Race

The term race distinguishes a population of humans (or non-humans) from other populations. The most widely used human racial categories are based on visible traits (especially skin color and facial features), genes, and self-identification. Conceptions of race, as well as specific racial groupings, vary by culture and over time and are often controversial, for scientific reasons as well as their impact on social identity and identity politics. Legal definitions, common usage, and scientific meaning can all be conflated, causing confusion and controversy.

Since the 1940s, evolutionary scientists have rejected the view of race according to which a number of finite lists of essential characteristics could be used to determine a like number of races. Many evolutionary and social scientists think common race definitions, or any race definitions pertaining to humans, lack taxonomic rigour and validity. They argue that race definitions are imprecise, arbitrary, derived from custom, and that the races observed vary according to the culture examined. They further maintain that "race" as such is best understood as a social construct, and conceptualize and analyze human genotypic and phenotypic variation in terms of populations and clines instead. Some scientists, however, have argued that this position is motivated more by political than scientific reasons.

Since the 1990s, data and models from genomics and cladistics have resulted in a revolution in our understanding of human evolution, which has led some to propose a new "lineage" definition of race. These scientists have made related arguments that splitting humanity into separate races is valid when they are understood as fuzzy sets, clusters, or extended families.

Current disagreement across disciplines
One result of debates over the meaning and validity of the concept "race" is that the current literature across different disciplines regarding human variation lacks consensus, though some fields, such as biology, have strong consensus. Some studies use the word race in its previously essentialist taxonomic sense. Many still use the term race, but use it to mean a population, clade, or haplogroup. Others eschew the word race altogether, and use the word population as a less pejorative synonym.

In the 19th century, race was a central concept of anthropology. In 1866, James Hunt, the founder of the Anthropological Society of London, declared that anthropology’s primary truth “is the existence of well-marked psychological and moral distinctions in the different races of men.” However, this view became marginalised in the 20th century. Since 1932, college textbooks introducing physical anthropology have increasingly come to reject race as a valid concept: from 1932 to 1976, only seven out of thirty-two rejected race; from 1975 to 1984, thirteen out of thirty-three rejected race; from 1985 to 1993, thirteen out of nineteen rejected race. The American Anthropological Association, drawing on biological research, currently holds that "The concept of race is a social and cultural construction. . . . Race simply cannot be tested or proven scientifically," and that, "It is clear that human populations are not unambiguous, clearly demarcated, biologically distinct groups. The concept of 'race' has no validity . . . in the human species" (see [.) Nevertheless, many scientists, including some anthropologists, reject this position.

A 1985 survey (Lieberman et al. 1992) asked 1,200 scientists how many disagree with the following proposition: "There are biological races in the species Homo sapiens." The responses were: The figure for physical anthropologists at PhD granting departments was slightly higher, rising from 41% to 42%, with 50% agreeing. This survey, however, did not specify any particular definition of race; it is impossible to say whether those who supported the statement thought of race in taxonomic or population terms.
 * biologists 16%
 * developmental psychologists 36%
 * physical anthropologists 41%
 * cultural anthropologists 53%

History of the term
Given visual complex social relationships, humans presumably have always observed and speculated about the physical differences among individuals and groups. But different societies have attributed markedly different meanings to these distinctions. The division of humanity into distinct "races" can be traced as far back as the Ancient Egyptian sacred text the Book of Gates, which identifies four categories that are now conventionally labelled "Egyptians", "Asiatics", "Libyans", and "Nubians". However, such distinctions tended to merge differences defined by features such as skin color, with tribal and national identity. Classical civilizations from Rome to China tended to invest much more importance in family or tribal affiliations than in physical appearance (Dikötter 1992; Goldenberg 2003). Ancient Greek and Roman authors also attempted to explain and categorize visible biological differences between peoples known to them. Such categories often also included fantastical human-like beings that were supposed to exist in far-away lands. Some Roman writers adhered to an environmental determinism in which climate could affect the appearance and character of groups (Isaac 2004). But in many ancient civilizations, individuals with widely varying physical appearances could become full members of a society by growing up within that society or by adopting the society's cultural norms (Snowden 1983; Lewis 1990). Medieval models of race mixed Classical ideas with the notion that humanity as a whole was descended from Shem, Ham and Japheth, the three sons of Noah, producing distinct Semitic (Asian), Hamitic (African), and Japhetic (European) peoples.

At the end of the Reconquista, the Spanish Inquisition persecuted Jews and Muslims, theorizing a limpieza de sangre ("Cleanliness of blood") doctrine. Furthermore, after the discovery of the New World, Bartolomé de Las Casas opposed the conquistadores theories, upheld by Sepúlveda, on the pretended Amerindians's absence of souls.

It wasn't until the 16th century that the word race entered the English language, from the French race - "race, breed, lineage" (which in turn was probably a loan from Italian razza). Meanings of the term in the 16th century included "wines with a characteristic flavour", "people with common occupation", and "generation". The meaning "tribe" or "nation" emerged in the 17th century. The modern meaning, "one of the major divisions of mankind", dates to the late 18th century, but it never became exclusive (cf. continued use of "the human race"). The ultimate origin of the word is unknown; suggestions include Arabic ra'is meaning "head", but also "beginning" or "origin".

In Society Must be Defended (1978-79), Michel Foucault traced the "historical and political discourse" of "race struggle" to the 1688 "Glorious Revolution" in England and Louis XIV's reign in France, during which conflicting political values were ascribed to ancestral ethnicities (Saxon, Norman, Frankish etc). According to him, these debates initated a form of "popular history" based on ethnic identity, as opposed to the classical juridical and philosophical discourse of sovereignty. In England, it was used by Edward Coke and John Lilburne against the monarchy. In France, Boulainvilliers, Nicolas Fréret, and then Sieyès, Augustin Thierry and Cournot reappropriated this discourse. At the end of the 19th century, the notion of "race" was, according to Foucault, incorporated by racists biologists and eugenicists, who gave it the modern sense of "biological race", which was then be integrated to "state racism". Marxists also seized this historical and political discourse, transforming the essentialist biological notion of "race" into the concept of "class struggle."

The English word "race", along with many of the ideas now associated with the term, were products of the European era of exploration (Smedley 1999). As Europeans encountered people from different parts of the world, they speculated about the physical, social, and cultural differences between human groups. The rise of the African slave trade, which gradually displaced an earlier trade in slaves from throughout the world, created a further incentive to categorize human groups to justify the barbarous treatment of African slaves (Meltzer 1993). Drawing on classical sources and on their own internal interactions &mdash; for example, the hostility between the English and Irish was a powerful influence on early thinking about the differences between people (Takaki 1993) &mdash; Europeans began to sort themselves and others into groups associated with physical appearance and with deeply ingrained behaviors and capacities. A set of "folk beliefs" took hold that linked inherited physical differences between groups to inherited intellectual, behavioral, and moral qualities (Banton 1977). Although similar ideas can be found in other cultures (Lewis 1990; Dikötter 1992), they appear not to have had as much influence on social structures as they did in Europe and the parts of the world colonized by Europeans. However, often brutal conflicts between ethnic groups have existed throughout history and across the world, and racial prejudice against Africans also exists in non-colonised countries such as Japan and China. 

