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The Meaning of Race in Medicine 12th Annual Summer Public Health Research Videoconference on Minorit

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Title: The Meaning of Race in Medicine 12th Annual Summer Public Health Research Videoconference on Minorit


1
The Meaning of Race in Medicine12th Annual
Summer Public Health Research Videoconference
on Minority HealthUniversity of North Carolina
at Chapel HillSchool of Public HealthJune 26,
2006
  • Dr. Joseph L. Graves, Jr.
  • Dean, University Studies Professor of
    Biological Sciences, North Carolina A T State
    University.
  • Fellow, American Association for the Advancement
    of Science

2
For a fuller treatment see
  • J.L. Graves, The Emperors New Clothes
    Biological Theories of Race at the Millennium,
    Rutgers University Press, 2001, 2005 The Race
    Myth Why We Pretend Race Exists in America,
    Dutton Press, authors preface to the soft cover
    edition, 2005.

3
Note on Definitions Biological Race
  • morphology (phenotype)
  • Geographical location
  • Population based (frequency of genes)

Socially Constructed Race Arbitrarily utilizes
aspects of morphology, geography, culture,
language, religion, etc. in the service of
a social dominance hierarchy.
4
Carolus Linnaeus - 1735
  • Introduces binomial classification system for
    organisms. He describes four sub-species of
    humans Homo sapiens americanus, the Americas
    Homo sapiens europaeus, Europeans Homo sapiens
    asiaticus, Asians and Homo sapiens afer,
    Africans.
  • He did not explain how or why these groups are
    different. He also includes Homo sapiens
    monstrosus, which included people with
    deformities, mythological giants, and the
    Khoikhoi people of southern Africa and Homo
    sapiens ferus, which described wild children
    found abandoned in forests.
  • Relies on morphological/behavioral features,
    Europeans are gentle, optimistic and inventive,
    while Asians are stiff and greedy.

5
Naturalists of the 19th century naturalists used
morphological traits to classify races
  • Darwin doubted whether human races were real.
  • Describes the racial multiplication problem, 2
    63 races named.
  • Calls human races, protean or polymorphic, in The
    Descent of Man, 1871.
  • Darwin pointed out that most of the physical
    differences noticed by naturalists could not have
    any significance, if so they would have been
    removed by natural selection.

Charles Darwin
6
Linneaus and the 19th century naturalists were
wrong because phenotypic characters are
discordant.
  • The physical features used to define Americas
    social races do not reveal our evolutionary
    history, Cavalli-Sforza and Edwards 1964, and
    Montagu 1974.
  • Genes that control skin color are not linked to
    those that determine skull shape or body
    proportions.

Fig 2.2.3, Cavalli-Sfroza, Menozzi, and Piazza.,
1994
7
Populations have different combinations of
physical traits.
  • The failure of physical variation to define
    races occurs because different portions of the
    genome are selected by different factors in any
    given environment.
  • For example, solar intensity may change
    consistently along a N S gradient, this may
    impact some genetic systems, but not others.
  • Meanwhile, other portions of the genome may be
    impacted by the presence of a specific parasitic
    disease, different diets, different rain fall, or
    altitude.

8
UNESCO Statement of 1950
By 1950 serious doubt existed concerning both
morphological and geographical conceptions of
race.
From the Preamble
  • Racial doctrine is the outcome of a fundamentally
    irrational system of thought and is in glaring
    conflict with the whole humanist tradition of our
    civilization. It sets at nought everything that
    UNESCO stands for and endeavors to defend. By
    virtue of its very Constitution, UNESCO must face
    the racial problem
  • In the body From the biological standpoint, the
    species Homo sapiens is made up of a number of
    populations, each of which differs from the
    others in the frequency of one or more genes

New York Times, July 17, 1950
9
Population subdivision is weak in humans.
  • Compared to other large bodied mammals, humans
    have little genetic differentiation between their
    populations.
  • Humans have considerable genetic overlap across
    the genome -- We have also maintained relatively
    high levels of gene flow throughout our history,
    Wrights FST 0.156.

Black bar represents humans compared to other
mammals, such as white tailed deer, gray wolves,
or Grants gazelle data from Templeton (1998,
2002.)
10
Estimate of gene flow between human
subpopulations
  • Wrights Fst for human data 0.156
  • We can calculate the effective population size
    and the migration rate for humans by the
    equation
  • Fst 1/(4Nm 1)
  • Thus Nm 1.35
  • Thus modern human genetic diversity can be
    explained by the long term average of 1.35
    individuals per 25 years, or 13.5 per 250 years,
    or 135 per 2,500 years.
  • Thus sporadic movements that over long periods of
    time that average out to these values could
    easily explain human genetic diversity.

