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Ethnic Differences 1
Running head: GENETIC DIFFERENCES BETWEEN ETHNICITIES
Ethnic Differences: The Extent and Significance of Genetics
Michael Mao
Creighton University
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Abstract
This paper provides a brief summary over the findings from current studies and research
concerning genetic differences between ethnic groups. These findings can be divided up into
research pertaining to physical and intellectual disparities associated with different ethnicities.
This paper also evaluates the results of these studies, the methodology used, and the respective
limitations in an attempt to assess the relative contribution of genetics. A small discussion of
future research concerning ethnic differences along with possible societal consequences is
included.
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Ethnic Differences: The Extent and Significance of Genetics
Throughout history, perceived ethnic differences and inferiority has caused individuals of
different ethnicities to constantly fight against persecution for their freedom, civil rights, and
equality. Numerous instances of ethnic persecution are seen throughout history, whether it
involved Native Americans fighting for their right of land, African-Americans for equality, or
Jews struggling to survive during the holocaust. If past historical conflicts resulting from ethnic
differences are not an indication of the issue’s importance, then the current debates concerning
ethnic equality in all aspects of life including education, work, healthcare, and unconscious
prejudices are clearly revealing. Furthermore, increasing research on ethnic differences coupled
with the rapidly expanding knowledge of the human genome have provided the availability to
pursue research that can produce scientific evidence with concrete support for or against ethnic
differences, hence either substantiating the belief of an inferior ethnicity or the belief of ethnic
equality despite overt physical appearances. For example, many scientific articles now offer data
from studies that support the presence of ethnic differences, such as an increased presence of
Tay-Sachs alleles in Ashkenzic Jews, cystic fibrosis in North European populations, and betathalassemia in eastern Mediterranean basin populations (Neel, 2001). Although such studies are
useful for determining apparent correlations between symptoms and ethnicities, more in-depth
studies must be conducted to ascertain the influence of genetic versus environmental factors.
Numerous environmental factors such as socioeconomic, cultural, and learned behavior make
distinguishing ethnic differences based on genetics uncertain and difficult. Previous research
and scientific debates have indeed confirmed the extensive and surprisingly penetrating ways in
which environmental influences can contribute to ethnic differences in all aspects of society
through the so-called interaction between nature and nurture. However, recent research has
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increased understanding of ethnic differences by providing evidence clarifying the separate
genetic and environmental components of ethnicity. Through the examination of these recent
studies, this paper attempts to better understand and clarify the extent of genetic differences
between ethnicities as well as discuss the impact this research can have on society.
Ethnicity Term and Background
It is noted that this paper will utilize the term ethnic rather than the term racial.
Traditionally, the term race has been used to distinguish biologic and genetic properties of
individuals, with skin color being a large determining factor for classification. However, as
Flaskerud (2000) notes, the term race is an incorrect term because it has ceased to exist and thus
the use of the term is inaccurate and imprecise. Consequently, the term ethnicity will be favored,
where ethnicity is generally defined as a shared sense of people hood in a group of individuals
based on shared geographic origin, language, religion, customs, kinship patterns, and observable
characteristics and phenotypes due to environment and genetics. The five broad ethnic groups
commonly identified in the United States consist of “African Americans, Hispanics/Latinos,
Asian Americans and Pacific Islanders, American Indians and Alaskan Natives, and White or
European Americans” (Flaskerud, 2000). In addition, it is made known that due to the vast
majority of research that has focused on ethnic differences between African Americans and
Europeans, the topic of this paper may be similarly focused.