History of race research
See From "racial theory" to "racism"

The first scientific attempts to categorize race date from the 17th century, along with the development of European imperialism and colonization around the world. The first post-Classical published classification of humans into distinct races seems to be François Bernier's Nouvelle division de la terre par les différents espèces ou races qui l'habitent ("New division of Earth by the different species or races which inhabit it"), published in 1684.

17th and 18th century
In the 18th century, the differences between human groups became a focus of scientific investigation (Todorov 1993). Initially, scholars focused on cataloging and describing "The Natural Varieties of Mankind," as Johann Friedrich Blumenbach entitled his 1775 text (which established the five major divisions of humans still reflected in some racial classifications). From the 17th through the 19th centuries, the merging of folk beliefs about group differences with scientific explanations of those differences produced what one scholar has called an "ideology of race" (Smedley 1999). According to this ideology, races are primordial, natural, enduring, and distinct. Some groups might be the result of mixture between formerly distinct populations, but careful study can distinguish the ancestral races that had combined to produce admixed groups.

19th century
The 19th century saw attempts to change race from a taxonomic to a biological concept. In the 19th century a number of natural scientists wrote on race: Georges Cuvier, Charles Darwin, Alfred Wallace, Francis Galton, James Cowles Pritchard, Louis Agassiz, Charles Pickering, and Johann Friedrich Blumenbach. As the science of anthropology took shape in the 19th century, European and American scientists increasingly sought explanations for the behavioral and cultural differences they attributed to groups (Stanton 1960). For example, using anthropometrics, invented by Francis Galton and Alphonse Bertillon, they measured the shapes and sizes of skulls and related the results to group differences in intelligence or other attributes (Lieberman 2001).

These scientists made three claims about race: first, that races are objective, naturally occurring divisions of humanity; second, that there is a strong relationship between biological races and other human phenomena (such as forms of activity and interpersonal relations and culture, and by extension the relative material success of cultures), thus biologizing the notion of "race", as did Foucault demonstrate; third, that race is therefore a valid scientific category that can be used to explain and predict individual and group behavior. Races were distinguished by skin color, facial type, cranial profile and size, texture and color of hair. Moreover, races were almost universally considered to reflect group differences in moral character and intelligence.

The eugenics movement of the late 19th and early 20th centuries, inspired by Arthur Gobineau's An Essay on the Inequality of the Human Races (1853-1855), Vacher de Lapouge's "anthroposociology" and Herder's theories, asserted as self-evident the biological inferiority of particular groups (Kevles 1985). In many parts of the world, the idea of race became a way of rigidly dividing groups by use of culture as well as physical appearances (Hannaford 1996). Campaigns of oppression and genocide often used supposed racial differences to motivate inhuman acts against others (Horowitz 2001).

The advent of Darwinian models of evolution and Mendelian genetics, however, called into question the scientific validity of both characteristics, and required a radical reconsideration of race.

Race as subspecies
With the advent of the modern synthesis in the early 20th century, biologists developed a new, more rigorous model of race as subspecies. For these biologists, a race is a recognizable group forming all or part of a species. A monotypic species has no races, or rather one race comprising the whole species. Monotypic species can occur in several ways:


 * All members of the species are very similar and cannot be sensibly divided into biologically significant subcategories.
 * The individuals vary considerably but the variation is essentially random and largely meaningless so far as genetic transmission of these variations is concerned (many plant species fit into this category, which is why horticulturists interested in preserving, say, a particular flower color avoid propagation from seed, and instead use vegetative methods like propagation from cuttings).
 * The variation between individuals is noticeable and follows a pattern, but there are no clear dividing lines between separate groups: they fade imperceptibly into one another. Such clinal variation always indicates substantial gene flow between the apparently separate groups that make up the population(s). Populations that have a steady, substantial gene flow between them are likely to represent a monotypic species even when a fair degree of genetic variation is obvious.

A polytypic species has two or more races (or, in current parlance, two or more sub-types). This classification reflects separate groups that are clearly distinct from one another and do not generally interbreed (although there may be a relatively narrow hybridization zone), but which would interbreed freely if given the chance to do so. Although different species can sometimes interbreed to a limited extent, the converse is not true. Groups incapable of producing fertile offspring with each other are universally considered distinct species, and not merely different "races" of the same species.

Although this attempt at conceptual precision gained currency with many biologists, especially zoologists, evolutionary scientists have criticized it on a number of fronts.

The rejection of race and the rise of "population" and "cline"
At the beginning of the 20th century, anthropologists questioned, and subsequently abandoned, the claim that biologically distinct races are isomorphic with (related to) distinct linguistic, cultural, and social groups. Then, the rise of population genetics led some mainstream evolutionary scientists in anthropology and biology to question the very validity of race as scientific concept describing an objectively real phenomenon. Those who came to reject the validity of the concept, race, did so for four reasons: empirical, definitional, the availability of alternative concepts, and ethical (Lieberman and Byrne 1993).

The first to challenge the concept of race on empirical grounds were anthropologists Franz Boas, who demonstrated phenotypic plasticity due to environmental factors (Boas 1912) (see also ), and Ashley Montagu (1941, 1942), who relied on evidence from genetics. Zoologists Edward O. Wilson and W. Brown then challenged the concept from the perspective of general systematics, and further rejected the claim that "races" were equivalent to "subspecies" (Wilson and Brown 1953). Claude Lévi-Strauss's Race and History (UNESCO, 1952) enforced this cultural relativist thesis, by the famous metaphor of cultures as trains crossing each other in different directions, thus each one seeing the others as immobile while they themselves are progressing.

One of the crucial innovations in reconceptualizing genotypic and phenotypic variation was anthropologist C. Loring Brace's observation that such variations, insofar as they are affected by natural selection, migration, or genetic drift, are distributed along geographic gradations called "clines" (Brace 1964). This point called attention to a problem common to phenotypic-based descriptions of races (for example, those based on hair texture and skin color): they ignore a host of other similarities and difference (for example, blood type) that do not correlate highly with the markers for race. Thus, anthropologist Frank Livingstone's conclusion that, since clines cross racial boundaries, "there are no races, only clines" (Livingstone 1962: 279). In 1964, biologists Paul Ehrlich and Holm pointed out cases where two or more clines are distributed discordantly&mdash;for example, melanin is distributed in a decreasing pattern from the equator north and south; frequencies for the haplotype for beta-S hemoglobin, on the other hand, radiate out of specific geographical points in Africa (Ehrlich and Holm 1964). As anthropologists Leonard Lieberman and Fatimah Linda Jackson observe, "Discordant patterns of heterogeneity falsify any description of a population as if it were genotypically or even phenotypically homogeneous" (Lieverman and Jackson 1995).

Finally, geneticist Richard Lewontin, observing that 85 percent of human variation occurs within populations, and not between populations, argued that neither "race" nor "subspecies" was an appropriate or useful way to describe populations (Lewontin 1973). This view is described by its opponents as Lewontin's Fallacy. Some researchers report the variation between racial groups (measured by Sewall Wright's population structure statistic FST) accounts for as little as 5% of human genetic variation2. However, because of technical limitations of FST, many geneticists now believe that low FST values do not invalidate the suggestion that there might be different human races (Edwards, 2003). Meanwhile, neo-Marxists such as David Harvey (1982, 1984, 1992) believe that race is a social construct that in reality does not exist, used instead to extenuate class differences.

