Race

The term race refers to the concept of dividing people into populations or groups on the basis of various sets of characteristics and beliefs about common ancestry. AAPA Statement on Biological Aspects of Race America Association of Physical Anthropologists (AAPA). The most widely used human racial categories are based on visible traits (especially skin color, facial features and hair texture), and self-identification. "Does Race Exist?", Scientific American Magazine.

Conceptions of race, as well as specific ways of grouping races, vary by culture and over time, and are often controversial for scientific as well as social and political reasons. The controversy ultimately revolves around whether or not races are natural kinds or socially constructed, and the degree to which observed differences in ability and achievement, categorised on the basis of race, are a product of inherited (i.e. genetic) traits or environmental, social and cultural factors.

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Some argue that although "race" is a valid taxonomic concept in other species, it cannot be applied to humans. S O Y Keita, R A Kittles, C D M Royal, G E Bonney, P Furbert-Harris, G M Dunston & C N Rotimi, 2004 "Conceptualizing human variation" in Nature Genetics 36, S17 - S20 Conceptualizing human variation Mainstream scientists have argued that race definitions are imprecise, arbitrary, derived from custom, have many exceptions, have many gradations, and that the numbers of races delineated vary according to the culture making the racial distinctions; they thus reject the notion that any definition of race pertaining to humans can have taxonomic rigour and validity. whereas a new opinion among geneticists is that it should be a valid mean of classification, although in a modified form based on DNA analysis. [1][2][3][4]

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History

Etymology

Not until the 16th century did the word "race" enter into the English language, from the French "race" - "race, breed, lineage" (which in turn was probably a loan from the Italian "razza"). Meanings of the term in the 16th century included "wines with a characteristic flavour", "people with common occupation", and "generation". A meaning of "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 (note the continued use of the expression "the human race"). The ultimate origin of the word is unknown; suggestions include Arabic ra'is meaning "head", but also "beginning" or "origin".

Race in ancient civilizations

Given visually 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. For example, the Ancient Egyptian sacred text called Book of Gates identifies four ethnic categories that are now conventionally labeled "Egyptians", "Asiatics", "Libyans", and "Nubians", but such distinctions tended to conflate differences as defined by physical features such as skin tone, with tribal and national identity. Classical civilizations from Rome to China tended to invest much more importance in familial or tribal affiliation than with ones physical appearance (Dikötter 1992; Goldenberg 2003). Ancient Greek and Roman authors also attempted to explain and categorize visible biological differences among 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 became full members of a society by growing up within that society or by adopting that 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.

Age of Discovery

The word "race", along with many of the ideas now associated with the term, were products of European imperialism and colonization during the age of exploration.(Smedley 1999) As Europeans encountered people from different parts of the world, they speculated about the physical, social, and cultural differences among various human groups. The rise of the Atlantic slave trade, which gradually displaced an earlier trade in slaves from throughout the world, created a further incentive to categorize human groups in order to justify the subordination of African slaves.(Meltzer 1993) Drawing on Classical sources and upon their own internal interactions — for example, the hostility between the English and Irish was a powerful influence on early thinking about the differences between people (Takaki 1993) — 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 upon their social structures as was found 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 today in non-colonised countries such as China and Japan.

Scientific concepts of "race"

The first scientific attempts to classify humans by categories of 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

According to philosopher Michel Foucault, theories of both racial and class conflict can be traced to 17th century political debates about innate differences among ethnicities. In England radicals such as John Lilburne emphasised conflicts between Saxon and Norman peoples. In France Henri de Boulainvilliers argued that the Germanic Franks possessed a natural right to leadership, in contrast to descendants of the Gauls. In the 18th century, the differences among 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. It was further argued that some groups may be the result of mixture between formerly distinct populations, but that careful study could 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 Foucault demonstrated in his historical analysis; 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) and Vacher de Lapouge's "anthroposociology", 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 culture as well as by physical appearances (Hannaford 1996). Campaigns of oppression and genocide were often motivated by supposed racial differences (Horowitz 2001).

