posted 20 June 2005 02:18 PM            

S O Y Keita, R A Kittles1, et. al National Human Genome Center, College of Medicine, Howard University, Washington, DC 20060, USA.
Department of Anthropology, Smithsonian Institution, Washington, DC, USA.
Department of Molecular Virology, Immunology, and Medical Genetics, The Ohio State University, Columbus, Ohio 43210, USA.

'Race': semantics and confusion

The term 'race' engenders much discussion, with little agreement between those who claim that 'races' are real (meaning natural) biological entities and those who maintain that they are socially constructed1.

The former group sometimes stresses empirical evidence for the existence of biological 'racial' differences, and the latter stresses the role that human agency has had in creating distinctions between people (on any level).

Biologists also disagree about the meaning of 'race', and whether it is applicable to human infraspecific (within-species) variation2, 3, 4, 5.

An examination of these discussions indicates that there is a problem with semantics. 'Race' is not being defined or used consistently; its referents are varied and shift depending on context. The term is often used colloquially to refer to a range of human groupings. Religious, cultural, social, national, ethnic, linguistic, genetic, geographical and anatomical groups have been and sometimes still are called 'races'6, 7. In anthropology, the meaning of race became formalized for humans and restricted to units based on biological variation in keeping with general zoological practice8, 9. Classifications were based on somatic traits.

'Race' is applied in formal taxonomy to variation below the species level. In traditional approaches, substantively morphologically distinct populations or collections of populations occupying a section of a species range are called subspecies and given a three-part Latin name10. In current systematic practice, the designation 'subspecies' is used to indicate an objective degree of microevolutionary divergence11. Do any of the human groups called 'races', including those from traditional anthropology, meet this latter criterion?

We argue that the correct use of the term 'race' is the most current taxonomic one, because it has been formalized.

'Race' gains its force from its natural science root. The term denotes 'natural' distinctions and connotes differences not susceptible to change. One is led to ask, therefore, whether everything that is called a 'racial' difference is actually natural. 'Racial' differences carry a different weight than cultural differences. In terms of taxonomic precision and best practice, is it scientifically correct to identify European Americans, Asians and Pacific Islanders, Han Chinese, Hispanics and African Americans of Middle Passage descent as different races?

Although individuals may refer to themselves as belonging to a particular 'race', it is doubtful that this has been done with knowledge of, or concern for, zoological taxonomy, because the common use of the term has come from sociopolitical discourse. Individuals learned the 'race' to which they were assigned.

Although 'race' and subspecies are usually treated as equivalent, some zoological taxonomists reserve the word 'race' for local breeding populations, with subspecies being geographical collections of populations that are similar or the same in the defining traits. This causes no serious problem to this discussion, because the most commonly known anthropological classification of humans is said to consist of races.

If 'Caucasoid' is a subspecies, however, then an endogamous village population or ethnic group becomes a 'race'. This illustrates an inconsistency even in biological usage not found in scientific or sociopolitical practice: for example, how often are the Old Order Amish referred to as a 'race' in recent scientific literature? This group of people is a breeding population, based on a particular behavioral pattern of mate choice, as opposed to being defined by an anatomical trait complex.

'Race' and subspecies
Although the subspecies level is formally recognized in taxonomy, it has been criticized. Subspecies were primarily delimited by differences in selected observable morphological traits within a restricted geographical range. In practice, divisions were made based on a few prominent traits, with subsequent variation interpreted in terms of established units.

In the 1950s many zoological taxonomists became dissatisfied with the subspecies as a way to understand variation10, 12, 13. Criticisms included (i) the nonconcordance of traits, which made it possible to produce different classifications using the same individuals; (ii) the existence of polytopic populations, which are the product of parallel evolution; (iii) the existence of true breeding populations (demes) within previously delimited subspecies; and (iv) the arbitrariness of criteria used to recognized subspecies10. In addition, some traits were found to be clinally distributed, making the creation of divisions arbitrary.

Current systematic theory emphasizes that taxonomy at all levels should reflect evolutionary relationships.

For instance, the term 'Negro' was once a racial designation for numerous groups in tropical Africa and Pacific Oceania (Melanesians). These groups share a broadly similar external phenotype; this classification illustrates 'race' as type, defined by anatomical complexes. Although the actual relationship between African 'Negroes' and Oceanic 'Negroes' was sometimes questioned, these groups were placed in the same taxon. Molecular and genetic studies later showed that the Oceanic 'Negroes' were more closely related to mainland Asians.

Molecular systematics makes it possible to explore infraspecific variation to detect patterns that would reflect phylogenetic substructuring. Avise and Ball suggest a definition of 'subspecies' that is consistent with the goals of evolutionary taxonomy11: "Subspecies are groups of actually or potentially interbreeding populations phylogenetically distinguishable from, but reproductively compatible with, other such groups. Importantly the evidence for phylogenetic distinction must normally come from the concordant distributions of multiple, independent, genetically based traits."

