7th Grade Science – Article Abstract 16 – 25 Points
INSTRUCTIONS: Read this article and outline its important points by answering the questions at the bottom.
----------------------------------------------------------------------------------------------------------------------------Nature and Nurture by Dr. Claudia Englbrecht. American Museum of Natural History - Sample
Essays on Genetics, Genomics, Genethics. 2010
http://www.amnh.org/learn/resources/genetics_resource1.php
"Nature versus nurture" is a phrase used widely to express the long-standing scientific debate about
whether we are mainly "made" by our genes or whether influences from the environment are more
important in our construction. Today, we know that our nature (our genes) and our environment
(which includes our development in the womb, nutrition, personal contacts, parents, friends,
experiences, the climate, etc.) together make us individuals. We are the result of the subtle
"cooperation" of genes and environment. This is why the terminology "nature versus nurture" is
misleading. It is misleading because it is not "versus," but rather "and" or "together."
Venus and Serena Williams, two sisters, are considered world-class tennis players. Is their success a
result of their similar genes, or evidence of their similar training?
There are probably only a few traits, such as hair color, eye color, and blood type that are determined
solely by genes. Other traits, such as physical condition and health, are strongly influenced by the
environment. The majority of our traits are influenced to a varying extent by our individual
environments. This is obvious in language. The French speak French with a fluency no American can
achieve.
But height is also determined by nurture; during the last century the overall height within populations
increased in almost all countries that industrialized and improved both hygiene and nutrition. This
trend is not related to changing genes. The genotype is all the specific gene versions an organism
possesses. The phenotype is the detectable outward manifestation of a genotype and is also
influenced by the environment (e.g., hair color). The genotypic composition of these populations did
not change drastically during that time. This shows that organisms have great phenotypic plasticity
(an observable change of a genetically controlled trait) for certain traits, i.e., genes produce a wide
range of phenotypes across a range of environments.
The view that most of our traits, including personality, result from genes and environment was not
always shared. Only a few decades ago, the prevalent opinion among behaviorists was that “the
human is an empty being.” Almost everything in human behavior was explained by exogenous
influences. Sound scientific studies and evolutionary theory have led to the view we have today about
the interaction of genes and environment in the development of traits. Of course, scientists are not
satisfied with the mere notion that genes and environment both affect our traits: They also want to
understand the interaction more precisely; namely, how does the environment impact special traits?
This is particularly interesting in the case of diseases, such as asthma or cancer.
Psychologists have a strong interest in determining the role of genes in the formation of our
personality, our intelligence, and our social ability. Scientists are trying to assess the so-called
heritability of a trait (not to be confused with heredity), or how much of a trait is a result of genes.
Gaining that insight is also very important for understanding the causes of mental illnesses and how
to treat them.
How does one properly measure the heritability or the impact of nurture on traits? It is not an easy
task. Humans are genetically variable, and therefore comparisons between two individuals don’t
always allow for inferences about the influence of nurture to be made. In addition, the measurement
of intelligence or social ability is a rather subjective endeavor. In order to assess the environmental
influence on traits, it is helpful to compare traits in genetically identical individuals.
The only naturally occurring genetically identical humans are identical twins, or triplets, quadruplets,
etc. There is a specific discipline dedicated to twin studies. In such studies, a few approaches can be
taken. Traits are measured in identical twins that grew up together in the same environment, and in
identical twins that were raised apart in different environments. Important inferences can be made
when comparing data from those studies with data from fraternal twins and siblings who grew up in
the same family—siblings who shared the same environment at the same time, rather than siblings
who were not exactly the same age and therefore didn’t share the exact same family experiences.
Adopted children are included in these studies, too. The adopted children serve to determine which
traits appear to be most affected by the presence of biological versus foster parents.