In Charles Darwin's most controversial book, The Descent of Man, he made strong suggestions of racial differences and European superiority. In Darwin's view, stronger tribes of humans always replaced weaker tribes. As savage tribes came in conflict with civilized nations, such as England, the less advanced people were destroyed. The destruction of the weaker peoples seemed desirable to many scientists at the time. It was thought that "fit" people would replace the "unfit" and human evolution would be accelerated. Nevertheless, he also noted the great difficulty naturalists had in trying to decide how many "races" there actually were (Darwin was himself a monogenist on the question of race, believing that all humans were of the same species and finding "race" to be a somewhat arbitrary distinction among groups):

Man has been studied more carefully than any other animal, and yet there is the greatest possible diversity amongst capable judges whether he should be classed as a single species or race, or as two (Virey), as three (Jacquinot), as four (Kant), five (Blumenbach), six (Buffon), seven (Hunter), eight (Agassiz), eleven (Pickering), fifteen (Bory St. Vincent), sixteen (Desmoulins), twenty-two (Morton), sixty (Crawfurd), or as sixty-three, according to Burke. This diversity of judgment does not prove that the races ought not to be ranked as species, but it shews that they graduate into each other, and that it is hardly possible to discover clear distinctive characters between them.

20th- and 21st-Century debates over race

Systems of categorization preferred depends on scale

Discussions of race, how humans might be divided on an infraspecies basis, are made more complicated because race research has taken place on at least two scales (global and national) and from the point of view of different research aims. Evolutionary scientists are typically interested in humanity as a whole; and taxonomic racial classifications are often either unhelpful to, or refuted by, studies that focus on the question of global human diversity. Policy-makers and applied professions (such as law-enforcement or medicine), however, are typically concerned only with genotypic or phenotypic variation at the national or sub-national scale, and find taxonomic racial categories useful.

These distinctions of research aims and scale can be seen by the example of three major research papers published since 2002: Rosenberg et al. (2002), Serre & Pääbo (2004), and Tang et al. (2005). Both Rosenberg et al. and Serre & Pääbo study global genetic variation, but they arrive at different conclusions. Serre & Pääbo attribute their differing conclusions to experimental design. While Rosenberg et al. studied individuals from populations across the globe without concentrating on particular geographical areas, Serre & Pääbo chose individuals for study from remote and discrete regions. By sampling individuals from major populations on each continent, Rosenberg et al. find evidence for genetic "clusters" (i.e., groupings that might plausibly be equated to earlier races). In contrast, Serre & Pääbo find that with respect to geography human genetic variation is continuous and "clinal," which denies the presumed clear assignability of all individuals to traditional racial categories. The research interest of Rosenberg et al. is medicine (i.e., epidemiology), whereas the research interest of Serre & Pääbo is human evolution. Tang et al. studied genetic variation within the United States with an interest in whether race/ethnicity or geography is of greater utility to epidemiological research. Tang et al. find that race/ethnic membership (or membership in one of the genetic "clusters" of Rosenberg et al.) is of greater utility within the United States that is one's corrent geographical location. Further recent research correlating self-identified race with population genetic structure Structure 2.1 echoed the conclusions in Tang. Indeed, the contrasting conclusions between global and national levels of analysis were predicted by Serre & Pääbo: Template:Quotation Three main components of the U.S. population having been drawn from remote parts of the world, the long clinal bridges between the groups that exist in Eurasia have disappeared and those populations seem rather starkly isolated when examined in their new environment.

Race as subspecies

With the advent of the modern synthesis in the early 20th century, many biologists sought to use evolutionary models and populations genetics to develop more rigorous definitions of "race." An early attempt was to identify races as subspecies (a subspecies is a clearly distinguishable 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 among individuals is noticeable and follows a pattern, but there are no clear dividing lines among separate groups: they fade imperceptibly into one another. Such clinal variation always indicates substantial gene flow among the apparently separate groups that make up the population(s). Populations that have a steady, substantial gene flow among 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 (subspecies, or, in current parlance, two or more sub-types). These are 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. Note that groups that do not interbreed with a high degree of success, even if brought together such that they had the opportunity to do so, are not races: they are separate species.

