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AW: AW: Biology teachers  Bruce Jackson
 May 22, 2007 19:04 PDT 

 -----Ursprüngliche Nachricht-----
Von: Peter Staudenmaier [mailto:pst-@hotmail.com]
Bruce writes:


 
 By the
way,
"Europeans" are not a population in evolutionary terms. Greetings,

I did realise that!


But you forgot about it while writing your previous posts on blood type
and
race? Slipped your mind momentarily?

Variety ist he spice of life!

 

 But then what is a population? (in evolutionary terms)?


One that is subject to a relevantly similar set of selection pressures and
thus shows a shift in genetic composition over time. That is one obvious
reason why human 'races' are not biological units. Could you please,
pretty
please, take a look at any of the sources I've provided? They're just a
click away. You could start with this one from geneticist Richard
Lewontin:

http://raceandgenomics.ssrc.org/Lewontin/


Since you seem reluctant to follow links, here's the full text:

I'm not reluctant to follow links at all: I'm a humble waldorf teacher with,
especially at this time of year, very little time to follow up hundreds of
suggested sources: I DO appreciate that you mean well, Peter! Maybe one day
we really will meet? Then you can tell me face to face and I needn't go off
following links. We have a great school café that's open morning and indeed
until 15 Uhr most days.

 

Confusions About Human Races

By R.C. Lewontin

Over the last thirty five years a major change has taken place in our
biological understanding of the concept of human “race,” largely as a
consequence of an immense increase in our knowledge of human genetics. As
a
biological rather than a social construct, “race” has ceased to be seen as
a
fundamental reality characterizing the human species. Nevertheless, there
appear from time to time claims that racial categories represent not
arbitrary socially and historically defined groups but objective
biological
divisions based on genetic differences. The most recent widely noticed
rebirth of such claims is an essay by Armand Marie Leroi on the Op-Ed page
of The New York Times (March 14, 2005), an essay that illustrates both the
classical confusions about the reality of racial categories and the more
recent erroneous conclusions about the relevance of such racial
identifications for medical practice.

There are four facts about human variation upon which there is universal
agreement. First, the human species as a whole has immense genetic
variation
from individual to individual. Any two unrelated human beings differ by
about 3 million distinct DNA variants.

Second, by far the largest amount of that variation, about 85%, is among
individuals within local national or linguistic populations, within the
French, within the Kikuyu, within the Japanese. There is diversity from
population to population in how much genetic variation each contains,
depending upon how much immigration into the population has occurred from
a
variety of other groups and also on the size of the population. The United
States, with a very large population whose ancestors came from all over
the
earth including the original inhabitants of the New World, is genetically
very variable whereas small populations of local Amazonian tribes are less
genetically variable, although they are by no means genetically uniform.
Despite the differences in amount of genetic variation within local
populations, the finding that on the average 85% of all human genetic
variation is within local populations has been a remarkably consistent
result of independent studies carried out over twenty-five years using
data
from both proteins and DNA.

Of the remaining 15% of human variation, between a quarter and a half is
between local populations within classically defined human “races,”
between
the French and the Ukrainians, between the Kikuyu and the Ewe, between the
Japanese and the Koreans. The remaining variation, about 6% to 10% of the
total human variation is between the classically defined geographical
races
that we think of in an everyday sense as identified by skin color, hair
form, and nose shape. This imprecision in assigning the proportion of
variation assigned to differences among population within ”races” as
compared to variation among “races,” arises precisely because there is no
objective way to assign the various human populations to clear-cut races.
Into which “race” do the Hindi and Urdu speakers of the Indian sub-
continent
fall? Should they be grouped with Europeans or with Asians or should a
separate race be assigned to them? Are the Lapps of Finland and the Hazari
of Afghanistan really Europeans or Asians? What about Indonesians and
Melanesians? Different biologists have made different assignments and the
number of “races” assigned by anthropologists and geneticists has varied
from 3 to 30.

