Scientists Call for End to Race Denial: Let's celebrate human genetic diversity
Bruce Lahn and Lanny Ebenstein | Nature | 8 October 2009
Science is finding evidence of genetic diversity among groups of people as well as among individuals. This discovery should be embraced, not feared, say Bruce T. Lahn and Lanny Ebenstein.
A growing body of data is revealing the nature of human genetic diversity at increasingly finer resolution. It is now recognized that despite the high degree of genetic similarities that bind humanity together as a species, considerable diversity exists at both individual and group levels (see box, page 728). The biological significance of these variations remains to be explored fully. But enough evidence has come to the fore to warrant the question: what if scientific data ultimately demonstrate that genetically based biological variation exists at non-trivial levels not only among individuals but also among groups? In our view, the scientific community and society at large are ill-prepared for such a possibility. We need a moral response to this question that is robust irrespective of what research uncovers about human diversity. Here, we argue for the moral position that genetic diversity, from within or among groups, should be embraced and celebrated as one of humanity's chief assets.
The current moral position is a sort of 'biological egalitarianism'. This dominant position emerged in recent decades largely to correct grave historical injustices, including genocide, that were committed with the support of pseudoscientific understandings of group diversity. The racial-hygiene theory promoted by German geneticists Fritz Lenz, Eugene Fischer and others during the Nazi era is one notorious example of such pseudoscience. Biological egalitarianism is the view that no or almost no meaningful genetically based biological differences exist among human groups, with the exception of a few superficial traits such as skin colour. Proponents of this view seem to hope that, by promoting biological sameness, discrimination against groups or individuals will become groundless.
We believe that this position, although well intentioned, is illogical and even dangerous, as it implies that if significant group diversity were established, discrimination might thereby be justified. We reject this position. Equality of opportunity and respect for human dignity should be humankind's common aspirations, notwithstanding human differences no matter how big or small. We also think that biological egalitarianism may not remain viable in light of the growing body of empirical data.
Many people may acknowledge the possibility of genetic diversity at the group level, but see it as a threat to social cohesion. Some scholars have even called for a halt to research into the topic or sensitive aspects of it, because of potential misuse of the information. Others will ask: if information on group diversity can be misused, why not just focus on individual differences and ignore any group variation? We strongly affirm that society must guard vigilantly against any misuse of genetic information, but we also believe that the best defence is to take a positive attitude towards diversity, including that at the group level. We argue for our position from two perspectives: first, that the understanding of group diversity can benefit research and medicine, and second, that human genetic diversity as a whole, including group diversity, greatly enriches our species.
Box 2. Emerging understanding of human genetic diversity
Genetic diversity is the differences in DNA sequence among members of a species. It is present in all species owing to the interplay of mutation, genetic drift, selection and population structure. When a species is reproductively isolated into multiple groups by geography or other means, the groups differentiate over time in their average genetic make-up.
Anatomically modern humans first appeared in eastern Africa about 200,000 years ago. Some members migrated out of Africa by 50,000 years ago to populate Asia, Australia, Europe and eventually the Americas. During this period, geographic barriers separated humanity into several major groups, largely along continental lines, which greatly reduced gene flow among them. Geographic and cultural barriers also existed within major groups, although to lesser degrees.
This history of human demography, along with selection, has resulted in complex patterns of genetic diversity. The basic unit of this diversity is polymorphisms — specific sites in the genome that exist in multiple variant forms (or alleles). Many polymorphisms involve just one or a few nucleotides, but some may involve large segments of genetic material. The presence of polymorphisms leads to genetic diversity at the individual level such that no two people's DNA is the same, except identical twins. The alleles of some polymorphisms are also found in significantly different frequencies among geographic groups. An extreme example is the pigmentation gene SLC24A5. An allele of SLC24A5 that contributes to light pigmentation is present in almost all Europeans but is nearly absent in east Asians and Africans.
Given these geographically differentiated polymorphisms, it is possible to group humans on the basis of their genetic make-up. Such grouping largely confirms historical separation of global populations by geography. Indeed, a person's major geographic group identity can be assigned with near certainty on the basis of his or her DNA alone (now an accepted practice in forensics). There is growing evidence that some of the geographically differentiated polymorphisms are functional, meaning that they can lead to different biological outcomes (just how many is the subject of ongoing research). These polymorphisms can affect traits such as pigmentation, dietary adaptation and pathogen resistance (where evidence is rather convincing), and metabolism, physical development and brain biology (where evidence is more preliminary).
For most biological traits, genetically based differentiation among groups is probably negligible compared with the variation within the group. For other traits, such as pigmentation and lactose intolerance, differences among groups are so substantial that the trait displays an inter-group difference that is non-trivial compared with the variance within groups, and the extreme end of a trait may be significantly over-represented in a group.