This attempt at conceptual precision has gained currency with many biologists, especially zoologists and botanists. Many physical anthropologists have concluded that H. sapiens was polytypic in the past (H. sapiens neandertalensis, now extinct, having been a subspecies of H. sapiens). All human beings now alive, however, are regarded as belonging to the same subspecies: Homo sapiens sapiens - in effect, H. sapiens is now monotypic.

Races as clades

By the 1970s many evolutionary scientists were avoiding the concept of "subspecies" as a taxonomic category for four reasons:

• very few data indicate that contiguous subspecies ever become species
• geographically disjunct groups regarded as subspecies usually can be demonstrated to actually be distinct species
• subspecies had been recognized on the basis of only 2-5 phenotypic characters, which often were adaptations to local environments but which did not reflect the evolutionary differentiation of populations as a whole
• with the advent of molecular techniques used to get a better handle on genetic introgression (gene flow), the picture afforded by looking at genetic variation was often at odds with the phenotypic variation (as is the case with looking at genes versus percentage of epidermal melanin in human populations)

These criticisms have coincided with the rise of cladistics

A clade is a taxonomic group of organisms consisting of a single common ancestor and all the descendants of that ancestor. Every creature produced by sexual reproduction has two immediate lineages, one maternal and one paternal. https://www.anthrosource.net/doi/abs/10.1525/an.2006.47.2.7?journalCode. Whereas Carolus Linnaeus established a taxonomy of living organisms based on anatomical similarities and differences, cladistics seeks to establish a taxonomy — the phylogenetic tree — based on genetic similarities and differences and tracing the process of acquisition of multiple characteristics by single organisms. Some researchers have tried to clarify the idea of race by equating it to the biological idea of the clade:

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 migration paths. These single-locus sources of DNA do not recombine and are inherited from a single parent. Individuals from the various continental groups tend to be more similar to one another than to people from other continents, and tracing either mitochondrial DNA or non-recombinant Y-chromosome DNA explains how people in one place may be largely derived from people in some remote location. 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 chimpanzees 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 chimpanzees between four and seven million years ago.

Chimpanzees and humans belong to different genera, indicated in Blue. 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, and the points made in the preceding section, insofar as they apply to an "African race", are understood here). Note that vertical distances are not meaningful in this representation.

Most evolutionary scientists have rejected the identification of races with clades for two reasons. First, as Rachel Caspari (2003) argued, clades are by definition monophyletic groups (a taxon that includes all descendants of a given ancestor) since no groups currently regarded as races are monophyletic, none of those groups can be clades.

For anthropologists Lieberman and Jackson (1995), however, there are more profound methodological and conceptual problems with using cladistics to support concepts of race. They emphasize that "the molecular and biochemical proponents of this model explicitly use racial categories in their initial grouping of samples". For example, the large and highly diverse macroethnic groups of East Indians, North Africans, and Europeans are presumptively grouped as Caucasians prior to the analysis of their DNA variation. This limits and skews interpretations, obscures other lineage relationships, deemphasizes the impact of more immediate clinal environmental factors on genomic diversity, and can cloud our understanding of the true patterns of affinity. They argue that however significant the empirical research, these studies use the term race in conceptually imprecise and careless ways. They suggest that the authors of these studies find support for racial distinctions only because they began by assuming the validity of race.

For empirical reasons we prefer to place emphasis on clinal variation, which recognizes the existence of adaptive human hereditary variation and simultaneously stresses that such variation is not found in packages that can be labeled races.

Indeed, recent research reports evidence for smooth, clinal genetic variation even in regions previously considered racially homogeneous, with the apparent gaps turning out to be artifacts of sampling techniques (Serre & Pääbo 2004). These scientists do not dispute the importance of cladistic research, only its retention of the word race, when reference to populations and clinal gradations are more than adequate to describe the results.

Race and Population Genetics: "population" and "cline" as alternatives

At the beginning of the 20th century, anthropologists questioned, and eventually abandoned, the claim that biologically distinct races are isomorphic with distinct linguistic, cultural, and social groups. Thereafter, 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), 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 animal systematics, and further rejected the claim that "races" were equivalent to "subspecies" (Wilson and Brown 1953).