Current studies have shown that modern humans evolved in Africa 200,000 years ago,
while contemporary human races are estimated to have differentiated at approximately 110,000
and 41,000 years ago through the process of evolution (Rushton, 1995). Rushton further shows
that there is indeed a genetic difference between ethnicities, yet these ethnic differences account
for only four percent of the entire human genome. The extent of genetic differences between
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ethnicities is affirmed by Feldman (1997), who notes that less than 15 percent of the distinctions
observed in ethnicities are between populations, while the remaining 85 percent are found within
populations. Despite the relatively small genomic difference, a wide variety of individual
characteristics are attributed to these ethnic differences. Research on ethnic differences tends to
fall into two categories: physical differences and intellectual differences. Hence, recent research
on physical differences between ethnicities can first be examined followed by an examination of
intelligence differences.
Physical Differences between Ethnic Groups
A recent topic that has received a great amount of research concerns differential ethnic
susceptibility to a disease. A good model of a verified physical and genetic difference between
African Americans and Europeans concerns the genetic polymorphism associated with the sickle
cell anemia gene and hemolytic anemia of glucose-6-phosphate dehydrogenase deficiency, G-6PD (Neel, 2001). Sickle cell anemia is caused by a homozygosity nucleotide substitution in a
gene coding for beta hemoglobin found in chromosome 11. The sickle cell gene originated in a
tropical environment where Plasmodium falciparum malaria is prevalent and a significant cause
of morbidity and mortality. When the sickle cell gene is present in individuals in a homozygous
state, it is often fatal. However, when the trait is heterozygous in an individual, it imparts
protection to the individual from malaria due to decreased ability of the parasite Plasmodium
falciparum to grow. Consequently, natural selection would have selected for this sickle cell gene
for African-Americans in tropical climates, thus explaining the ethnic difference resulting in
Europeans possessing a greater susceptibility to malaria. Furthermore, this theory gives a
potential explanation for the high mutation rates in genes prevalent among African Americans in
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Africa. In G-6-PD, similar findings have revealed that genetic differences in ethnicities exist as
a result of natural selection (Neel 2001).
Mortality and Associated Diseases
In the past 30 years, there has been continuing debate over mortality differences between
African-Americans and Europeans, where past studies show that African-Americans seem to
have lower mortality rates at older ages, hence a longer life, despite data showing that AfricanAmericans may be receiving less healthcare (Martin, 1997). The mortality rates between ethnic
groups was further studied by Elo and Preston (1997), where the two ethnic groups receiving the
greatest attention in terms of mortality rates are between African-Americans and Europeans.
Data have shown that even though African-Americans have a higher mortality rate at a younger
age, they have a lower mortality rate at an older age when compared to Europeans (Elo &
Preston, 1997). Elo and Preston suggest that this crossover of mortality of African-Americans
surpassing Europeans can be attributed to the theory of survival of the fittest (1997). This study
would thus infer that younger and weaker African-American individuals subject to harsher
environmental conditions than Europeans would have higher mortality rates at an earlier age,
thus leaving the stronger African-Americans to reach an older age and surviving longer than the
mix of weak and strong Europeans. Despite these data, one must acknowledge the limitation of
this study, where one possible explanation for the observed results is due to misrepresentation of
age in African-Americans due to poor vital statistics and census data.
Mortality rates for other ethnic groups are also reported, though there has been less
scientific evidence providing explanations for the observed rates. Nonetheless, it is noted that
Hispanics generally have a lower mortality rates when compared to Europeans, and this
difference increases with age. Asian Americans and Pacific Islanders have the lowest mortality
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rate of all the groups (Elo & Preston, 1997). These general mortality differences suggest genetic
differences between ethnic groups.
Explanations for these differences in mortality rates can be further verified by examining
differential ethnic susceptibility to diseases that can lead to earlier mortality. One such disease is
congestive heart failure (CHF). This research was conducted at a financially equal-access health
care system, which is nationwide and federally funded so that healthcare is provided to all
individuals without restrictions due to economic reasons, such as insurance status or inability to
pay. Consequently, the research parameter aids by decreasing the environmental variables that
may affect the results. The study found that African-Americans on average have a higher
prevalence of congestive heart failure than Europeans. Furthermore, evidence demonstrated
significant differences between African-Americans and Europeans in regard to short-term and
intermediate-term mortality after CHF, where African-Americans possessed a lower mortality.