Several studies have shown that many genes in the human genome may have undergone recent episodes of positive selection — that is, selection for advantageous biological traits. This is contrary to the position advocated by some scholars that humans effectively stopped evolving 50,000–40,000 years ago. In general, positive selection can increase the prevalence of functional polymorphisms and create geographic differentiation of allele frequencies.
» » » » [Racial Reality :: Nature Abstract :: Box 2]
Biologists Take Definitive Stance in 'Race Debate'
Categorization of humans in biomedical research: genes, race and disease
Neil Risch, Esteban Burchard, Elad Ziv, and Hua Tang | Genome Biology, 2002
With this as background, it is not surprising that numerous human population genetic studies have come to the identical conclusion - that genetic differentiation is greatest when defined on a continental basis. The results are the same irrespective of the type of genetic markers employed, be they classical systems , restriction fragment length polymorphisms (RFLPs) , microsatellites [7,8,9,10,11], or single nucleotide polymorphisms (SNPs) . For example, studying 14 indigenous populations from 5 continents with 30 microsatellite loci, Bowcock et al.  observed that the 14 populations clustered into the five continental groups, as depicted in Figure 1. The African branch included three sub-Saharan populations, CAR pygmies, Zaire pygmies, and the Lisongo; the Caucasian branch included Northern Europeans and Northern Italians; the Pacific Islander branch included Melanesians, New Guineans and Australians; the East Asian branch included Chinese, Japanese and Cambodians; and the Native American branch included Mayans from Mexico and the Surui and Karitiana from the Amazon basin. The identical diagram has since been derived by others, using a similar or greater number of microsatellite markers and individuals [8,9]. More recently, a survey of 3,899 SNPs in 313 genes based on US populations (Caucasians, African-Americans, Asians and Hispanics) once again provided distinct and non-overlapping clustering of the Caucasian, African-American and Asian samples : "The results confirmed the integrity of the self-described ancestry of these individuals". Hispanics, who represent a recently admixed group between Native American, Caucasian and African, did not form a distinct subgroup, but clustered variously with the other groups. A previous cluster analysis based on a much smaller number of SNPs led to a similar conclusion: "A tree relating 144 individuals from 12 human groups of Africa, Asia, Europe and Oceania, inferred from an average of 75 DNA polymorphisms/individual, is remarkable in that most individuals cluster with other members of their regional group" . Effectively, these population genetic studies have recapitulated the classical definition of races based on continental ancestry - namely African, Caucasian (Europe and Middle East), Asian, Pacific Islander (for example, Australian, New Guinean and Melanesian), and Native American.
Populations that exist at the boundaries of these continental divisions are sometimes the most difficult to categorize simply. For example, east African groups, such as Ethiopians and Somalis, have great genetic resemblance to Caucasians and are clearly intermediate between sub-Saharan Africans and Caucasians . The existence of such intermediate groups should not, however, overshadow the fact that the greatest genetic structure that exists in the human population occurs at the racial level.
Most recently, Wilson et al.  studied 354 individuals from 8 populations deriving from Africa (Bantus, Afro-Caribbeans and Ethiopians), Europe/Mideast (Norwegians, Ashkenazi Jews and Armenians), Asia (Chinese) and Pacific Islands (Papua New Guineans). Their study was based on cluster analysis using 39 microsatellite loci. Consistent with previous studies, they obtained evidence of four clusters representing the major continental (racial) divisions described above as African, Caucasian, Asian, and Pacific Islander. The one population in their analysis that was seemingly not clearly classified on continental grounds was the Ethiopians, who clustered more into the Caucasian group. But it is known that African populations with close contact with Middle East populations, including Ethiopians and North Africans, have had significant admixture from Middle Eastern (Caucasian) groups, and are thus more closely related to Caucasians . Furthermore, the analysis by Wilson et al.  did not detect subgroups within the four major racial clusters (for example, it did not separate the Norwegians, Ashkenazi Jews and Armenians among the Caucasian cluster), despite known genetic differences among them. The reason is clearly that these differences are not as great as those between races and are insufficient, with the amount of data provided, to distinguish these subgroups.
Are racial differences merely cosmetic?
Two arguments against racial categorization as defined above are firstly that race has no biological basis [1,3], and secondly that there are racial differences but they are merely cosmetic, reflecting superficial characteristics such as skin color and facial features that involve a very small number of genetic loci that were selected historically; these superficial differences do not reflect any additional genetic distinctiveness . A response to the first of these points depends on the definition of 'biological'. If biological is defined as genetic then, as detailed above, a decade or more of population genetics research has documented genetic, and therefore biological, differentiation among the races. This conclusion was most recently reinforced by the analysis of Wilson et al. . If biological is defined by susceptibility to, and natural history of, a chronic disease, then again numerous studies over past decades have documented biological differences among the races. In this context, it is difficult to imagine that such differences are not meaningful. Indeed, it is difficult to conceive of a definition of 'biological' that does not lead to racial differentiation, except perhaps one as extreme as speciation.