One of the crucial innovations in reconceptualizing genotypic and phenotypic variation was anthropologist C. Loring Brace's observation that such variations, insofar as it is affected by natural selection, migration, or genetic drift, are distributed along geographic gradations; these gradations are 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—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 among populations, argued that neither "race" nor "subspecies" were appropriate or useful ways to describe populations (Lewontin 1973). Some researchers report the variation between racial groups (measured by Sewall Wright's population structure statistic F_ST) accounts for as little as 5% of human genetic variation². However, critics charge that Lewontin failed to juxtapose the figures properly. They cite at least two errors in Lewontin's calculations: (1) his figure of 85%:15% (within populations genetic variability vs. between populations genetic variability) is simply the average of all the genetic loci on hand, and thus fails to represent the variation at individual loci (for instance, the genetic loci for skin color do not vary 85% between individuals and only 15% between populations). And (2) Lewontin's analysis failed to address the genetic variability within an individual, since humans are diploid organisms, receiving one set of chromosomes from each parent (Sarich and Miele 2004).

A. W. F. Edwards claimed in 2003 that such conclusions are unwarranted because the argument ignores the fact that most of the information that distinguishes populations is hidden in the correlation structure of the data and not simply in the variation of the individual factors"Human genetic diversity: Lewontin's fallacy.", Edwards AW., Gonville and Caius College, Cambridge, in PubMed, 2003 Aug;25(8):798-801.</ref> While if true it would make Lewontin's argument unwarranted, Edward's paper does not address the existence or absence of human races. (See Lewontin's Fallacy.)

Also, it has been argued that the calculation of within group and between group diversity has violated certain expectations regarding human genetic variation. Calculation of this variation is known as F_ST and Long and Kittles (2003) have questioned the validity of this value as a reproducible statistic. The first problem is that effective population size is assumed to be equal in all instances of the calculation of F_ST, but if population sizes vary, then allele relatedness among alleles will also vary. The second problem is that F_ST calculation has assumed that each population is evolutionarily independent. Calculation of F_ST can therefore only be made for the set of populations being observed, and generalisations from specific data sets cannot be applied to the species as a whole.

Long and Kittles tested four models for determining F_ST and concluded that the model used most often for estimating this statistic is the simplest and worst fitting. Their best fit model was still a poor fit for the observed genetic variation, and calculation of F_ST for this model can only be made on a population by population basis. They conclude that African populations have the highest level of genetic diversity, with diversity much reduced in populations outside of Africa. They postulate that if an extra-terrestrial alien life form killed the entire human species, but selected a single population to preserve, the choice of population to keep would greatly effect the level of diversity represented. If an African population were selected then no diversity would be lost, whereas nearly a third of genetic diversity would be lost if a Papuan New Guinea population were chosen. Indeed within population genetic diversity in African populations has been shown to be greater than between population genetic diversity for Asians and Europeans. They conclude that their findings are consistent with the American Association of Physical Anthropologists 1996 statement on race that all human populations derive from a common ancestral group, that there is great genetic diversity within all human populations, and that the geographic pattern of variation is complex and presents no major discontinuity. They also state that none of the race concepts they discuss are compatible with their results.

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).

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—indicates 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 hypothesis 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.Template:Fact 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 proves to be difficult, since such features may have resulted from sexual selection for individuals with certain appearances or from genetic drift (Roseman 2004).

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.)

According to Jonathan Marks,

By the 1970s, it had become clear that (1)most human differences were cultural; (2) what was not cultural was principally polymorphic - that is to say, found in diverse groups of people at different frequencies; (3) what was not cultural or polymorphic was principlally clinal - that is to say, gradually variable over geography; and (4) what was left - the component of human diversity that was not cultural, polymorphic, or clinal - was very small.

A consensus consequently developed among anthropologists and geneticisms that race as the previous generation had known it - as largely discrete, geographically distinct, gene pools - did not exist.