Fig. 2.15.1, Cavalli-Sfroza, Menozzi, and Piazza
1994.
11
Isolation by distance
Humans best fit a gene flow, isolation by
distance model, Templeton, 2002. This means that
human populations that live closest to each
other, share the most genetic variation in common.
Figure 2.3 Templeton 2002
12
Human migration 101
  • Anatomically modern humans evolve in Africa gt
    160,000 ybp.
  • Some leave Africa sometime around 75,000 -
    55,000 ybp.
  • Replace Neanderthals in Europe and archaic humans
    around the world.
  • Arrive in Western hemisphere between 34,000 and
    18,000 ybp.
  • Multiple migrations in different pre-historic
    periods, followed by different migrations in
    historical periods.

13
Most genetic variation is shared between
geographically separated populations
14
Nucleotide similarities
  • Identical twins 10,000/10,000
  • Siblings 9,995/10,000
  • Unrelated individuals 9,990/10,000
  • Human/Chimp 9,900/10,000
  • Human/Flowering plant 6,700/10,000

However, with a genome estimated at 3 billion
base pairs, unrelated humans can be different at
3,000,000 base pairs.
15
Estimates of genetic distance are dependent upon
how they are calculated.
Methods that examine DNA directly reveal more
variation than can be seen at the protein level,
particularly if portions of the genome that are
not coded are included. Coding sequences
produce transfer RNAs, ribosomal RNAs, or
proteins, while non-coding sequences include
introns, regions that flank coding regions,
regulatory sites, and pseudogenes. In
Eukaryotes most of the genome is non-coding. For
example, it has been estimated that as much as
95 of human DNA is non-coding.
16
Non-coding DNA and ancestry
Genetic changes in introns and pseudogenes (often
called junk DNA), do not face selection and
therefore accumulate mutations freely. Thus,
non-coding segments are exceedingly useful for
establishing ancestry. This is because due to
chance historical events, populations can differ
in allele frequencies at these loci.
Fst data from Tischkoff and Kidd, 2004
17
Non-coding DNA and ancestry II
Rosenberg et al. Science 298, 2002 utilized an
algorithm called structure. They examined the
sequences of individuals from various populations
and Showed they could be clustered in a variety
of ways.
18
Non-coding DNA and ancestry III
Tischkoff and Kidd 2004, Least Squared tree for
37 populations, using 80 loci with 620 alleles.
The populations used are described in Allele
Frequency Database (ALFRED). However, ALFRED is
still very incomplete, missing suitable data on
many regions of the world, including North
Africa. In addition, the populations had
different characteristics, some were indigenous,
while others had greater amounts of admixture.
19
Within Population Distribution in the Genetically
Defined Clusters of Wilson et al. 2001.
Wilson et. al. in Nature Genetics, 29 265-69,
2001 using a panel of 39 microsatellite markers
showed that genetic variants of drug metabolizing
enzymes can be clustered into four
groups. However the four groups did not match
the common social definitions of race.

20
Actual membership in B Cluster
This is true because the population sizes are
different. Thus every genetically defined
cluster will have significant numbers of Chinese,
simply due to Chinas size. If other populations
are included, such as India, these figures would
shift again. Thus, we should expect all suitably
large populations to have people from all drug
metabolizing clusters.
21
Greater numbers of microsatellite markers (326)
were able to correlate self-identification with
genetic clustering.
Tang, et al. 2005 used Structure with K 2, 3, 4
or more clusters. When K 2, Chinese/Japanese
emerged as a group from all others, K 3, gives
African Am., Eu. Am. Mex. Am.,
Chinese/Japanese and K 4 is shown above.
22
Structuring non-coding genetic variation weakly
revealed candidate markers for hypertension.
Approximately 5 of the markers tested showed any
significant difference between normatensive and
hypertensive individuals. For the Chinese sample
it Was about 4.4, Mexican American 5.7, and
European American about 4.3. The paper did not
report whether the significant markers were
similar for all Populations tested.
23
Gene Flow Admixture
  • There is a wide variety of admixture percentages
    in North Americans with African descent.
  • Recent measures suggest that the average African
    Americans has on average 17 - 20 European
    admixture.
  • Also there could be as much as 10 American
    Indian admixture.
  • Therefore, could be as much as a 30 probability
    of African American genetic predisposition
    actually originated in Asians and Europeans.
  • Remember also that Asians and Europeans began
    their genetic odyssey in Africa, hence at any
    specific locus, a European or Asian may have an
    allele that was originally African, as opposed to
    one that originated outside of Africa.