These empirical challenges to the concept of race forced evolutionary sciences to reconsider their definition of race. Mid-century, anthropologist William Boyd defined race as:
 * A population which differs significantly from other populations in regard to the frequency of one or more of the genes it possesses. It is an arbitrary matter which, and how many, gene loci we choose to consider as a significant "constellation" (Boyd 1950).

Lieberman and Jackson (1994) have pointed out that "the weakness of this statement is that if one gene can distinguish races then the number of races is as numerous as the number of human couples reproducing." Moreover, anthropologist Stephen Molnar has suggested that the discordance of clines inevitably results in a multiplication of races that renders the concept itself useless (Molnar 1992).

Alongside empirical and conceptual problems with "race" following the Second World War, evolutionary and social scientists were acutely aware of how beliefs about race had been used to justify discrimination, apartheid, slavery, and genocide. This questioning gained momentum in the 1960s during the American Civil Rights Movement and the emergence of numerous anti-colonial movements worldwide.

In the face of these issues, some evolutionary scientists have simply abandoned the concept of race in favor of "population." What distinguishes population from previous groupings of humans by race is that it refers to a breeding population (essential to genetic calculations) and not to a biological taxon. Other evolutionary scientists have abandoned the concept of race in favor of cline (meaning, how the frequency of a trait changes along a geographic gradient). The concepts of population and cline are not, however, mutually exclusive and both are used by many evolutionary scientists.

In the face of this rejection of race by some evolutionary scientists, many social scientists have replaced the word race with the word "ethnicity" to refer to self-identifying groups based on beliefs in shared religion, nationality, or race. Moreover, they understood these shared beliefs to mean that religion, nationality, and race itself are social constructs and have no objective basis in the supernatural or natural realm (Gordon 1964). See also the American Anthropological Association's Statement on Race.

Summary of different definitions of race
The United States government has provided definitions regarding race (see for example Race (U.S. Census)). Racial classification in the U.S. 2000 census was based solely on self-identification, did not pre-suppose disjointedness, and did not include a category "Hispanic," which is considered an ethnicity, rather than a race, by the U.S. Census. On the other hand, the EEOC explicitly defines Hispanics as a separate and distinct "race."

Origins of modern humans

 * see also single-origin hypothesis, multiregional hypothesis.



Any biological model for race must account for the development of racial differences during human evolution. For much of the 20th century, however, anthropologists relied on an incomplete fossil record for reconstructing human evolution. Their models seldom provided a firm basis for drawing inferences about the origin of races. Modern research in molecular biology, however, has provided evolutionary scientists with a whole new kind of data, which adds considerably to the knowledge of our past.

There has been considerable debate among anthropologists as to the origins of Homo sapiens. About a million years ago Homo erectus migrated out of Africa and into Europe and Asia. The debate hinges on whether Homo erectus evolved into Homo sapiens more or less simultaneously in Africa, Europe, and Asia, or whether Homo sapiens evolved only in Africa, and eventually supplanted Homo erectus in Europe and Asia. Each model suggests different possible scenarios for the evolution of distinct races.

Multiregional hypothesis
Advocates of the first scenario (see Frayer et al. 1993), the multiregional continuity evolution model, cite as evidence anatomical continuity in the fossil record in South Central Europe (Smith 1982), East Asia and Australia (Wolpoff 1993) (anatomical affinity is taken to suggest genetic affinity). They argue that very strong genetic similarities among all humans do not prove recent common ancestry, but rather reflect the interconnectedness of human populations around the world, resulting in relatively constant gene flow (Thorne and Wolpoff 1992). They further argue that this model is consistent with clinal patterns (Wolpoff 1993).

The most important element of this model for theories of race is that it allows a million years for the evolution of Homo sapiens around the world; this is more than enough time for the evolution of different races. Leiberman and Jackson (1995), however, have noted that this model depends on several findings relevant to race: (1) that marked morphological contrasts exist between individuals found at the center and at the perimeter of Middle Pleistocene range of the genus Homo; (2) that many features can be shown to emerge at the edge of that range before they develop at the center; and (3) that these features exhibit great tenacity through time. Regional variations in these features can thus be taken as evidence for long term differences among genus Homo individuals that prefigure different races among present-day Homo sapiens individuals.

Out of Africa


Information about the history of our species comes from two main sources: the paleoanthropological record and historical inferences based on current genetic differences observed in humans. Although both sources of information are fragmentary, they have been converging in recent years on the same general story.

Since the 1990s, it has become common to use multilocus genotypes to distinguish different human groups and to allocate individuals to groups (Bamshad et al. 2004). These data have led to an examination of the biological validity of races as evolutionary lineages and the description of races in cladistic terms. The technique of multilocus genotyping has been used to determine patterns of human demographic history. Thus, the concept of "race" afforded by these techniques is synonymous with ancestry, broadly understood.

Studies of human genetic variation imply that Africa was the ancestral source of all modern humans, and that Homo sapiens migrated out of Africa and displaced Homo erectus between 140,000 and 290,000 years ago (Cann et al. 1987). Indigenous Australians are believed to be an early out-group that remained isolated. Most other groups, including Europeans, Asians, and Native Americans, were found to be a single related (monophyletic) group resulting from a later out-migration from Africa, which could reasonably be divided into West and East Eurasian groups.

The existing fossil evidence suggests that anatomically modern humans evolved in Africa, within the last ∼200,000 years, from a pre-existing population of humans (Klein 1999). Although it is not easy to define "anatomically modern" in a way that encompasses all living humans and excludes all archaic humans (Lieberman et al. 2002), the generally agreed-upon physical characteristics of anatomical modernity include a high rounded skull, facial retraction, and a light and gracile, as opposed to heavy and robust, skeleton (Lahr 1996). Early fossils with these characteristics have been found in eastern Africa and have been dated to ∼160,000–200,000 years ago (White et al. 2003; McDougall et al. 2005). At that time, the population of anatomically modern humans appears to have been small and localized (Harpending et al. 1998). Much larger populations of archaic humans lived elsewhere in the Old World, including the Neandertals in Europe and an earlier species of humans, Homo erectus, in Asia (Swisher et al. 1994).

Fossils of the earliest anatomically modern humans found outside Africa are from two sites in the Middle East and date to a period of relative global warmth, ∼100,000 years ago, though this region was reinhabited by Neandertals in later millennia as the climate in the northern hemisphere again cooled (Lahr and Foley 1998). Groups of anatomically modern humans appear to have moved outside Africa permanently sometime >60,000 years ago. One of the earliest modern skeletons found outside Africa is Mungo Man, from Australia, and has been dated to ∼42,000 years ago (Bowler et al. 2003), although studies of environmental changes in Australia argue for the presence of modern humans in Australia >55,000 years ago (Miller et al. 1999). To date, the earliest anatomically modern skeleton discovered from Europe comes from the Carpathian Mountains of Romania and is dated to 34,000–36,000 years ago (Trinkaus et al. 2003).