One explanation proposed for this result is that African-American patients may have a greater
susceptibility to sodium retention associated with hypertensive heart disease, hence requiring
hospitalization at earlier stages of the disease (Deswal, Petersen, Souchek, Ashton, & Wray,
2004). This hypothesis hence suggests that genetic differences in ethnicities leads to increased
susceptibility to sodium retention. Further analysis of the data also showed that the AfricanAmerican ethnicity was an independent predictor of improved survival after hospitalization.
Limitations associated with this study are that African-American patients were generally younger
and had less comorbidities when compared with European patients, though the researchers
attempted to take this factor into account in their analysis (Deswal et al., 2004).
Further evidence related to cardiac diseases that both supports and contrasts the
conclusions from the previous study showed that African-Americans are more likely to be
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diabetic, hypertensive, and possess a higher rate of chronic renal insufficiency. However, they
are also less likely to have coronary artery disease or hypercholesterolemia than Europeans.
Furthermore, in African-Americans, lesions occurred more often in the left descending coronary
artery (Leborgne et al., 2004). Leborgne et al. (2004) state that the deleterious effects of diabetes
and hypertension may indirectly cause coronary microcirculation and hence lower left
ventricular ejection fractions. Hence, this finding exemplifies the complexity of the role of
genetics and the environment, where genetics increases the likelihood of ethnic individuals
acquiring diabetes by interacting with an environment that promotes the formation of the disease
as well. Consequently, diabetes can increase genetic susceptibility to coronary microcirculation
caused by ethnic differences in the prevalence of genes. Contrary to the above study, after
controlling for baseline ethnicity differences, ethnicity was found not to be an independent
predictor of in-hospital major adverse cardiac events. The limitations involved the use of an
older population for African-Americans and that African Americans were less often referred for
coronary revascularization than Europeans (Leborgne et al., 2004).
Further Physical Ethnic Differences
In addition to these ethnic differences in disease susceptibility and mortality caused by
CHF and cardiac related problems, there are numerous studies that have found different physical
aspects that differ between ethnicities. One such study involved preterm birth rates, where
significant ethnic differences in the rate of low birth weight and preterm babies were detected
(Preterm birth, 2004). African-Americans were associated with the highest percentage of infants
born with low birth weight and very low birth rate when compared to Native Americans, AsianPacific Islanders, Hispanics, and Europeans. It was noted in the study that this attribution of
genetic factors to this phenomenon is limited by environmental factors that might play an
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indirect role through assisted reproductive technology, which would cause multiple gestations
and hence decreased birth weight (Preterm birth, 2004). Another study stated that African
Americans get sick faster from smoking (African Americans, 2004). Studies involving advanced
chronic obstructive pulmonary disease have found that African American patients who start
smoking later in life and smoked less still have the same disease severity at an earlier age when
compared to European patients (African Americans, 2004). One other general study involving
ethnic differences noted that ethnic differences in the United States showed African-American
babies possessed shorter gestation period than European babies, where 51 percent compared to
33 percent are born respectively by week 39 (Phillipe, 1996). Furthermore, standardized tests
show that African-American babies mature faster physically in muscular strength, coordination,
and locomotion, with Europeans and then Asians following behind. One other difference noted
was that African-American college students have a 19 percent higher testosterone rate than their
European counterparts (Philippe, 1996).
Intelligence Differences between Ethnic Groups
The second general category of research concerning ethnic differences that has received
vast attention concerns intelligence and its correlation to genetics and ethnicity. Previous studies
have often attempted to correlate ethnicity, head size, and intelligence to account for the
difference in IQ test scores between European and African-American scores. For instance,
Rushton (1995) revealed a repeated difference in cognitive ability between ethnicities. However,
more recent research has provided many arguments and evidence against such theories. One
study conducted by Kamin and Omari (1998) found a number of calculation and other associated
errors in previous studies of external head measurements made between African-American and
Europeans. These findings would invalidate the conclusions of several studies that purported a
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correlation between ethnicity, head size, and intelligence. The research further commented that
differences in body size, nutrition, and social class would all have effects on head size and IQ.