This definition is different from the previous one in that it emphasizes phylogenetics. It is, in theory, more objective and consistent with neodarwinian evolutionary theory and can be used as the basis for determining whether or not modern Homo sapiens can be structured into populations divergent enough to be called 'races'. We know that there is human geographical variation, but does this infraspecific diversity reach a threshold that merits the designation 'subspecies', as is true with chimpanzees1?

'Race' and social construction
'Race' is 'socially constructed' when the word is incorrectly used as the covering term for social or demographic groups. Broadly designated groups, such as 'Hispanic' or 'European American' do not meet the classical or phylogenetic criteria for subspecies or the criterion for a breeding population. Furthermore, some of the 'racial' taxa of earlier European science used by law and politics were converted into social identities2.

For example, the self-defined identities of enslaved Africans were replaced with the singular 'Negro' or 'black', and Europeans became 'Caucasian', thus creating identities based on physical traits rather than on history and cultural tradition. Another example of social construction is seen in the laws of various countries that assigned 'race' (actually social group or position) based on the proportion of particular ancestries held by an individual. The entities resulting from these political machinations have nothing to do with the substructuring of the species by evolutionary mechanisms.

Human races as human variation
Arguments against the existence of human races (the taxa 'Mongoloid', 'Caucasoid' and 'Negroid' and those from other classifications) include those stated for subspecies and several others. The within- to between-group variation is very high for genetic polymorphisms (85%; refs. 16,17). This means that individuals from one 'race' may be overall more similar to individuals in one of the other 'races' than to other individuals in the same 'race'. This observation is perhaps insufficient, although it still is convincing because it illustrates the lack of a boundary.

Coalescence times, calculated from various genes suggest that the differentiation of modern humans began in Africa in populations whose morphological traits are unknown; it cannot be assumed from an evolutionary perspective that the traits used to define 'races' emerged simultaneously with this divergence. There was no demonstrable 'racial' divergence.

Y-chromosome and mitochondrial DNA genealogies are especially interesting because they demonstrate the lack of concordance of lineages with morphology and facilitate a phylogenetic analysis.

Individuals with the same morphology do not necessarily cluster with each other by lineage, and a given lineage does not include only individuals with the same trait complex (or 'racial type').

Y-chromosome DNA from Africa alone suffices to make this point.

Africa contains populations whose members have a range of external phenotypes. This variation has usually been described in terms of 'race' (Caucasoids, Pygmoids, Congoids, Khoisanoids).

But the Y-chromosome clade defined by the PN2 transition (PN2/M35, PN2/M2) shatters the boundaries of phenotypically defined races and true breeding populations across a great geographical expanse. African peoples with a range of skin colors, hair forms and physiognomies have substantial percentages of males whose Y chromosomes form closely related clades with each other, but not with others who are phenotypically similar.

The individuals in the morphologically or geographically defined 'races' are not characterized by 'private' distinct lineages restricted to each of them.

Human genome variation, demographic groups and disease

'Race' is a legitimate taxonomic concept that works for chimpanzees but does not apply to humans (at this time).

The nonexistence of 'races' or subspecies in modern humans does not preclude substantial genetic variation that may be localized to regions or populations. More than 10 million single-nucleotide polymorphisms (SNPs) probably exist in the human genome.

More than 5 million of these SNPs are expected to be common (minor allele frequency >10%)23. Most of these SNPs vary in frequency across human populations, and a large fraction of them are private or common in only a single population. Other genetic variants are also asymmetrically distributed.

This makes forensic distinctions possible even within restricted regions such as Scandinavia. Anonymous human DNA samples will structure into groups that correspond to the divisions of the sampled populations or regions when large numbers of genetic markers are used. This has been demonstrated with autosomal microsatellites, which are the most rapidly evolving genetic variants.

The DNA of an unknown individual from one of the sampled populations would probably be correctly linked to a population.

Because this identification is possible does not mean that there is a level of differentiation equal to 'races'.

The genetics of Homo sapiens shows gradients of differentiation.

'Race' and research
Modern human genetic variation does not structure into phylogenetic subspecies (geographical 'races'), nor do the taxa from the most common racial classifications of classical anthropology qualify as 'races'.

posted 21 June 2005 07:48 AM            

This thread should have been called "A lesson in Afrocentric propaganda".

posted 21 June 2005 08:53 AM            

No surprise at all.

Races really have no meaning biologically, and certainly not genetically.

Classification of humans into races has proven a futile excercise - S. Wells C. Cforza

Keep trying....

posted 22 June 2005 09:00 AM            

Genes, peoples, and languages L. Luca Cavalli-Sforza

About 8,000 years ago, a more advanced people, migrated to Europe bringing with them a new Y chromosome pattern [African E, West Asian J] and a new way of life: agriculture.

About 20 percent of Europeans now have the Y chromosome pattern from this migration, he said. - Peter Underhill, First Europeans.

we have evidence of the intrusion of peoples from northeast Africa to southwest Asia, the Y chromosome markers FADE OUT as you go deeper into Eurasia - Christopher Ehret