Existing data on human genetic variation support and extend conclusions based on the fossil evidence. African populations exhibit greater genetic diversity than do populations in the rest of the world, implying that humans appeared first in Africa and later colonized Eurasia and the Americas (Tishkoff and Williams 2002; Yu et al. 2002; Tishkoff and Verrelli 2003). The genetic variation seen outside Africa is generally a subset of the variation within Africa, a pattern that would be produced if the migrants from Africa were limited in number and carried just part of African genetic variability with them (Cavalli-Sforza and Feldman 2003). Patterns of genetic variation suggest an earlier population expansion in Africa followed by a subsequent expansion in non-African populations, and the dates calculated for the expansions generally coincide with the archaeological record (Jorde et al. 1998).

Aspects of the relationship between anatomically modern and archaic humans remain contentious. Studies of mtDNA (Ingman et al. 2000), the Y chromosome (Underhill et al. 2000), portions of the X chromosome (Kaessmann et al. 1999), and many (though not all) autosomal regions (Harpending and Rogers 2000) support the "Out of Africa" account of human history, in which anatomically modern humans appeared first in eastern Africa and then migrated throughout Africa and into the rest of the world, with little or no interbreeding between modern humans and the archaic populations they gradually replaced (Tishkoff et al. 2000; Stringer 2002). However, several groups of researchers cite fossil and genetic evidence to argue for a more complex account. They contend that humans bearing modern traits emerged several times from Africa, over an extended period, and mixed with archaic humans in various parts of the world (Hawks et al. 2000; Eswaran 2002; Templeton 2002; Ziętkiewicz et al. 2003). As a result, they say, autosomal DNA from archaic human populations living outside Africa persists in modern populations, and modern populations in various parts of the world still bear some physical resemblance to the archaic populations that inhabited those regions (Wolpoff et al. 2001).

However, distinguishing possible contributions to the gene pool of modern humans from archaic humans outside Africa is difficult, especially since many autosomal loci coalesce at times preceding the separation of archaic human populations (Pääbo 2003). In addition, studies of mtDNA from archaic and modern humans and extant Y chromosomes suggest that any surviving genetic contributions of archaic humans outside Africa must be small, if they exist at all (Krings et al. 1997; Nordborg 1998; Takahata et al. 2001; Serre et al. 2004). The observation that most genes studied to date coalesce in African populations points toward the importance of Africa as the source of most modern genetic variation, perhaps with some subdivision in the ancestral African population (Satta and Takahata 2002). Sequence data for hundreds of loci from widely distributed worldwide populations eventually may clarify the population processes associated with the appearance of anatomically modern humans (Wall 2000), as well as the amount of gene flow among modern humans since then.

Cladistics
A phylogenetic tree like the one shown above is usually derived from DNA or protein sequences from populations. Often mitochondrial DNA or Y chromosome sequences are used to study ancient human demographics. These single-locus sources of DNA do not recombine and are almost always inherited from a single parent, with only one known exception in mtDNA (Schwartz and Vissing 2002). Individuals from the various continental groups tend to be more similar to one another than to people from other continents. The tree is rooted in the common ancestor of chimpanzees and humans, which is believed to have originated in Africa. Horizontal distance corresponds to two things:


 * 1) Genetic distance. Given below the diagram, the genetic difference between humans and chimps is roughly 2%, or 20 times larger than the variation among modern humans.
 * 2) Temporal remoteness of the most recent common ancestor. Rough estimates are given above the diagram, in millions of years. The mitochondrial most recent common ancestor of modern humans lived roughly 200,000 years ago, latest common ancestors of humans and chimps between four and seven million years ago.

Chimpanzees and humans belong to different genera, indicated in red. Formation of species and subspecies is also indicated, and the formation of "races" is indicated in the green rectangle to the right (note that only a very rough representation of human phylogeny is given). Note that vertical distances are not meaningful in this representation.

Distribution of variation
A thorough description of the differences in patterns of genetic variation between humans and other species awaits additional genetic studies of human populations and nonhuman species. But the data gathered to date suggest that human variation exhibits several distinctive characteristics. First, compared with many other mammalian species, humans are genetically less diverse—a counterintuitive finding, given our large population and worldwide distribution (Li and Sadler 1991; Kaessmann et al. 2001). For example, the chimpanzee subspecies living just in central and western Africa have higher levels of diversity than do humans (Ebersberger et al. 2002; Yu et al. 2003; Fischer et al. 2004).

Two random humans are expected to differ at approximately 1 in 1000 nucleotides, whereas two random chimpanzees differ at 1 in 500 nucleotide pairs. However, with a genome of approximate 3 billion nucleotides, on average two humans differ at approximately 3 million nucleotides. Most of these single nucleotide polymorphisms (SNPs) are neutral, but some are functional and influence the phenotypic differences between humans. It is estimated that about 10 million SNPs exist in human populations, where the rarer SNP allele has a frequency of at least 1% (see International HapMap Project).

The distribution of variants within and among human populations also differs from that of many other species. The details of this distribution are impossible to describe succinctly because of the difficulty of defining a "population," the clinal nature of variation, and heterogeneity across the genome (Long and Kittles 2003). In general, however, 5%–15% of genetic variation occurs between large groups living on different continents, with the remaining majority of the variation occurring within such groups (Lewontin 1972; Jorde et al. 2000a; Hinds et al. 2005). This distribution of genetic variation differs from the pattern seen in many other mammalian species, for which existing data suggest greater differentiation between groups (Templeton 1998; Kittles and Weiss 2003).

In the field of population genetics, it is believed that the distribution of neutral polymorphisms among contemporary humans reflects human demographic history.

Our history as a species also has left genetic signals in regional populations. For example, in addition to having higher levels of genetic diversity, populations in Africa tend to have lower amounts of linkage disequilibrium than do populations outside Africa, partly because of the larger size of human populations in Africa over the course of human history and partly because the number of modern humans who left Africa to colonize the rest of the world appears to have been relatively low (Gabriel et al. 2002). In contrast, populations that have undergone dramatic size reductions or rapid expansions in the past and populations formed by the mixture of previously separate ancestral groups can have unusually high levels of linkage disequilibrium (Nordborg and Tavare 2002).

In the field of population genetics, it is believed that the distribution of neutral polymorphisms among contemporary humans reflects human demographic history. It is believed that humans passed through a population bottleneck before a rapid expansion coinciding with migrations out of Africa leading to an African-Eurasian divergence around 100,000 years ago (ca. 5,000 generations), followed by a European-Asian divergence about 40,000 years ago (ca. 2,000 generations).

The rapid expansion of a previously small population has two important effects on the distribution of genetic variation. First, the so-called founder effect occurs when founder populations bring only a subset of the genetic variation from their ancestral population. Second, as founders become more geographically separated, the probability that two individuals from different founder populations will mate becomes smaller. The effect of this assortative mating is to reduce gene flow between geographical groups, and to increase the genetic distance between groups. The expansion of humans from Africa affected the distribution of genetic variation in two other ways. First, smaller (founder) populations experience greater genetic drift because of increased fluctuations in neutral polymorphisms. Second, new polymorphisms that arose in one group were less likely to be transmitted to other groups as gene flow was restricted.