The study concluded that differences in external head dimension, which is small and can be
affected by differently shaped heads, are inconsistent and thus its correlation to intelligence is
likewise minimal. Hence, data on ethnicity, head size, and intelligence cannot explain the
observed ethnic differences in IQ tests between African-American and Europeans (Kamin &
Omari, 1998). It follows then that ethnic differences caused by genetics that determine different
head sizes would have no influence on intelligence.
Arguments against the connection between ethnicity and intelligence also hold that no
formal mechanism has been identified that could explain how the complex attributes associated
with intelligence could be connected with the behavior of one ethnic group. For instance, natural
selection that testifies to the environment shaping an ethnic group’s intelligence is not a good
hypothesis since it is untestable. Furthermore, another argument against attempting to correlate
intelligence to ethnicity is the presence of a fundamental difference between a simple trait such
as skin color, determined by only a few genes, and a complex attribute such as intelligence,
which depends not only on a multitude of unknown genes but by the environment (Olson, 2001).
Discussion and Implications
The implications of these studies are significant and very diverse. Whereas the research
pertaining to physical ethnic differences are concerned, it seems that each of the studies gave
results that showed no clear superiority or inferiority between ethnic groups. For instance, the
study on the prevalence of sickle cell anemia among African-Americans reveal that even though
Europeans are more susceptible to malaria, they do not incur the associated disabilities and
dangers of sickle cell anemia (Neel, 2001). Furthermore, the studies concerning mortality and
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associated factors, such as CHF and cardiac problems, reveal that despite variations that can be
associated to potential genetic differences between ethnicities, such studies do not disregard the
influence of environment. The studies concerning ethnic differences in preterm babies, greater
smoking risk, and childhood development and rates of hormone release all reveal deficiencies in
providing concrete genetic evidence for the observed ethnic characteristics.
Furthermore, the methodologies of these studies contain many limitations, a few of which
were explicitly noted in this paper. One example concerns Philippe’s study that stated that a
higher testosterone level was found for certain ethnicities (1996). For a more accurate analysis,
it seems that the study should include a greater and more inclusive sample size than college
students and United States veterans (Phillipe, 1996). In addition, limitations associated with
methodologies used can also be exemplified by Deswal et al. (2004), where it was hypothesized
that European patients may have systematically received inferior healthcare. However, a recent
study in the Veterans Health Administration has not supported the hypothesis through a study of
inpatient treatment and discharge care for CHF, Medicare quality of care, and discharge rates
from hospitalization. Nonetheless, it was still noted that certain aspects of the study, such as the
small differences concerning the use of outpatient services compared to urgent care emergency
room visits between African-Americans and Europeans, could not be addressed adequately by
the study. One explanation suggested for the study’s results may be the lack of social support
available for African-Americans (Deswal et al, 2004).
In regards to the studies concerning intelligence, it seems that recent studies have largely
refuted the previous methodologies used to observe measure intelligence among ethnicities, as
well as discounted the findings of a correlation between ethnicity and intelligence. Furthermore,
factors such as education, personal experience, social class, diet, and numerous other
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environmental influences have far-reaching effects on perceived ethnic differences. Hence,
despite science best efforts, it may never be possible to fully assign a trait as fully genetic or
environment. The significance of the interactions between genetics and environment should not
be overlooked or viewed as static, which is evident when Neel (2001) noted that diseases, such
as diabetes, is influenced by modern civilization as well as genetics, and that the presence of a
familial nature of a disease does not necessarily mean a genetic cause. One other limitation
involves language and culture differences between the patient and the doctor, where culturebound descriptions of symptoms may cause misdiagnosis, and thus skewed data from a general
ethnicity group (Flaskerud, 2000).