In the face of this rejection of race by evolutionary scientists, many social scientists have replaced the word race with the word "ethnicity" to refer to self-identifying groups based on beliefs concerning shared culture and history. 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 U.S. civil rights movement and the emergence of numerous anti-colonial movements worldwide. They thus came to understood that these justifications, even when expressed in language that sought to appear objective, were social constructs.

Race and models of human evolution

In a recent article, Leonard Lieberman and Fatimah Jackson have called attention to the fact that although the concepts of cline, population, and ethnocity, as well as humanitarian and political concerns, have led many scientists away from the notion of race, a recent survey showed that physical anthropologists were evenly divided as to whether race is a valid biological concept. Noting that among physical anthropologists the vast majority of opposition to the race concept comes from population geneticists, any new support for a biological concept of race will likely come from another source, namely, the study of human evolution. They therefore ask what, if any, implications current models of human evolution may have for any biological conception of race.

Today all humans are classified as belonging to the species Homo sapiens sapiens. However, this is not the first species of hominids: the first species of genus Homo, Homo habilis evolved in East Africa at least 2 million years ago, and members of this species populated different parts of Africa in a relatively short time. Homo erectus evolved more than 1.8 million years ago, and by 1.5 million years ago had spread throughout the Old World. Virtualy all physical anthropologists agree that Homo sapiens evolved out of Homo erectus. Anthropologists have been divided as to whether Homo sapiens evolved independently (and more or less simultaneously) out of different populations of H. erectus in different parts of the world (called the Multiregional Model, or the Regional Continuity Model), or evolved only in East Africa, and then migrated out of Africa and replaced H. erectus populations throughout the Old World (called the Out of Africa Model or the Complete Replacement Model). Anthropologists contine to debate both possibilities, although there is considerably more support for the Out of Africa Model.

The multiregional model

The multi-regional hypothesis consists of several models of human evolution that all posit that the human races evolved from separate populations of H. erectus over the past million years. Carleton Coon, an early advocate of this model, suggested that the independent evolution of H. sapiens in different parts of the world accounts for the existence of geographically and genetically distinct races - in short, that multiregional evolution was tantamount to multiracial evolution, the simultaneous but independent evolution of different races Current advocates of this model, primarily Milford Wolpof and his associates, have argued that the simultaneous evolution of H. sapiens in different parts of Europe and Asia would have been possible only if there was a degree of gene flow between archaic populations, and have rejected Coon's idea of multiracial evolution. Frayer et al. (1993) 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 of phenotypic variation (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 argued that the multiregional model nevertheless depends on several assumptions — (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 — each of which "implies a greater degree of racial differentiation than does the Out-of-Africa displacement model." Against these assumptions, they argue that 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, and do not necessarily support the multi-regional model.

The out of Africa model

Archaic H. sapiens are believed by some to have evolved 400,000 to 600,000 years ago. According to the Out of Africa Model, developed by Christopher Stringer and Peter Andrews, modern H. sapiens evolved in Africa 200,000 years ago and then migrated to Europe and Asia, where it replaced existing hominid species. This time scale — considerably less than the million years for geographically separate human evolution posited by the Multiregional Model — leaves less time for genetic divergence among human populations, and thus suggests that humans around the world are more closely related than the Multiregional model would suggest. The Out of Africa Model has gained support by recent, though controversial, research by molecular biologists working with mitochondrial DNA (mtDNA) (this is DNA found in the cytoplasm, rather than nucleus, of cells). Cann et. al. argue that mtDNA mutates at a faster rate than nuclear DNA and thus facilitates the study of human diversity; moreover, it is inherited solely from the mother and does not recombine, so "it is a tool for relating individuals to one another." Working with a sample of 145 placentas taken from individuals from five geographic regions (Sub-Saharan Africa, Asia, "Caucasians" – North Africa, Europe and the Middle East – aboriginal Australians and Aboriginal New Guineans), they constructed a tree representing relations among 133 different types of mtDNA, and argued that the tree is "a genealogy linking maternal lineages in modern human beings to a common ancestral female. After assessing different trees (i.e. different ways of organizing the results) they reached two significant conclusions: first, that all were descended from a woman from Africa, i.e. that humans evolved in Africa (supporting the Out of Africa model). Second, they concluded that each non-African population had multiple origins, representing different lineages. Based on known figures for the rate of mtDNA mutation, Cann et. al. calculated that modern Humans may have left Africa during one of two periods: 90,000-180,000 years ago, or 23,000-105,000 years ago. Moreover, humans colonized Australia 40,000 years ago, New Guinea 30,000 years ago, and the New World 12,000 years ago. According to Lieberman and Jackson, the Out of Africa Model has several implications for any understanding of races as biological phenomena. First, "the shallow time dimensions minimize the degree to which racial differences could have evolved." Second, it does present a major distinction between African and Eurasian groups, which "could be used to emphasize biological differences, and thereby provide support for the race concept." They also observe that "racial stratification is used for initial grouping, and inherent bias is introduced from the very beginning of data collection and interpretation.