Many other geographic, climatic, and historical factors have contributed to the patterns of human genetic variation seen in the world today. For example, population processes associated with colonization, periods of geographic isolation, socially reinforced endogamy, and natural selection all have affected allele frequencies in certain populations (Jorde et al. 2000b; Bamshad and Wooding 2003). In general, however, the recency of our common ancestry and continual gene flow among human groups have limited genetic differentiation in our species.

Substructure in the human population


New data on human genetic variation has reignited the debate surrounding race. Most of the controversy surrounds the question of how to interpret these new data, and whether conclusions based on existing data are sound. A large majority of researchers endorse the view that continental groups do not constitute different subspecies. However, other researchers still debate whether evolutionary lineages should rightly be called "races". These questions are particularly pressing for biomedicine, where self-described race is often used as an indicator of ancestry (see race in biomedicine below).

Modern biological evidence from the anthropological textbook Human Species (2003) contradicts earlier theories of which groups were more genetically related to other groups. Humans are all related. Humanity divided itself into the African and the Eurasian/Oceanic branch. The Eurasian and Oceanic branches are the products of this common origin. The Eurasian branch split into the Amerindian and major East Asian branch. The major East Asian branch divided itself into eastern Russian and the East Asian. The Oceanic branch divided itself into the Southeast Asians and Pacific Islanders. 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 south 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.

Although the genetic differences among human groups are relatively small, these differences in certain genes such as duffy, ABCC11, SLC24A5, called ancestry-informative markers (AIMs) nevertheless can be used to reliably situate many individuals within broad, geographically based groupings or self-identified race. For example, computer analyses of hundreds of polymorphic loci sampled in globally distributed populations have revealed the existence of genetic clustering that roughly is associated with groups that historically have occupied large continental and subcontinental regions (Rosenberg et al. 2002; Bamshad et al. 2003).

Some commentators have argued that these patterns of variation provide a biological justification for the use of traditional racial categories. They argue that the continental clusterings correspond roughly with the division of human beings into sub-Saharan Africans; Europeans, western Asians, and northern Africans; eastern Asians; Polynesians and other inhabitants of Oceania; and Native Americans (Risch et al. 2002). Other observers disagree, saying that the same data undercut traditional notions of racial groups (King and Motulsky 2002; Calafell 2003; Tishkoff and Kidd 2004). They point out, for example, that major populations considered races or subgroups within races do not necessarily form their own clusters. Thus, samples taken from India and Pakistan affiliate with Europeans or eastern Asians rather than separating into a distinct cluster.

Furthermore, because human genetic variation is clinal, many individuals affiliate with two or more continental groups. Thus, the genetically based "biogeographical ancestry" assigned to any given person generally will be broadly distributed and will be accompanied by sizable uncertainties (Pfaff et al. 2004).

In many parts of the world, groups have mixed in such a way that many individuals have relatively recent ancestors from widely separated regions. Although genetic analyses of large numbers of loci can produce estimates of the percentage of a person's ancestors coming from various continental populations (Shriver et al. 2003; Bamshad et al. 2004), these estimates may assume a false distinctiveness of the parental populations, since human groups have exchanged mates from local to continental scales throughout history (Cavalli-Sforza et al. 1994; Hoerder 2002). Even with large numbers of markers, information for estimating admixture proportions of individuals or groups is limited, and estimates typically will have wide CIs (Pfaff et al. 2004).

For the paternal and maternal genetic lineages of the world, see: and

Physical variation in humans
The distribution of many physical traits resembles the distribution of genetic variation within and between human populations (American Association of Physical Anthropologists 1996; Keita and Kittles 1997). For example, ∼90% of the variation in human head shapes occurs within every human group, and ∼10% separates groups, with a greater variability of head shape among individuals with recent African ancestors (Relethford 2002).

A prominent exception to the common distribution of physical characteristics within and among groups is skin color. Approximately 10% of the variance in skin color occurs within groups, and ~90% occurs between groups (Relethford 2002). This distribution of skin color and its geographic patterning—with people whose ancestors lived predominantly near the equator having darker skin than those with ancestors who lived predominantly in higher latitudes—indicate that this attribute has been under strong selective pressure. Darker skin appears to be strongly selected for in equatorial regions to prevent sunburn, skin cancer, the photolysis of folate, and damage to sweat glands (Sturm et al. 2001; Rees 2003). A leading hypothesis for the selection of lighter skin in higher latitudes is that it enables the body to form greater amounts of vitamin D, which helps prevent rickets (Jablonski 2004). Evidence for this includes the finding that a substantial portion of the differences of skin color between Europeans and Africans resides in a single gene, SLC24A5 the threonine-111 allele of which was found in 98.7 to 100% among several European samples, while the alanine-111 form was found in 93 to 100% of samples of Africans, East Asians and Indigenous Americans (Lamason et al. 2005). However, the vitamin D hypothesis is not universally accepted (Aoki 2002), and lighter skin in high latitudes may correspond simply to an absence of selection for dark skin (Harding et al. 2000). Melanin which serves as the pigment, is located in the epidermis of the skin, and is based on hereditary gene expression.

Because skin color has been under strong selective pressure, similar skin colors can result from convergent adaptation rather than from genetic relatedness. Sub-Saharan Africans, tribal populations from southern India, and Indigenous Australians have similar skin pigmentation, but genetically they are no more similar than are other widely separated groups. Furthermore, in some parts of the world in which people from different regions have mixed extensively, the connection between skin color and ancestry has been substantially weakened (Parra et al. 2004). In Brazil, for example, skin color is not closely associated with the percentage of recent African ancestors a person has, as estimated from an analysis of genetic variants differing in frequency among continent groups (Parra et al. 2003).

Considerable speculation has surrounded the possible adaptive value of other physical features characteristic of groups, such as the constellation of facial features observed in many eastern and northeastern Asians (Guthrie 1996). However, any given physical characteristic generally is found in multiple groups (Lahr 1996), and demonstrating that environmental selective pressures shaped specific physical features will be difficult, since such features may have resulted from sexual selection for individuals with certain appearances or from genetic drift (Roseman 2004).

Social interpretations of race
Historians, anthropologists and social scientists often describe human races as a social construct, preferring instead the term population, which can be given a clear operational definition. Even those who reject the formal concept of race, however, still use the word race in day-to-day speech. This may either be a matter of semantics, or an effect of an underlying cultural significance of race in racist societies. Regardless of the name, a working concept of sub-species grouping can be useful, because in the absence of cheap and widespread genetic tests, various race-linked gene mutations (see Cystic fibrosis, Lactose intolerance, Tay-Sachs Disease and Sickle cell anemia) are difficult to address without recourse to a category between "individual" and "species".

In everyday speech, race often describes populations better defined as ethnic groups, often leading to discrepancies between scientific views on race and popular usage of the term. For instance in many parts of the United States, categories such as Hispanic or Latino are viewed to constitute a race, though others see Hispanic as a linguistic and cultural grouping coming from a variety of backgrounds. In Europe, such a distinction, suggesting that South Europeans are not European or white, would seem odd at least or possibly even insulting. In the United States, in what is referred to as the one-drop rule, the term Black subsumes people with a broad range of ancestries under one label, even though many who are termed Black could be more accurately described as white through simple anthropologic or taxonomic method. In much of Europe groups such as Roma and Turks are commonly defined as racially distinct from White Europeans, though these groups could be considered "Caucasian" by old physical anthropological methods which employed finite nose measurements as the standard form of racial classifaction.