Future Research and Conclusions
More systematic studies on ethnic differences can already be noted by the recent deal
between SNP Consortium and Orchid BioSciences in order to further determine the frequency of
genetic differences among ethnic groups in the United States (Orchid makes, 2000). In addition,
new research has begun in the area of pharmacogenetics. Pharmacogenetics concerns the genetic
and inherited component of variability in drug efficiency, toxicity, and disposition on
individuals. It has previously mainly used geographic and ethnic differences for classifying drug
responses. In addition, pharmacogenetics has commonly treated ethnicity as a variable in the
evaluation of clinical studies. However, new studies have revealed that chromosome one
markers were more efficient in identifying individuals with different drug-metabolizing enzyme
single-nucleotide polymorphisms (SNPs), a source of genetic variability, than basing solely on
ethnic or geographic differences (McLeod, 2001). Consequently, evidence has arisen that
genetic differences in individuals are far more consequential than skin color or geography
(McLeod, 2001). Other articles support this contention by noting that researchers often attribute
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observed differences in drug response to ethnic groups rather than inherent genetic differences,
which is a far greater factor than ethnicity (Genes, 2001). It seems that a future research
direction should thus aim toward shifting from designing drugs based on ethnicity to
individuality. Thus, with the growing knowledge and technology in genetics, it may soon be
feasible to develop an economical method to assess an individual’s genotype followed by the
application of the most effective drug based on genotype data, which would prove much more
effective than simply basing on the generalization of ethnicity. Furthermore, it currently seems
that future research should attempt to be more coordinated with each other so that the extent of
genetic contributions to ethnic differences can be determined precisely with confidence.
Currently, it appears that the research is a little scattered, thus adding to the difficulty of any one
research study of examining a topic in enough detail to determine explanations behind observed
data. Organizing ideas such as the evolutionary strategy discussed by Hama (2000), where
ethnic groups are characterized as either possessing r strategy, high rate of reproduction and low
investment on offspring, or K strategies, which involves low rate of reproduction and high
investment in offspring, should be tested first so that it may serve as a foundation and cohesive
force for future research.
In conclusion, current research seems to show that contrary to past beliefs, no ethnic side
is held superior to another. Although genetic differences may be present, they do not generally
favor one ethnicity over another. These results are significant because they can affect society at
all levels. If there was a significant ethnic difference based on biology and genetics, then society
could be affected in law and policies. For instance, society could see a legislative policy that
promoted a stronger affirmative action, which may thus disadvantage certain ethnicities. In
addition, despite the best attempts of society to promote equality between ethnicities, scientific
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evidence in favor of a significant genetic ethnic difference could also result in unconscious
prejudice, that will further increase the subtle, environmental ethnic prejudices that society is
struggling to eliminate. Consequently, future research on ethnic differences must be careful to
examine all issues completely before making hasty declarations, as evidenced with previous
studies declaring a perceived correlation between head size, intelligence, and ethnicity. The
dangers associated with such applications of recent findings that were not adequately confirmed
is seen when certain doctors no longer treated African-American patients for chronic heart
failure since a study showed that the drug was reported to be less effective for these ethnic group
of patients, whereas other research has shown that such a ethnic generalization is erroneous
(Genes, 2001). One may suggest that society should continue to focus on changing its structure
to promote greater ethnic environmental equality. In closing, it is helpful to be reminded that
geneticists have never found a genetic marker that is of one type in all the members of one ethnic
group and of a different type in all the members of another ethnic group (Olson, 2001). This is
substantiated by the fact that humans and chimpanzees have 99.85 percent similarity with
humans. Different ethnic groups, based on gene alleles in studies, can be shown only to have
1/25 to 1/60 of that between the human and the chimpanzee (Neel, 2001). Hence, keeping this
research in perspective, these studies represent only a small area of the overall research
concerning the human genome.