Only 6 of the individuals in this study who
self-identified as African American had a
majority of their genetic markers
indicating African Origin this would differ by
region. However, 93 of self-identified European
Americans had the majority of their genetic
markers originating in Europe. Self identified
American Indians would show the African American
pattern and at present, self-identified Asian
Americans would show the European pattern, Sinha
et al. 2006, NEJM, 354(4) 421-22.
24
However, populations differ in specific coding
gene frequencies phenylketonuria mechanism,
mutation/selection balance or genetic drift.
Note, that while the Chinese and Japanese belong
to the same genetic cluster as determined by
SNPs, they differ in orders of magnitude in
phenylketonuria frequency and while Nigerians and
Icelanders are in different clusters they have
near identical frequencies of blood group O.
25
Summarized from Table 1, Tate and Goldstein,
Nature Genetics 2004
26
Summarized from Table 1, Tate and Goldstein,
Nature Genetics 2004
27
End Notes
28
The intellectual program of social dominance
  • The history of all hitherto existing society, is
    the history of individual and groups of males
    attempting to sub-ordinate other males and
    females (social dominance.)
  • Hierarchical society may have been fixed in our
    primate lineage Orangutans, Gorillas,
    Chimpanzees, and humans.
  • Found in all societies that produced a social
    surplus, such as Egyptian, Greek, Roman, Aztec,
    Chinese, Japanese, etc.
  • Intellectual programs were developed to justify
    some groups garnering more of the societys
    production than others. This ultimately
    translated into that groups greater material
    well-being, such as health, emotional
    satisfaction, and reproductive advantage.

29
Any genetic explanation of intelligence would
require that environments were equalized.
No such equality of environments exists or has
ever existed for minorities in America. Furthermo
re, this is impossible since by definition the
social environment of minorities must be
different from that of majorities. The
environments are made even more disparate by the
social dominance of the European population.
30
Affirmative action for the dominant population
  • The vast majority of federal and state government
    actions have differentially benefited people of
    European descent.
  • Consider the Indian Removal Act of 1830, the five
    civilized tribes were forced to give up the land
    that now comprises most of Tennessee, Georgia,
    Kentucky, and Mississippi.
  • They were forcibly moved west of the Mississippi
    River, 4,000 of 18,000 died during the trail of
    tears.
  • They were promised this land, as long as the
    waters run and the grasses grow. Well we know
    what happened to that promise.

31
Give me your huddled masses so long as they are
white.
  • US immigration policy was biased toward races
    that could be assimilated into America.
  • This meant in practice that 19th century
    immigration was to match the composition of the
    country in the 1824 census (mainly Anglo-Saxons,
    Irish, Swedes, Germans, and other northern
    Europeans.
  • After slave importation stopped, there was
    virtually no legal immigration of Africans or
    Afro-Caribbeans.
  • Congress passed the Chinese Exclusion Act in
    1880.
  • Japanese immigration to the US begins in earnest
    in the early 20th century.

32
Governmental action creates modern America,
leaves out non-whites
  • Housing act of 1949 makes homes affordable for
    the first time.
  • Between 1934 1962, FHA guarantees 120 billion
    dollars of home loans.
  • Less than 2 are made to non-whites.
  • The suburbs are born, housing values are
    determined by how white your neighborhood is.

33
Social dominance can increase risk of toxic
exposure.
Race/ethnicity, income, and home ownership (NJ,
2003.)
34
Social hierarchy harms those who are dominated
  • Neuroscience has begun to look at many genetic
    variants between individuals that correlate to
    behavior, such as addiction.
  • Cocaine addiction is linked to dopamine
    transporters, genetic variation exists in humans
    at these loci.

35
One type of such harm has been shown
experimentally in other primates
  • Social subordinate Macaques were more likely to
    self-administer cocaine (addiction.)
  • This was lower in monkeys housed alone or who
    were socially dominant.
  • African American college students who reported
    suffering racist harassment were twice as likely
    to use tobacco daily, Bennett et al. 2005, AJPH.

Morgan et. al. Nature Neuroscience, Vol. 5 No.
2, February 2002.
36
The impact of environmental differences is complex
  • Studies of malnutrition in rats showed that
    maternal effects on adult health extended over
    several generations.
  • We have already seen that differential stress
    exposure plays a role in predisposing some
    African Americans to hypertension.
  • Offspring of alcoholic mothers show FA in their
    teeth, FA has been linked to lower IQ in college
    students.
  • Numerous studies show that lasting adult
    pathology can result from stress in the maternal
    environment Desai et al. 1995 Hales et al.
    1996 Napoli et al. 1997 Waterland and Garza
    1999 Mustillo, S. et al. 2004 Collins et al.,
    2004.
  • Another recent study showed parental exposure to
    racial discrimination had negative impacts on the
    mental health of their pre-school aged children,
    Caughy et al. 2004.