Comparison of the two models

Lieberman and Jackson have argued that while advocates of both the Multiregional Model and the Out of Africa Model use the word race and make racial assumptions, none define the term. They conclude that "Each model has implications that both magnify and minimize the differences between races. yet each model seems to take race and races as a conceptual reality. The net result is that those anthropologists who prefer to view races as a reality are encouraged to do so" and conclude that students of human evolution would be better off avoiding the word race, and instead describe genetic differences in terms of populations and clinal gradations.

Race as lineage

Work by molecular biologists such as Cann et. al. on mtDNA has led some scientists, such as Johnson et. al., to a new definition of race as lineage; after constructing a phylogeny of mtDNA types, Johnson et. al. suggested that "the three central types are among those most likely to have been present prior to the formation of the extant human races".. Although most molecular biologists avoid making, or question, using this data to support racial classifications, this view has gained some traction among research in biomedicine, such as Risch et. al. and Burchard et. al.

In the case of mtDNA research, lineages consist of people descended from one female ancestor.Template:Fact This work is being supplemented by recent research by molecular biologists studying the human genome. With a genome of approximate 3 billion nucleotides, on average two humans differ at approximately 3 million nucleotides. Some of these single nucleotide polymorphisms (SNPs) are functional and influence the phenotypic differences between humans, which means that they are also subject to natural selection. Nowever, most of these SNPs are neutral, meaning they do not express themselves phenotypically and are not subject to natural selection (see International HapMap Project). Because this so-called "junk DNA" is not subject to natural selection, it changes very little over the generations. Consequently, scientists can use the distribution of neutral polymorphisms among contemporary humans to map additional "lineages" (in the case of nuclear DNA, descent from an apical male ancestor). The result has been a new industry in which individuals can send genetic samples to laboratories that identify the person's Y chromosome or mtDNA lineage, popularized by scientists such as Spencer Wells.

Genetic data can be used to infer population structure and assign individuals to groups that often correspond with their self-identified geographical ancestry. Recently, Lynn Jorde and Steven Wooding argued that "Analysis of many loci now yields reasonably accurate estimates of genetic similarity among individuals, rather than populations. Clustering of individuals is correlated with geographic origin or ancestry."

The inference of population structure from multilocus genotyping depends on the selection of a large number of informative genetic markers. These studies usually find that groups of humans living on the same continent are more similar to one another than to groups living on different continents. Many such studies are criticized for assigning group identity a priori. However, even if group identity is stripped and group identity assigned a posteriori using only genetic data, population structure can still be inferred. For example, using 377 markers, Rosenberg et al. (2002) were able to assign 1,056 individuals from 52 populations around the globe to one of six genetic clusters, of which five correspond to major geographic regions.