Some argue it is preferable when considering biological relations to think in terms of populations, and when considering cultural relations to think in terms of ethnicity, rather than of race. Instead of classing people into one "group", say "Caucasians" or Europeans you have Britons, Frenchmen, Germans, Nords, western Slavs and Celts rather than having a term implying a (possible) ancestry group in the Caucasus which is definitely too distant for any real consideration, and moreover reaching to groups including eastern Slavs, Roma, as well as Georgians, and others who differ notably, both in culture, and to a noteworthy extent in physical appearance, from the aforementioned ethnic groups. There can be as much difference between two ethnicities grouped into a single "race" as there can be between ethnicities grouped (often arbitrarily) into an another "race".

These developments had important consequences. For example, some scientists developed the notion of "population" to take the place of race. This substitution is not simply a matter of exchanging one word for another. Populations are, in a sense, simply statistical clusters that emerge from the choice of variables of interest; there is no preferred set of variables. The "populationist" view does not deny that there are physical differences among peoples; it simply claims that the historical conceptions of "race" are not particularly useful in accounting for these differences scientifically.

Since the 1960s, some anthropologists and teachers of anthropology have re-conceived "race" as a cultural category or social construct, in other words, as a particular way that some people have of talking about themselves and others. As such it cannot be a useful analytical concept; rather, the use of the term "race" itself must be analyzed. Moreover, they argue that biology will not explain why or how people use the idea of race: history and social relationships will.

Racial and ethnic diversity in the post-Columbian New World
Even as the idea of "race" was becoming a powerful organizing principle in many societies, the shortcomings of the concept were apparent. In the Old World, the gradual transition in appearances from one group to adjacent groups emphasized that "one variety of mankind does so sensibly pass into the other, that you cannot mark out the limits between them," as Blumenbach observed in his writings on human variation (Marks 1995, p. 54). In parts of the Americas, the situation was somewhat different. The immigrants to the New World came largely from widely separated regions of the Old World—western and northern Europe, western Africa, and, later, eastern Asia and southern Europe. In the Americas, the immigrant populations began to mix among themselves and with the indigenous inhabitants of the continent. In the United States, for example, most people who self-identify as African American have some European ancestors—in one analysis of genetic markers that have differing frequencies between continents, European ancestry ranged from an estimated 7% for a sample of Jamaicans to ∼23% for a sample of African Americans from New Orleans (Parra et al. 1998). Similarly, many people who identify as European American have some African or Native American ancestors, either through openly interracial marriages or through the gradual inclusion of people with mixed ancestry into the majority population. In a survey of college students who self-identified as white in a northeastern U.S. university, ∼30% were estimated to have <90% European ancestry (Shriver et al. 2003).

In the United States, social and legal conventions developed over time that forced individuals of mixed ancestry into simplified racial categories (Gossett 1997). An example is the "one-drop rule" implemented in some state laws that treated anyone with a single known African American ancestor as black (Davis 2001). The decennial censuses conducted since 1790 in the United States also created an incentive to establish racial categories and fit people into those categories (Nobles 2000). In other countries in the Americas where mixing among groups was more extensive, social categories have tended to be more numerous and fluid, with people moving into or out of categories on the basis of a combination of socioeconomic status, social class, ancestry, and appearance (Mörner 1967).

Efforts to sort the increasingly mixed population of the United States into discrete categories generated many difficulties (Spickard 1992). By the standards used in past censuses, many millions of children born in the United States have belonged to a different race than have one of their biological parents. Efforts to track mixing between groups led to a proliferation of categories (such as "mulatto" and "octoroon") and "blood quantum" distinctions that became increasingly untethered from self-reported ancestry. A person's racial identity can change over time, and self-ascribed race can differ from assigned race (Kressin et al. 2003). Until the 2000 census, Latinos were required to identify with a single race despite the long history of mixing in Latin America; partly as a result of the confusion generated by the distinction, 42% of Latino respondents in the 2000 census ignored the specified racial categories and checked "some other race" (Mays et al. 2003).

Race in the United States
In the United States since its early history, Native Americans, African-Americans and European-Americans were classified as belonging to different races. For nearly three centuries, the criteria for membership in these groups were similar, comprising a person’s appearance, his fraction of known non-White ancestry, and his social circle.2 But the criteria for membership in these races diverged in the late 19th century. During Reconstruction, increasing numbers of Americans began to consider anyone with "one drop" of "Black blood" to be Black.3 By the early 20th century, this notion of invisible blackness was made statutory in many states and widely adopted nationwide.4 In contrast, Amerindians continue to be defined by a certain percentage of "Indian blood" (called blood quantum) due in large part to American slavery ethics. Finally, for the past century or so, to be White one had to have "pure" White ancestry. (Utterly European-looking Americans of Hispanic or Arab ancestry are exceptions in being seen as White by most Americans despite traces of known African ancestry.)

The difference between how Native American and Black identities are defined today (blood quantum versus one-drop) has demanded explanation. According to anthropologists such as Gerald Sider, the goal of such racial designations was to concentrate power, wealth, privilege and land in the hands of Whites in a society of White hegemony and White privilege (Sider 1996; see also Fields 1990). The differences have little to do with biology and far more to do with the history of racism and specific forms of White supremacy (the social, geopolitical and economic agendas of dominant Whites vis-à-vis subordinate Blacks and Native Americans) especially the different roles Blacks and Amerindians occupied in White-dominated nineteenth-century America. The theory suggests that that the blood quantum definition of Native American identity enabled Whites to acquire Amerindian lands, while the one-drop rule of Black identity enabled Whites to preserve their agricultural labor force. The contrast presumably emerged because as peoples transported far from their land and kinship ties on another continent, Black labor was relatively easy to control, thus reducing Blacks to valuable commodities as agricultural laborers. In contrast, Amerindian labor was more difficult to control; moreover, Amerindians occupied large territories that became valuable as agricultural lands, especially with the invention of new technologies such as railroads; thus, the blood quantum definition enhanced White acquisition of Amerindian lands in a doctrine of Manifest Destiny that subjected them to marginalization and multiple episodic localized campaigns of extermination.

The political economy of race had different consequences for the descendants of aboriginal Americans and African slaves. The 19th-century blood quantum rule meant that it was relatively easier for a person of mixed Euro-Amerindian ancestry to be accepted as White. The offspring of only a few generations of intermarriage between Amerindians and Whites likely would not have been considered Amerindian at all&mdash;at least not in a legal sense. Amerindians could have treaty rights to land, but because an individual with one Amerindian great-grandparent no longer was classified as Amerindian, they lost any legal claim to Amerindian land. According to the theory, this enabled Whites to acquire Amerindian lands. The irony is that the same individuals who could be denied legal standing because they were "too White" to claim property rights, might still be Amerindian enough to be considered as "breeds," stigmatized for their Native American ancestry.

The 20th-century one-drop rule, on the other hand, made it relatively difficult for anyone of known Black ancestry to be accepted as White. The child of an African-American sharecropper and a White person was considered Black. And, significant in terms of the economics of sharecropping, such a person also would likely be a sharecropper as well, thus adding to the employer's labor force.