Intelligence
Twin studies showed that 85% of identical twins raised together and 70% of identical twins raised
apart had the same IQ. This would imply that genes have a major impact on intelligence, but how
does it work? The explanation for these results could partly be that the identical twins chose (as a
result of their genes) the same social environments in their lives even when they were raised apart
and therefore were similar in their IQs. A study of over 212 twin studies that examined the heritability
of intelligence concluded that 85 percent of identical twins raised together, and 74 percent of identical
twins raised apart, had the same IQ, compared with much lower percentages for siblings raised
together (45 percent) and apart (24 percent) (Devlin et al., 1997). This implies that genes have a
major impact on intelligence, but how do they work? One explanation for these results is that the
identical twins chose (as a result of their genes) more similar social environments in their lives than
siblings would, even when they were raised apart, and thus they had more similar IQs. A more recent
MRI study provides another explanation, pointing to a genetic influence for the size of some of the
regions of the brain involved in cognitive function (Thompson et al., 2001). Thus, twins with identical
genes are likely to produce similar brain sizes.
It is still hotly debated whether intelligence, as measured by multiple-choice tests, is determined by
nature, nurture, or both.
Aggression and Humor
According to family studies, the influence of family environment on the personality development of
children is, perhaps surprisingly, relatively minor (except in cases of severe neglect and abuse).
Environmental influences outside the family, such as school and friends, are often more important to
the development of personality. However, these "outside influences" may have more to do with genes
than it would seem at first. People might choose, or even create, environments to which they are
genetically predisposed. For example, an aggressive person is more likely to find an environment in
which arguments are likely to take place, or to create such an environment by starting fights, than a
peace-loving person might. In these cases, the assessment of whether genes or environment is more
important resembles the question of the chicken and the egg.
As for humor, a study concerned with the genetic basis of humor suggested, by comparing reactions
to Gary Larson’s The Far Side cartoon, that upbringing has more influence than genes on the sense
of humor (Cherkas et al., 2000). However, there did not appear to be a general humor factor
underlying responses to the cartoons, and no effect of age was seen.
The way genes influence our personality may be by directing the development of the nervous and
endocrine systems, and the body chemistry that rules our behavior. By comparing personality traits, it
should be possible to find links to differences in body chemistry—and in fact, more and more of these
links are being discovered.
Hopefully this short description of some of the ongoing research into the nature/nurture debate
provides an idea of how complex the development of human traits is. It should be clear that, except
for a few cases (such as some diseases), we are not solely determined by our genes. However, in the
future, the danger of genetic testing lies in the fact that other people and institutions (e.g., insurance
companies) will try to classify us, and determine our genes, so they can estimate our predisposition to
disease or even to specific behaviors.
Cherkas, L., F. Hochberg, A.J. MacGregor, H. Snieder and T.D. Spector. (2000). “Happy Families: A
Twin Study of Humor.” Twin Research 3, 17-22.
Devlin, B., M. Daniels and K. Roeder. (1997). “The heritability of IQ.” Nature 388, 468-471.
Thompson, P., T.D. Cannon, K.L. Narr, T. Erp, V. Poutanen, M. Huttunen, J. Lönnqvist, C.
Standertskjöld-Nordenstam, J. Kaprio, M. Khaledy, R. Dail, C.I. Zoumalan and A.W. Toga. (2001).
“Genetic Influences on Brain Structure.” Nature Neuroscience 4 (12).
------------------------------------------------------------------------------------------------------------------------------------1. List the title of the article, the author, where it was published, and the date it was published.
Questions: Think of two closely related pop stars, athletes, artists, or peers. If you can’t think of two
closely related people use the example given in the article of Venus and Vanessa Williams, or Eli and
Payton Manning or George Bush Senior and George W Bush.
1. Name a characteristic in these people that are the product of nature and nurture.
a. What part of this characteristic is nature and why is it shared between them?
b. What part of this characteristic is nurture and why is it shared?
2. How is intelligence a product of nature and nurture?
a. Cite the statistics that twin studies have gathered about intelligence?
3. Why are identical twins studied to learn about the effects of nurture on genes (phenotypes)?
4. Name another trait you have shared with a sibling or a parent that is also the product of
nurture.