Genetic techniques that distinguish clustering between continents can also be used to describe clustering within continents. However, the study of intra-continental ancestry may require a greater number of informative markers. Indigenous populations from neighboring geographic regions on average share more recent common ancestors. As a result, allele frequencies will be correlated between these groups. This phenomenon is often seen as a cline of allele frequencies. The existence of allelic clines has been offered as evidence that individuals cannot be allocated into genetic clusters (Kittles & Weiss 2003). However, others argue that low levels of differentiation between groups merely make the assignment to groups more difficult, not impossible (Bamshad et al. 2004). Also, clines and clusters, seemingly discordant perspectives on human genetic diversity may be reconciled. A recent comprehensive study has stated: "At the same time, we find that human genetic diversity consists not only of clines, but also of clusters." Such 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".Template:Fact Genetic lineages have in common with older notions of race the idea of biological relatedness.Template:Fact Unlike older notions of race, however, they are not connected to claims about human behavior or character. Nadia Abu el-Haj has thus argued that "postgenomics does seem to be giving race a new lease on life." Nevertheless, Abu el-Haj argues that in order to understand what it means to think of race in terms of genetic lineages, one must understand that

Race science was never just about classification. It presupposed a distinctive relationship between "nature" and "culture," understanding the differences in the former to ground and to generate the different kinds of persons ("natural kinds") and the distinctive stages of cultures and civilizations that inhabit the world.

Abu el-Haj argues that genomics and the mapping of lineages based on junk DNA liberates "the new racial science from the older one by disentangling ancestry from culture and capacity." As an example, she refers to recent work by Hammer et. al., which aimed to test the claim that present-day Jews are more closely related to one another than to neighboring non-Jewish populations. Hammer et. al found that the degree of genetic similarity among Jews shifted depending on the locus investigated, and suggested that this was the result of natural selection acting on particular locii. They therefore focused on the nonrecombining Y chromosome to "circumvent some of the complications associeted with selection" . As another example she points to work by Thomas et. al., who sought to distinguish between the Y chromosomes of Jewish priests (in Judaism, membership in the priesthood is passed on through the father's line) and the Y chromosomes of non-Jews.Abu el-Haj concluded that this new "race science" calls attention to the importance of "ancestry" (narrowly defined, as it does not include all ancestors) in some relgions and in popular culture, and peoples' desire to use science to confirm their claims about ancestry; this "race science," she argues is fundamentally different from older notions of race that were used to explain differences in human behavior or social status:

As neutral markers, [junk DNA] cannot generate cultural, behavioral, or, for that matter, truly biological differences between groups .... mtDNA and Y-chromosome markers relied on in such work are not "traits" or "qualities" in the old racial sense. They do not render some populations more prone to violence, more likely to suffer psychiatric disorders, or for that matter, incapable of being fully integrated - because of their lower evolutionary development - into a European cultural world. Instead, they are "marks," signs of religious beliefs and practices .... it is via biological noncoding genetic evidence that one can demonstrate that history itself is shared, that historical traditions are (or might well be) true."

The question is, how highly do genetic lineages correlate with self-identified races? Scientists are divided. Some 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/ethnicity (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 U.S. population.

However, in analyses that assign individuals to groups it becomes less apparent that self-described racial groups are reliable indicators of ancestry. One cause of the reduced power of the assignment of individuals to groups is admixture. Some racial or ethnic groups, especially Hispanic groups, do not have homogenous ancestry. For example, self-described African Americans tend to have a mix of West African and European ancestry. Shriver et al. (2003) found that on average African Americans have ~80% African ancestry. Also, in a survey of college students who self-identified as “white” in a northeastern U.S. university, ~30% of whites had less than 90% European ancestry.

Moreover, many have criticized this notion of lineage which is based on the identification of one male or one female apical ancestor at the time of a population bottleneck,Template:Fact while disregarding (because unavailable using genomic technology) countless other ancestors every individual has and shares with others, including people of different "lineages." Charles Rotimi, of Howard University's National Human Genome center, has highlighted the methodological flaws in research — that "the nature or appearance of genetic clustering (grouping) of people is a function of how populations are sampled, of how criteria for boundaries between clusters are set, and of the level of resolution used" all bias the results — and concluded that people should be very cautious about relating genetic lineages to their own sense of identity. Moreover, Stephan Palmie has responded to Abu el-Haj's claim that genetic lineages make possible a new, politically, economically, and socially benign notion of race and racial difference by suggesting that efforts to link genetic history and personal identity will inevitably "ground present social arrangements in a time-hallowed past," that is, use biology to explain cultural differences and social inequalities.

