Genetic views on race

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Genetic views on race vary considerably between and within academic disciplines. Genetic views differ from historical ones. Many views are complex, and are distinguished by subtle differences. Often the significance of differences between views is related to the use of race in biomedicine. This article compares the major contemporary views on race.

Contents

[edit] Summary of contemporary views

Agreement/Disagreement of Cultural
and Physical Anthropologists with the statement that
"There are biological races in the species Homo sapiens"
1985 vs. 1999[1]
Cultural % Physical % Combined %
1985 1999 1985 1999 1995 1999
agree 30 14 50 24 39 18
neutral 17 6 10 7 14 7
disagree 53 80 40 69 47 75

[edit] Do human races exist?

[edit] What about subspecies/breed?

  • The terms 'race' and 'subspecies' are often used synonymously, some argue this is the correct definition (Kittles?).
  • Typically, 'race' is used for humans and 'subspecies' or 'breed' for non-humans.
  • When they are distinguished, 'race' is generally a lower level category than 'subspecies'.

[edit] If race had a biological basis, what would it be?

  • Taxonomic: "An aggregate of phenotypically similar populations of a species, inhabiting a geographic subdivision of the range of a species, and differing taxonomically from other populations of the species." (Mayr, 1969)
  • Population: "Races are genetically distinct Mendelian populations. They are neither individuals nor particular genotypes, they consist of individuals who differ genetically among themselves." (Dobzhansky, 1970)
  • Clines:
  • Lineage: "A [race] is a distinct evolutionary lineage within a species. This definition requires that a [race] be genetically differentiated due to barriers to genetic exchange that have persisted for long periods of time; that is, the [race] must have historical continuity in addition to current genetic differentiation." (Templeton, 1998)

[edit] The phylogeographic subspecies definition

A phylogeographic criteria for 'subspecies' was established in the early 1990s (Avise and Ball, 1990; O’Brien and Mayr, 1991).

"members of a subspecies would share a unique, geographic locale, a set of phylogenetically concordant phenotypic characters, and a unique natural history relative to other subdivisions of the species. Although subspecies are not reproductively isolated, they will normally be allopatric and exhibit recognizable phylogenetic partitioning. ... evidence for phylogenetic distinction must normally come from the concordant distributions of multiple, independent genetically based traits." (Miththapala et al., 1996)

[edit] Background

[edit] Total human genetic diversity

It is often claimed that human genetic diversity is smaller than that of other mammals.

[edit] Time frame of modern human evolution

Mitochondrial DNA from contemporary humans coalescences to a common ancestor living 150,000 years ago (see Mitochondrial Eve). However, nuclear DNA loci have a range of coalescence times, some predating the origin of modern humans or even hominids.

[edit] Distribution of genetic variation within/between populations

Some scientists have argued there exists more variation within racial groups than between, and therefore human races have no taxonomic value. This opinion can be traced back to a 1972 paper by Richard Lewontin. Some researchers report the variation between racial groups (measured by Sewall Wright's population structure statistic FST) accounts for as little as 5-7% of human genetic variation. This argument was widely popularized after Lewontin's original publication.

However, most geneticists now recognize that low FST values do not invalidate the suggestion that there might be different human races because of technical limitations of FST (Edwards, 2003), see Lewontin's Fallacy.

Populations within continents are more closely related to one another than to populations on other continents. Genetic variation between races is highly structured (Risch, 2002). Thus, when one considers many points (i.e., genetic loci) of variation one can distinguish groups and allocate people into groups (Bamshad, 2004).

[edit] Topical comparisons

[edit] Do biologically distinct races exist?

[edit] Genetic confirmation

According to Arthur Jensen the traditional races of physical anthropology have been more or less confirmed by the research of Cavalli-Sforza.

On pgs 430-431 of the g factor Jensen writes:

Cavalli-Sforza et al. transformed the distance matrix to a correlation matrix consisting of 861 correlation coefficients among the forty-two populations, so they could apply principal components (PC) analysis on their genetic data...PC analysis is a wholly objective mathematical procedure. It requires no decisions or judgments on anyone's part and yields identical results for everyone who does the calculations correctly...The important point is that if various populations were fairly homogenous in genetic composition, differing no more genetically than could be attributable only to random variation, a PC analysis would not be able to cluster the populations into a number of groups according to their genetic propinquity. In fact, a PC analysis shows that most of the forty-two populations fall very distinctly into the quadrents formed by using the first and second principal component as axes...They form quite widely separated clusters of the various populations that resemble the "classic" major racial groups-Caucasoids in the upper right, Negroids in the lower right, North East Asians in the upper left, and South East Asians (including South Chinese) and Pacific Islanders in the lower left...I have tried other objective methods of clustering on the same data (varimax rotation of the principal components, common factor analysis, and hierarchical cluster analysis). All of these types of analysis yield essentially the same picture and identify the same major racial groupings.

Image:Fig.2.3.542pop.jpg

Elsewhere in Jensen's writings, he equates North East Asians with mongoloids, which along with Caucasoids and Negroids, form what Jensen describes as the three broadest population groups. To test the reliability of these broadgroupings, Jensen performed his own independent varimax rotated principal component analysis described on paged 518 of the g factor:

I have used a somewhat different collection of only 26 populations from around the world that were studied by the population genetecists Nei & Roychoudhury (1993), whose article provides the genetic distance matrix among the 26 population samples, based on 29 polymorphic genes with 121 alleles...Note that some groups have major and minor loadings on different components, which represent not discrete categories, but central tendencies. The six rotated components can display clusters that can be identified as follows: (1) Mongoloids, (2) Caucasoids, (3) South Asians and Pacific Islanders, (4) Negroids, (5) North and South Amerindians and Eskimos, (6) aboriginal Australians and Papuan New Guineans. The genetic groupings are clearly similar to those obtained by Cavali-Sforza et al. using other methods applied to other samples.