Third, a small number of genetic traits, such as skin color, hair form,
nose
shape (traits for which the genes have not actually been identified) and a
relatively few proteins like the Rh blood type, vary together so that many
populations with very dark skin color will also have dark tightly curled
hair, broad noses and a high frequency of the Rh blood type R0. Those who,
like Leroi, argue for the objective reality of racial divisions claim that
when such covariation is taken into account, clear-cut racial divisions
will
appear and that these divisions will correspond largely to the classical
division of the world into Whites, Blacks, Yellows, Reds and Browns. It is
indeed possible to combine the information from covarying traits into
weighted averages that take account of the traits' covariation
(technically
known as "principal components" of variation). When this has been done,
however, the results have not borne out the claims for racial divisions.
The
geographical maps of principal component values constructed by Cavalli,
Menozzi and Piazza in their famous The History and Geography of Human
Genes
show continuous variation over the whole world with no sharp boundaries
and
with no greater similarity occurring between Western and Eastern Europeans
than between Europeans and Africans! Thus, the classically defined races
do
not appear from an unprejudiced description of human variation. Only the
Australian Aborigines appear as a unique group.

A clustering of populations that does correspond to classical continental
"races" can be acheived by using a special class of non-functional DNA,
microsatellites. By selecting among microsatellites, it is possible to
find
a set that will cluster together African populations, European
populations,
and Asian populations, etc. These selected microsatellite DNA markers are
not typical of genes, however, but have been chosen precisely because they
are "maximally informative" about group differences. Thus, they tell us
what
we already knew about the differences between populations of the classical
"races" from skin color, face shape, and hair form. They have the added
advantage of allowing us to make good estimates of the amount of
intermixture that has occurred between populations as a result of
migrations
and conquests.

The every-day socially defined geographical races do identify groups of
populations that are somewhat more closely similar to each other
genetically. Most important from the standpoint of the biological meaning
of
these racial categories, however, most human genetic variation does not
show
such "race" clustering. For the vast majority of human genetic variations,
classical racial categories as defined by a combination of geography, skin
color, nose and hair shape, an occasional blood type or selected
microsatellites make no useful prediction of genetic differences. This
failure of the clustering of local populations into biologically
meaningful
"races" based on a few clear genetic differences is not confined to the
human species. Zoologists long ago gave up the category of "race" for
dividing up groups of animal populations within a species, because so many
of these races turned out to be based on only one or two genes so that two
animals born in the same litter could belong to different "races."

In his article, Leroi is inconsistent and shifting in his notion of race.
Sometimes it corresponds to the classical social definitions of major
races,
but elsewhere he makes “race” coincident with a small local group such as
the Negritos or Inuit. In this shifting concept of “race” he goes back to
the varying use of the term in the 19th century. Then people spoke of the
“Scots race,” “the Irish race” and the “race of Englishmen.” Indeed “race”
could stand for a family group defined by male inheritance, as in the
description of the last male in a family line as “the last of his race.”
This inconsistent usage arises from the fact that there is no clear
criterion of how much difference between groups of genetically related
individuals should correspond to the category “race.” If it had turned out
that groups of related populations were clearly different in the great
majority of their genes from other groups, then racial categories would be
clear and unambiguous and they would have great predictive power for as
yet
unstudied characters. But that is not the way it has turned out, at least
for the human species.

The fourth and last fact about genetic differences between groups is that
these differences are in the process of breaking down because of the very
large amount of migration and intergroup mating that was always true
episodically in the history of the human species but is now more
widespread
than ever. The result is that individuals identified by themselves or
others
as belonging to one “race,” based on the small number of visible
characters
used in classical race definitions, are likely to have ancestry that is a
mixture of these groups, a fact that has considerable significance for the
medical uses of race identification.