Summary of different definitions of race

|- | Essentialist || Hooton (1926) || "A great division of mankind, characterized as a group by the sharing of a certain combination of features, which have been derived from their common descent, and constitute a vague physical background, usually more or less obscured by individual variations, and realized best in a composite picture." |- | Taxonomic || Mayr (1969) || "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." |- | Clade || Levin (2002) || Race "connotes geographic ancestry, by continent or large continental subregion" and "is used to denote continental or subcontinental clades". In "Cladistic taxonomy ... the basic taxon [is] the genealogical unit, ancestors-plus-line- (or tree) -of-descent, what according to the present analysis races are." |- | Population || Dobzhansky (1970) || "Races are genetically distinct Mendelian populations. They are neither individuals nor particular genotypes, they consist of individuals who differ genetically among themselves." |- | Lineage || Templeton (1998) || "A subspecies (race) is a distinct evolutionary lineage within a species. This definition requires that a subspecies be genetically differentiated due to barriers to genetic exchange that have persisted for long periods of time; that is, the subspecies must have historical continuity in addition to current genetic differentiation." |}

Current views 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 within some fields, such as biology, there is strong consensus. Some studies use the word race in its early essentialist taxonomic sense. Many others still use the term race, but use it to mean a population, clade, or haplogroup. Others eschew the concept of race altogether, and use the concept of population as a less problematical unit of analysis.

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 was largely rejected by the community of social sciences in the second half of the 20th century.

Scientific support for the Caucasoid, Negroid, Mongoloid terminology of racial classification has diminished over the past century. These terms originally denoted skull types and sprang from the technique known as craniofacial anthropometry, but these disciplines have been abandoned by the mainstream scientific community. Today they have only two common uses. They are used in forensic anthropology as an indicator of ethnicity of skeletal remains. And they can be used as euphemisms for making racially based distinctions that are now regarded as being racist and baseless by mainstream culture.

Since 1932, some 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. According to one academic journal entry, where 78 percent of the articles in the 1931 Journal of Physical Anthropology employed these or nearly synonymous terms reflecting a bio-race paradigm, only 36 percent did so in 1965, and just 28 percent did in 1996. 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".

In an ongoing debate, some geneticists argue that race is neither a meaningful concept nor a useful heuristic device, and even that genetic differences among groups are biologically meaningless, on the grounds that more genetic variation exists within such races than among them, and that racial traits overlap without discrete boundaries. Other geneticists, in contrast, argue that categories of self-identified race/ethnicity or biogeographic ancestry are both valid and useful, that these categories correspond with clusters inferred from multilocus genetic data, and that this correspondence implies that genetic factors might contribute to unexplained phenotypic variation between groups.

In February, 2001, the editors of the medical journal Archives of Pediatrics and Adolescent Medicine asked authors to no longer use "race" as an explanatory variable and not to use obsolescent terms. Some other peer-reviewed journals, such as the New England Journal of Medicine and the American Journal of Public Health, have made similar endeavours. Furthermore, the National Institutes of Health recently issued a program announcement for grant applications through February 1, 2006, specifically seeking researchers who can investigate and publicize among primary care physicians the detrimental effects on the nation's health of the practice of medical racial profiling using such terms. The program announcement quoted the editors of one journal as saying that, "analysis by race and ethnicity has become an analytical knee-jerk reflex."

A survey, taken in 1985 (Lieberman et al. 1992), asked 1,200 anthropologists how many disagree with the following proposition: "There are biological races in the species Homo sapiens." The responses were:

• physical anthropologists 41%
• cultural anthropologists 53%

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 (although it did clearly specify biological race within the species Homo Sapiens); it is difficult to say whether those who supported the statement thought of race in taxonomic or population terms.

The same survey, taken in 1999 , showed the following changing results for anthropologists:

• physical anthropologists 69%
• cultural anthropologists 80%

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