37
Distribution of Sickle Cell Anemia Allele is
discordant with race.
  • Distributed at high frequency in Negroids and
    Caucasoids.
  • Seen as Black disease in U.S. due to
    importation of slaves derived from W. Africa.

38
Malaria in the USA
  • Did the presence of the allele help Blacks
    fight off malaria relative to Whites in North
    America?
  • In the early 20th century, an estimate of Blacks
    heterozygous for the sickle cell trait was about
    8.
  • Yet, in 10 southern states, Blacks suffered
    25/100,000 death rate v. only 7/100,000 for
    whites in 1921 1923 (who supposedly did not
    have the allele.)
  • Grover 1937, J. Negro Education (6), 281.

39
Genetic variation hypertension
  • A number of gene loci have been associated with
    increased risk of hypertension.
  • AGT -- which codes for angiotensinogen a protein
    made by the liver and circulates in excess
  • ACE angiotensin converting enzyme

40
Genetic variation hypertension II
  • At the angiotensinogen locus the 235T mutant has
    tyrosine switched for methionine.
  • In Euro-Americans, 235T is associated with an
    increased risk of hypertension.
  • The 235T allele is found at a frequency of 85 in
    African Americans.
  • However, 235T is not associated with increased
    hypertension risk in Nigerians.

Cooper, Rotimi, Ward 1999, pg. 42.
41
Genetic variation hypertension III
  • At the ACE locus there is a common alu insertion
    polymorphism that affects the activity of this
    enzyme.
  • The D allele is characterized by an absence of
    these alu insertions, and thus have higher
    enzymatic activity.
  • The available evidence shows that the enzymatic
    activity of II, ID, and DD genotypes are similar
    in Nigerians, Jamaicans, and in the United States
    (all populations.)
  • Hence the deletion genotypic doesnt seem to be
    influenced by racial background.
  • Source R.S. Cooper (1997).

42
Genetic variation and hypertension
  • There are at least 33 genetic systems with gt 63
    loci involved in hypertension predisposition.
  • In studies on hypertension published between 1997
    2003, only 2/10 found frequency differences in
    genetic variants in the direction of the proposed
    health differential.
  • In 8/10 studies, genetic variation existed, but
    it was not in the direction of the hypertension
    rates seen in America!

43
Hypertension III
  • Genetic variation in doesnt explain hypertension
    differentials
  • angiotensin converting enzyme
  • Angiotensinogen I and II
  • a- and b- adrenergic receptors
  • Plasma kallikrein
  • G protein-b3

44
b2-adrenergic polymorphisms The gly16 variant has
been associated with hypertension in
Afro-Caribbeans and Norwegians, but not African
or European Americans. The frequency of the
gly16 variant was slightly higher in European
Americans it was not significantly different
between the normal and hypertensive in either
group.
45
Hypertension?
  • Actually, when hypertension rates are stratified
    by socioeconomic status, the differential is
    located amongst African Americans in the higher
    categories.
  • This is means that the hypertension difference
    results from a biological response to
    social/cultural factors (e.g. control racism,
    reduce hypertension differential.)
  • Neser et al. 1986 Broman 1989 Calhoun 1992
    Light 1995.

46
Irrational resuscitation of race
  • Actually Wilson et al. examined population
    samples from around the world including
    Norwegians Ashkenazi Jews Armenians South
    China Papua, NG East and West Africa and
    Afro-Carribeans.
  • They found that 4/6 genetic variants they
    examined could be formed into four clusters.
  • This, of course means that 2/6 could not be
    clustered! (a fact not mentioned by Risch.)
  • Most importantly, Wilson et al. concluded that
    the four genetic clusters they discovered, did
    not match, socially constructed race or ethnicity
    (again a fact not mentioned by either Risch or
    Wade.)
  • Goldstein and Chkhi 2002 interpret Wilson et al.
    races in any meaningful sense of the term do not
    exist in the human species, An. Rev. Genomics
    and Human Genetics, vol. 3

47
Distribution of Sickle Cell Anemia Allele is
discordant with race.
  • The origin of the allele is uncertain.
  • However it is distributed at high frequency in
    Negroids and Caucasoids.
  • High altitude Kenyans dont have any sickle cell.
  • Seen as Black disease in U.S. due to
    importation of slaves derived from W. Africa were
    malaria was prevalent.

Fig. 5.8, Ridley 1996
48
Polymorphic loci vary in frequency
  • Polymorphic loci have numerous alleles, with no
    single allele at a frequency gt 99.
  • Phenylketonuria, q 0.01
  • Tay Sachs A, q 0.017
  • Cystic Fibrosis, q 0.022
  • Sickle Cell Anemia, q 0.050

Distribution of CF D F-508 allele, Fig. 2.14.10,
Cavalli-Sforza, Menozzi, and Piazza, 1994.
49
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