Jensen is not alone in merging traditional racial lables like mongoloid and caucasoid with modern advances in genetics nor is he alone in separating Southeast Asians from the mongoloid race. According to The Human Species (2003) and Physical Anthropology, humanity can be divided into two major braches: the African branch and the non-African branch. The non-African branch includes two subgroups, one Eurasian and the other Oceanic. The Eurasian and Oceanic branches are the products of this common origin. The Eurasian branch split into the Caucasoid and Mongoloid branches. The Mongoloid branch then divided into the East Asian subgroup and the Amerindian subgroup. The Oceanic branch divided into the Southeast Asian subgroup and the Pacific Islander subgroup. According to The Human Species (2003), East Asians generally are more genetically similar to the South Asians than to Southeast Asians, because the Far East and the Indian Subcontinent are members of the Eurasian branch while Southeast Asians (including southern Chinese) are members or the Oceanic branch. More interestingly, Asians have very local genetic clusters inside these regions, implying different Asian ethnic groups have not historically intermarried with each other. Examples of localized genetic clusters include Japan, Korea, Mongolia and China which form separate genetic clusters from each other.[2][3]


The following chart by Cavalli-Sforza shows the genetic distance between the major races that Jensen describes and the separate branches they sit on:

Image:DNAtree.gif

However Cavalli-Sforza publicly avoids agreeing with Jensen's interpretation of his work stating, "The classification into races has proved to be a futile exercise." Additionally, according to an article published in The Economist, the work of Cavalli-Sforza "challenges the assumption that there are significant genetic differences between human races, and indeed, the idea that 'race' has any useful biological meaning at all." [3] (The Human Genome Survey, 1 July 2000, pg. 11) "Don't believe any of this" explains Amazon.com reviewer Steve Sailer. "This is merely a politically correct smoke screen that Cavalli-Sforza regularly pumps out that keeps his life's work -- identifying the myriad races of mankind and compiling their genealogies -- from being defunded by the commissars of acceptable thinking at Stanford.

What's striking is how the press falls for his squid ink, even though Cavalli-Sforza can't resist proudly putting his genetic map showing the main races of mankind right on the cover of his 1994 magnum opus, "The History and Geography of Human Genes."[4]

Denying the existence of race remains popular:"Indeed, there is no distinctive biological reality called 'race' that can be determined by objective scientific procedures. The soical, medical, and physical sciences have demonstrated this fact."(Racial and Ethnic Relations, page 5)[5] Leading geneticist Richard Lewontin states "every human genome differs from every other", showing the impossibility of using genetics to define races. (Biology as Ideology, page 68).[6]


Ongoing debate exists over the merit of the concept of 'race', especially from the perspective of genetics. Many scientists argue that common racial classifications are insufficient, inaccurate, or biologically meaningless.[7] For example, Lewontin (1972) argues that there is no biological basis for race on the basis of research indicating that more genetic variation exists within such races than between them. However, some geneticists have claimed that many of these "well-intentioned"[8] statements are false and do not "derive from an objective scientific perspective."[9] They argue instead "that from both an objective and scientific (genetic and epidemiologic) perspective there is great validity in racial/ethnic self-categorizations, both from the research and public policy points of view."[9] It is well known that many alleles vary in frequency across human populations.

[edit] Do self-identified races have biological validity?

Opinions vary. Recent research indicates that self-described race is a near-perfect indicator of an individual's genetic profile, at least in the United States. Using 326 genetic markers, Tang et al. (2005) identified 4 genetic clusters among 3,636 individuals sampled from 15 locations in the United States, and were able to correctly assign individuals to groups that correspond with their self-described race (white, African American, East Asian, or Hispanic) for all but 5 individuals (an error rate of 0.14%). They conclude that ancient ancestry, which correlates tightly with self-described race, and not current residence, is the major determinant of genetic structure in the US population. Others claim self-identified races do not correspond to biology. The "difficulty with the biosocial approach is that in the everyday world, racial and ethnic relations are immediately social rather than biological... Biologically diverse Italian immigrants from different regions of Italy gained a sence of being Italian American (even Italian) in the United States." (Racial and Ethnic Relations, page 32)[10]

[edit] References

  1. ^ Bindon, Jim. University of Alabama. "Post World War II". 2005. August 28, 2006.
  2. ^ John Relethford, The Human Species: An introduction to Biological Anthropology, 5th ed. (New York: McGraw-Hill, 2003). - +
  3. ^ Philip L. Stein and Bruce M. Rowe, Physical Anthropology, 8th ed. (McGraw-Hill, 1996)
  4. ^ [[1]]
  5. ^ Feagin, Joe R. Racial and Ethnic Relations. United States of America:Prentice Hall,2003.
  6. ^ Lewontin, R.C. Biology as Ideology The Doctrine of DNA. Ontario:HarperPerennial, 1991.
  7. ^ Smedley and Smedley 2005; Helms et al. 2005; [2]
  8. ^ Collins 2004
  9. ^ a b Risch et al. 2002
  10. ^ Feagin, Joe R. Racial and Ethnic Relations. United States of America:Prentice Hall,2003.
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