A forceful presentation of the second point - that racial differences are merely cosmetic - was given recently in an editorial in the New England Journal of Medicine : "Such research mistakenly assumes an inherent biological difference between black-skinned and white-skinned people. It falls into error by attributing a complex physiological or clinical phenomenon to arbitrary aspects of external appearance. It is implausible that the few genes that account for such outward characteristics could be meaningfully linked to multigenic diseases such as diabetes mellitus or to the intricacies of the therapeutic effect of a drug." The logical flaw in this argument is the assumption that the blacks and whites in the referenced study differ only in skin pigment. Racial categorizations have never been based on skin pigment, but on indigenous continent of origin. For example, none of the population genetic studies cited above, including the study of Wilson et al. , used skin pigment of the study subjects, or genetic loci related to skin pigment, as predictive variables. Yet the various racial groups were easily distinguishable on the basis of even a modest number of random genetic markers; furthermore, categorization is extremely resistant to variation according to the type of markers used (for example, RFLPs, microsatellites or SNPs).
Genetic differentiation among the races has also led to some variation in pigmentation across races, but considerable variation within races remains, and there is substantial overlap for this feature. For example, it would be difficult to distinguish most Caucasians and Asians on the basis of skin pigment alone, yet they are easily distinguished by genetic markers. The author of the above statement  is in error to assume that the only genetic differences between races, which may differ on average in pigmentation, are for the genes that determine pigmentation.
» » » » [NIH, via Racial Reality]
AAA Statement on Race
December 7, 2005 | American Anthropoligical Association
In 1998, the American Anthropological Association issued an official statement declaring that clearly demarcated, biological races don't exist, which is supposed to represent "the contemporary thinking and scholarly positions of a majority of anthropologists". This irresponsible exercise in PC pandering is constantly cited by uninformed people looking to discredit the reality of race.
Here are the three main flaws with the statement:
1) All but the first two paragraphs discuss social aspects of race (i.e. racism), going into detail about racial pseudo-theories and discrimination from colonial times to the Holocaust. It's interesting but it doesn't belong in a statement regarding the scientific aspects of race.
2) The brief paragraph that actually deals with anthropology emphasizes the overlapping across biological populations of single, adaptive traits like skin color and hair form, but it makes no mention whatsoever of skeletal structure and its uses in determining racial affinity in the field of forensic anthropology.
3) The other scientifically oriented paragraph delves into population genetics (not the AAA's field) to argue that large within-group variation renders any between-group variation meaningless. This may have seemed true back in the 70s when the field was still in its infancy, but today it's rejected as Lewontin's fallacy:In popular articles that play down the genetical differences among human populations, it is often stated that about 85% of the total genetical variation is due to individual differences within populations and only 15% to differences between populations or ethnic groups. It has therefore been proposed that the division of Homo sapiens into these groups is not justified by the genetic data. This conclusion, due to R.C. Lewontin in 1972, is 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.
There is nothing wrong with Lewontin's statistical analysis of variation, only with the belief that it is relevant to classification. It is not true that "racial classification is...of virtually no genetic or taxonomic significance". It is not true, as Nature claimed, that "two random individuals from any one group are almost as different as any two random individuals from the entire world", and it is not true, as the New Scientist claimed, that "two individuals are different because they are individuals, not because they belong to different races" and that "you can't predict someone's race by their genes". Such statements might only be true if all the characters studied were independent, which they are not.
This article could, and perhaps should, have been written soon after 1974. Since then many advances have been made in both gene technology and statistical computing that have facilitated the study of population differences from genetic data. The magisterial book of Cavalli-Sforza, Menozzi and Piazza (13) took the human story up to 1994, and since then many studies have amply confirmed the validity of the approach. Very recent studies (14,15) have treated individuals in the same way that Cavalli-Sforza and Edwards treated populations in 1963, namely by subjecting their genetic information to a cluster analysis thus revealing genetic affinities that have unsurprising geographic, linguistic and cultural parallels. As the authors of the most extensive of these (15) comment, "it was only in the accumulation of small allele-frequency differences across many loci that population structure was identified."
Here's a collection of recent genetic studies that have identified racial clusters:
- Wilson et al. (2001)
- Calo et al. (2001)
- Rosenberg et al. (2002)
- Hua Tang et al. (2005)
- Nan Yang et al. (2005)
- Agrawal et al. (2005)
» » » » [Racial Reality]