues to dominate, probably controversies between the two aspects might never end.
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Bronfenbrenner, Urie. Making Human Beings Human: Bio-ecological Perspectives on Human Development. New York: Sage Publishers, 2004. Print.
Emde, Robert, and John Hewitt. Infancy to Early Childhood: Genetic and Environmental Influences on Developmental Change. New York: Oxford University Press, 2001. Print.
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