In short, this theory suggests that in a 20th-century economy that benefited from sharecropping, it was useful to have as many Blacks as possible. Conversely, in a 19th-century nation bent on westward expansion, it was advantageous to diminish the numbers of those who could claim title to Amerindian lands by simply defining them out of existence.

It must be mentioned, however, that although some scholars of the Jim Crow period agree that the 20th-century notion of invisible Blackness shifted the color line in the direction of paleness, thereby swelling the labor force in response to Southern Blacks' great migration northwards, others (Joel Williamson, C. Vann Woodward, George M. Fredrickson, Stetson Kennedy) see the one-drop rule as a simple consequence of the need to define Whiteness as being pure, thus justifying White-on-Black oppression. In any event, over the centuries when Whites wielded power over both Blacks and Amerindians and widely believed in their inherent superiority over people of color, it is no coincidence that the hardest racial group in which to prove membership was the White one.

The term "Hispanic" as an ethnonym emerged in the twentieth century with the rise of migration of laborers from Spanish-speaking countries to the United States; it thus includes people who had been considered racially distinct (Black, White, Amerindian) in their home countries. Today, the word "Latino" is often used as a synonym for "Hispanic" (the identification of Spanish-speaking countries in the Americas as "Latin America" was first promoted by supporters of Maximilian as emperor of Mexico in 1864. Maximilian was installed by the French emperor Napoleon III as a way of extending French influence in the Americas; since French and Spanish are both derived from Latin, the French identified Spanish-speakers as "Latin" in order to emphasize a fictive kinship with the French, and in the hope &mdash; unfulfilled &mdash; of legitimating Maximilian). In contrast to "Latino," "Anglo" is now used in a similar way to refer to the descendants of British colonists, and values and practices derived from British culture.

Race Definitions in the United States: ''Source: U.S. Census Bureau, 2000 Census of Population, Public Law 94-171 Redistricting Data File. Updated every 10 years.'' http://quickfacts.census.gov/qfd/meta/long_68178.htm

The concept of race as used by the Census Bureau reflects self-identification by people according to the race or races with which they most closely identify. These categories are sociopolitical constructs and should not be interpreted as being scientific or anthropological in nature. They change from one census to another, and the racial categories include both racial and national-origin groups.

The racial classifications used by the Census Bureau adhere to the October 30,1997, Federal Register Notice entitled,"Revisions to the Standards for the Classification of Federal Data on Race and Ethnicity" issued by the Office of Management and Budget (OMB).


 * 1) American Indian and Alaska Native. A person having origins in any of the original peoples of North and South America (including Central America) and who maintain tribal affiliation or community attachment.
 * 2) White. A person having origins in any of the original peoples of Europe, the Middle East, or North Africa. It includes people who indicate their race as "White" or report entries such as Irish, German, Italian, Lebanese, Near Easterner, Arab, or Polish.
 * 3) Black or African American. A person having origins in any of the Black racial groups of Africa. It includes people who indicate their race as "Black, African Am., or Negro," or provide written entries such as African American, Afro American, Kenyan, Nigerian, or Haitian.
 * 4) Asian. A person having origins in any of the original peoples of the Far East, Southeast Asia, or the Indian subcontinent including, for example, Cambodia, China, India, Japan, Korea, Malaysia, Pakistan, the Philippine Islands, Thailand, and Vietnam. It includes "Asian Indian," "Chinese," "Filipino," "Korean," "Japanese," "Vietnamese," and "Other Asian."
 * 5) Native Hawaiian and Other Pacific Islander. A person having origins in any of the original peoples of Hawaii, Guam, Samoa, or other Pacific Islands. It includes people who indicate their race as "Native Hawaiian," "Guamanian or Chamorro," "Samoan," and "Other Pacific Islander."
 * 6) Hispanic. People from Spanish-speaking countries, or the descendants of people from Spanish speaking countries.  People who are identified as Black or Amerindian in their country of origin are often reclassified as Hispanic in the United States.
 * 7) Other. Includes all other responses not included in the "White", "Black or African American", "American Indian and Alaska Native", "Asian" and "Native Hawaiian and Other Pacific Islander" race categories described above. Respondents providing write-in entries such as multiracial, mixed, interracial, Wesort, or a Hispanic/Latino group (for example, Mexican, Puerto Rican, or Cuban) in the "Some other race" category are included here.
 * 8) Two or more races People may have chosen to provide two or more races either by checking two or more race response check boxes, by providing multiple write-in responses, or by some combination of check boxes and write-in responses.

Race in Brazil
Compared to 19th-century United States, 20th-century Brazil was characterized by a relative absence of sharply defined racial groups. This pattern reflects a different history and different social relations. Basically, race in Brazil was "biologized," but in a way that recognized the difference between ancestry (which determines genotype) and phenotypic differences. There, racial identity was not governed by a rigid descent rule. A Brazilian child was never automatically identified with the racial type of one or both parents, nor were there only two categories to choose from. Over a dozen racial categories would be recognized in conformity with the combinations of hair color, hair texture, eye color, and skin color. These types grade into each other like the colors of the spectrum, and no one category stands significantly isolated from the rest. That is, race referred to appearance, not heredity.

Through this system of racial identification, parents and children and even brothers and sisters were frequently accepted as representatives of opposite racial types. In a fishing village in the state of Bahia, an investigator showed 100 people pictures of three sisters and were asked to identify the races of each. In only six responses were the sisters identified by the same racial term. Fourteen responses used a different term for each sister. In another experiment nine portraits were shown to a hundred people. Forty different racial types were elicited. It was found, in addition, that a given Brazilian might be called by as many as thirteen different terms by other members of the community. These terms are spread out across practically the entire spectrum of theoretical racial types. A further consequence of the absence of a descent rule was that Brazilians apparently not only disagreed about the racial identity of specific individuals, but they also seemed to be in disagreement about the abstract meaning of the racial terms as defined by words and phrases. For example, 40% of a sample ranked moreno claro as a lighter type than mulato claro, while 60% reversed this order. A further note of confusion is that one person might employ different racial terms to describe the same person over a short time span. The choice of which racial description to use may vary according to both the personal relationships and moods of the individuals involved. The Brazilian census lists one's race according to the preference of the person being interviewed. As a consequence, hundreds of races appeared in the census results, ranging from blue (which is blacker than the usual black) to green (which is whiter than the usual white).

However, Brazilians are not so naive to ignore one's racial origins just because of his (or her) better social status. An interesting example of this phenomenon has occurred recently, when the famous soccer player Ronaldo declared publicly that he considered himself as white, thus linking racism to a form or another of class conflict. This caused a series of ironic notes on newspapers, which pointed out that he should have been proud of his African origin (which is obviously noticeable), a fact that must have made life for him (and for his ancestors) more difficult, so, being a successful personality was, in spite of that, a victory for him. What occurs in Brazil that differentiates it largely from the US or South Africa, for example, is that black or mixed-race people are, in fact, more accepted in social circles if they have more education, or have a successful life (an euphemism for "having a better salary").