A common claim, repeated by Leroi, is that racial categories are of
considerable medical use, especially in diagnostic testing because some
genetic disorders are very common in ancestral racial populations. For
example sickle cell anemia is common among West Africans, who were brought
as slaves to the New World, and Tay-Sachs disease is common among
Ashkenazi
Jews. So, it is argued, racial information can be a useful diagnostic
indicator. Certainly classical “race” contains some medically relevant
information in some cases, as for example “white” as opposed to “African
American” if the contrast is between Finland and West Africa, but not if
it
is a contrast between a “white” Mediterranean and an “Asian” Indian. There
is a confusion here between race and ancestry. Sickle cell anemia is in
high
frequency not only in West Africans but also in some “white” Middle
Eastern
and Indian populations. Moreover, a person with, say, one African
great-grandparent, but who is identified by herself and others as “white”
has a one in eight chance of inheriting a sickle-cell mutation carried by
that ancestor. There are, in addition, a number of other simply inherited
hemoglobin abnormalities, the thalassemias, that are in high frequency in
some places in the Mediterranean (Sardinia), Arabia and southeast Asia.
The
highest frequency known for a thalassemia (80%) is in Nepal, but it is
rare
in most of Asia. The categorization of individuals simply as “white” or
“Afro-American” or “Asian” will result in a failure to test for such
abnormal hemoglobins because these abnormalities do not characterize the
identified “race” of the patient. Even group identities below the level of
the conventional races are misleading. Two of my incontrovertibly WASP
grandchildren have a single Ashenazi Jewish great-grandparent and so have
a
one in eight chance of inheriting a Tay-Sachs abnormality carried by that
ancestor. For purposes of medical testing we do not want to know whether a
person is “Hispanic” but rather whether that person’s family came from a
Caribbean country such as Cuba, that had a large influx of West African
slaves, or one in which there was a great deal of intermixture with native
American tribes as in Chile and Mexico, or one in which there was only a
negligible population of non-Europeans. Racial identification simply does
not do the work needed. What we ought to ask on medical questionnaires is
not racial identification, but ancestry. “Do you know of any ancestors who
were (Ashkenazi Jews, or from West Africa, from certain regions of the
Mediterranean, from Japan)?” Once again, racial categorization is a bad
predictor of biology.

There has been an interesting dialectic between the notion of human races
and the use of race as a general biological category. Historically, the
concept of race was imported into biology, and not only the biology of the
human species, from social practice. The consciousness that human beings
come in distinct varieties led, in the history of biology, to the
construction of “race” as a subgrouping within species. For a long time
the
category “race” was a standard taxonomic level. But the use of “race” in a
general biological context then reinforced its application to humans.
After
all, lots of animal and plant species are divided into races, so why not
Homo sapiens? Yet the classification of animal and plant species into
named
races was at all times an ill-defined and idiosyncratic practice. There
was
no clear criterion of what constituted a race of animals or plants that
could be applied over species in general. The growing realization in the
middle of the twentieth century that most species had some genetic
differentiation from local population to local population led finally to
the
abandonment in biology of any hope that a uniform criterion of race could
be
constructed. Yet biologists were loathe to abandon the idea of race
entirely. In an attempt to hold on to the concept while make it objective
and generalizable, Th. Dobzhansky, the leading biologist in the study of
the
genetics of natural populations, introduced the “geographical race,” which
he defined as any population that differed genetically in any way from any
other population of the species. But as genetics developed and it became
possible to characterize the genetic differences between individuals and
populations it became apparent, that every population of every species in
fact differs genetically to some degree from every other population. Thus,
every population is a separate “geographic race” and it was realized that
nothing was added by the racial category. The consequence of this
realization was the abandonment of “race” as a biological category during
the last quarter of the twentieth century, an abandonment that spread into
anthropology and human biology. However, that abandonment was never
complete
in the case of the human species. There has been a constant pressure from
social and political practice and the coincidence of racial, cultural and
social class divisions reinforcing the social reality of race, to maintain
“race” as a human classification. If it were admitted that the category of
“race” is a purely social construct, however, it would have a weakened
legitimacy. Thus, there have been repeated attempts to reassert the
objective biological reality of human racial categories despite the
evidence
to the contrary.

Interesting: the opening paragraph is most interesting - the research is
mostly from the last 30 years! When did Steiner die?


 

I also recommend these discussions of the same issue:


http://raceandgenomics.ssrc.org/Graves/


http://raceandgenomics.ssrc.org/Stevens/


http://raceandgenomics.ssrc.org/Goodman/


http://raceandgenomics.ssrc.org/Marks/


http://raceandgenomics.ssrc.org/Hubbard/
OK: but I don't really doubt the current definitions of race, and I'm not so
sure that they are relevant!

I'm re-writing all the posts that I'd written and posting them to topica and
yahoo - topica may eventually spew them out, but I frankly have given up!!

Bruce
	
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