So, although the identification of a person by race is far more fluid and flexible in Brazil than in the U.S., there still are racial stereotypes and prejudices. African features have been considered less desirable; Blacks have been considered socially inferior, and Whites superior. These white supremacist values seem to be an obvious legacy of European colonization and the slave-based plantation system. The complexity of racial classifications in Brazil is reflective of the extent of miscegenation in Brazilian society, which remains highly, but not strictly, stratified along color lines. Henceforth, Brazilian's myth of a perfect "post-racist" country, composed of the "cosmic race" celebrated in 1925 by José Vasconcelos, must be met with caution, as did sociologist Gilberto Freyre demonstrated in 1933 in Casa Grande e Senzala.

Race in politics and ethics
Michel Foucault showed the popular historical and political use of a non-essentialist notion of "race" used in the "race struggle" discourse during the 1688 Glorious Revolution and under Louis XIV's end of reign (See above). In the 19th century, this discourse developed in two different directions: marxism, which seize the notion and transformed it into "class struggle" discourse, and racists biologists and eugenicists who paved the way for 20th century "state racism".

During the Enlightenment, racial classifications were used to justify enslavement of those deemed to be of "inferior", non-White races, and thus supposedly best fitted for lives of toil under White supervision. These classifications made the distance between races seem nearly as broad as that between species, easing unsettling questions about the appropriateness of such treatment of humans. The practice was at the time generally accepted by both scientific and lay communities.

Arthur Gobineau's An Essay on the Inequality of the Human Races (1853-1855) was one of the milestone in the new racist discourse, along with Vacher de Lapouge's "anthroposociology" and Herder, who applied race to nationalist theory to develop militant ethnic nationalism. They posited the historical existence of national races such as German and French, branching from basal races supposed to have existed for millennia, such as the Aryan race, and believed political boundaries should mirror these supposed racial ones.

Later, one of Hitler's favorite sayings was, "Politics is applied biology". Hitler's ideas of racial purity led to unprecedented atrocities in Europe. Since then, ethnic cleansing has occurred in the Balkans and Rwanda. In one sense, ethnic cleansing is another name for the tribal warfare and mass murder that has afflicted human society for ages, but these crimes seem to gain intensity when believed to be scientifically sanctioned.

Racial inequality has been a concern of United States politicians and legislators since the country's founding. In the 19th century most White Americans (including abolitionists) explained racial inequality as an inevitable consequence of biological differences. Since the mid-20th century, political and civic leaders as well as scientists have debated to what extent racial inequality is cultural in origin. Some argue that current inequalities between Blacks and Whites are primarily cultural and historical, the result of past racism, slavery and segregation, and could be redressed through such programs as affirmative action and Head Start. Others work to reduce tax funding of remedial programs for minorities. They have based their advocacy on aptitude test data that, according to them, shows that racial ability differences are biological in origin and cannot be leveled even by intensive educational efforts. In electoral politics, many more ethnic minorities have won important offices in Western nations than in earlier times, although the highest offices tend to remain in the hands of Whites.

In his famous Letter from Birmingham Jail, the Rev. Dr. Martin Luther King Jr. observed:
 * History is the long and tragic story of the fact that privileged groups seldom give up their privileges voluntarily. Individuals may see the moral light and voluntarily give up their unjust posture; but as Reinhold Niebuhr has reminded us, groups are more immoral than individuals.

Dr. King's hope, expressed in his I Have a Dream speech, was that the civil rights struggle would one day produce a society where people were not "judged by the color of their skin, but by the content of their character."

Because of the identification of the concept of race with political oppression, many natural and social scientists today are wary of using race to describe human variation. Some, however, argue that race is nevertheless of continuing utility and validity in scientific research. Science and politics frequently take opposite sides in debates that relate to human intelligence and biomedicine.

Race and intelligence

 * Main article: Race and intelligence

Researchers have reported significant differences in the average IQ test scores of various ethnic groups. The interpretation and causes of these differences are controversial. Some researchers, such as Arthur Jensen, Richard Herrnstein, and Richard Lynn have argued that such differences are at least partially genetic. Others, such as Stephen Jay Gould and Richard Lewontin, believe categories such as "race" and "intelligence" are cultural constructs that render this sort of research scientifically flawed. Some, for example Thomas Sowell, bypass the issue of the origins of categorization and seek to explain test score gaps in terms of social differences that affect how much of one's innate capacities any individual person might achieve.

Race in biomedicine

 * Main article: Race in biomedicine

There is an active debate among biomedical researchers about the meaning and importance of race in their research. The primary impetus for considering race in biomedical research is the possibility of improving the prevention and treatment of diseases by predicting hard-to-ascertain factors on the basis of more easily ascertained characteristics. The most well-known examples of genetically-determined disorders that vary in incidence between ethnic groups would be sickle cell disease and thalassaemia among black and Mediterranean populations and Tay-Sachs disease among people of Ashkenazi Jewish descent. Some fear that the use of racial labels in biomedical research runs the risk of unintentionally exacerbating health disparities, so they suggest alternatives to the use of racial taxonomies.

Race in law enforcement


In an attempt to provide general descriptions that may facilitate the job of law enforcement officers seeking to apprehend suspects, the United States FBI employs the term "race" to summarize the general appearance (skin color, hair texture, eye shape, and other such easily noticed characteristics) of individuals whom they are attempting to apprehend. From the perspective of law enforcement officers, it is generally more important to arrive at a description that will readily suggest the general appearance of an individual than to make a scientifically valid categorization. Thus in addition to assigning a wanted individual to a racial category, such a description will include: height, weight, eye color, scars and other distinguishing characteristics, etc. Scotland Yard use a classification based in the ethnic background of British society: W1 (White-British), W2 (White-Irish), W9 (Any other white background); M1 (White and black Caribbean), M2 (White and black African), M3 (White and Asian), M9 (Any other mixed background); A1 (Asian-Indian), A2 (Asian-Pakistani), A3 (Asian-Bangladeshi), A9 (Any other Asian background); B1 (Black Caribbean), B2 (Black African), B3 (Any other black background); O1 (Chinese), O9 (Any other).

In many countries, the state is legally banned from maintaining data based on race, which often makes the police issue wanted notices to the public that include labels like "dark skin complexion", etc. There is controversy over the actual relationship between crimes, their assigned punishments, and the division of people into the so called "races." In the United States, the practice of racial profiling has been ruled to be both unconstitutional and also to constitute a violation of civil rights. There is active debate regarding the cause of a marked correlation between the recorded crimes, punishments meted out, and the country's "racially divided" people. Many consider de facto racial profiling an example of institutional racism in law enforcement.

More recent work in racial taxonomy based on DNA cluster analysis (See Lewontin's Fallacy) has led law enforcement to pursue suspects based on their racial classification as derived from their DNA evidence left at the crime scene. While controversial, DNA analysis has been successful in helping police identify the race of both victims and perpetrators. . In an attempt to be less subjective, this classification is called "biogeographical ancestry" rather than "race", but the terms for the BGA categories are the same. The difference is that ancestry-informative DNA markers identify continent-of-ancestry admixture, not ethnic self-identity. Hence, they cannot match the U.S. "races". For example, the DNA of an Arab-American, an African-American, and a Hispanic of precisely the same Afro-European genetic admixture would be "racially" indistinguishable. And a "White" woman with, say, 12 percent African ancestry (like Carol Channing) would show exactly the same BGA as a "Black" man of the same admixture (like Gregory Howard Williams).