Tag Archives: race

On the Concept of Biological Race and Its Applicability to Humans

On the Concept of Biological Race and Its Applicability to Humans
Kaplan, Jonathan and Pigliucci, Massimo (2002)

Abstract
Biological research on race has often been seen as motivated by or lending credence to underlying racist attitudes; in part for this reason, recently philosophers and biologists have gone through great pains to essentially deny the existence of biological human races. We argue that human races, in the biological sense of local populations adapted to particular environments, do in fact exist; such races are best understood through the common ecological concept of ecotypes. However, human ecotypic races do not in general correspond with `folk` racial categories, largely because many similar ecotypes have multiple independent origins. Consequently, while human natural races exist, they have little or nothing in common with `folk` races.

A paper from 2002 that I hadn’t read until today. Yet another nail in the coffin of  ‘genetics has proved there’s no such thing as race’.  I kind of skimmed it (ashamed), but these sections leapt out at me:

Lewontin and Gould have made much of the fact that there is relatively little genetic variation in Homo sapiens (compared at least to other mammals; see Templeton 1999) and that most of what genetic diversity is known to exist within Homo sapiens exists within (rather than between) local populations (see, for example, Gould 1996; Lewontin et al. 1984), and these facts are cited repeatedly in arguments concluding that there are no biologically significant human races. But the idea that this data might imply something about the existence of biologically significant human races emerges from a focus on the wrong sort of biological races.

The question is not whether there are significant levels of between-population genetic variation overall, but whether there is variation in genes associated with significant adaptive  differences between populations (see our discussion in Kaplan and Pigliucci 2001).

But while skin color is not well correlated with other phenotypic traits of interest in humans, there is, despite Gould’s claims (Gould 1996) to the contrary, no guarantee that particular populations of humans will not, due to particular features of their environment, share particular distributions of adaptive behavioral (including intellectual) traits, as opposed to simple physical traits. To the best of our knowledge, there is no evidence that such populations exist, nor are there reasons to suppose that such populations must exist.

I’ve notice that on the no-race side of the fence, they constantly focus on genotypic variation, which is a bit of a red herring as it is phenotypic variation that really defines a race or sub species. Which is more or less what this essay points out.

We aren’t all the same- science is finding evidence of genetic diversity between populations as well as between individuals

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. 

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 certaintly 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. 

A news worthy article, that won’t probably get the attention it deserves in the general media. I’ve noticed over the past few years more and more papers are being published along these lines, and I’d just like to applaud them for having the courage to put this in print, as this kind of published work (observing what are essentially racial differences) can really endanger your career. Most notable was this …

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

Which really goes counter to what it generally presented to the public in those cosy channel four and BBC documentaries like ‘In the blood’  and ‘ Race, the last taboo’. Prof. Jones will not be a happy man when he reads this. Also worthy of attention was this (condensed, it’s in the text as a whole) …

Biological egalitarianism is the view that no or almost no meaningful genetically based biological differences exist among human groups …..We believe that this position, although well intentioned, is illogical and even dangerous…We also think that biological egalitarianism may not remain viable in light of the growing body of empirical data.

So there you go. We aren’t all the same. I’ve believed for the past seven years, ever since I started to show a deeper interest in anthropology and genetics, the ‘no such thing as race’ paradigm was driven by (well meant) egalitarianism ideology and not fact. If there’s no such thing as race, there can’t be racial differences and, ergo, no racism. I think that Lahn’s and Ebenstein’s hopes for a grown up acceptance of between-group differences may be unfulfilled, as the average human just isn’t that reasonable.

Just a Niel Risch paper on population genetics.

Categorization of humans in biomedical research: genes, race and disease
Neil Risch,1,2 Esteban Burchard,3 Elad Ziv,3 and Hua Tang4

A debate has arisen regarding the validity of racial/ethnic categories for biomedical and genetic research. Some claim ‘no biological basis for race’ while others advocate a ‘race-neutral’ approach, using genetic clustering rather than self-identified ethnicity for human genetic categorization. We provide an epidemiologicperspective on the issue of human categorization in biomedical and genetic research that strongly supports the continued use of self-identified race and ethnicity.

 A major discussion has arisen recently regarding optimalstrategies for categorizing humans, especially in the United States, for the purpose of biomedical research, both etiologic and pharmaceutical. Clearly it is important to know whether particular individuals within the population are more susceptible to particular diseases or most likely to benefit from certain therapeutic interventions. The focus of the dialogue has been the relative merit of the concept of ‘race’ or ‘ethnicity’, especially from the genetic perspective. For example, a recent editorialin the New England Journal of Medicine [1] claimed that “race is biologically meaningless” and warned that “instruction in medicalgenetics should emphasize the fallacy of race as a scientific concept and the dangers inherent in practicing race-based medicine.” In support of this perspective, a recent article in Nature Genetics [2] purported to find that “commonly used ethnic labels are both insufficient and inaccurate representations of inferred genetic clusters.” Furthermore, a supporting editorial in the same issue [3] concluded that “population clusters identified by genotype analysis seem to be more informative than those identified by skin color or self-declaration of ‘race’.” These conclusions seem consistent with the claim that “there is no biological basis for ‘race'” [3] and that “the myth of major genetic differences across ‘races’ is nonetheless worth dismissing with genetic evidence” [4]. Of course, the use of the term “major” leaves the door open for possible differences but a priorilimits any potential significance of such differences.

In our view, much of this discussion does not derive from an objective scientific perspective. This is understandable, given both historic and current inequities based on perceived racial or ethnic identities, both in the US and around the world, and the resulting sensitivities in such debates. Nonetheless, we demonstrate here that from both an objective and scientific (genetic and epidemiologic) perspective there is great validity in racial/ethnic self-categorizations, both from the research and public policy points of view.

An interesting read, one that rather disproves the idea that genetics proves race is a social construct. but the real interesting bit to me was..

 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 [5]. 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. [2] 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 [14].

 … because I’m interested in Ethiopian DNA. Which backs up the use of the Mt DNA/Y DNA as genetic markers to measure racial admixture in populations, showing Ethiopians to be almost half Arab, essentially.

If anyone is suspicious of Dr Risch’s motives, he makes quite clear that his main concern is that a race/colour blind approach to medicine is that minority health-care will suffer.

Thus, results from such studies would be largely derived from the Caucasian majority, with obtained parameter estimates that might not apply to the groups with minority representation.

And quite right too. I had an accusation of a neo-Nazi eugenics motive thrown at a study of racial differences in gestation length who’s sole purpose was to lower the mortality rate of black and Asian babies in the UK.

Recognising racial differences saves lives.

Ancient Egyptian population clustering from Loring Brace.

From this C Loring Brace study, Clines and Clusters Versus “Race:” A Test in Ancient Egypt and the Case of a Death on the Nile., dated 1993.

ABSTRACT

The biological affinities of the ancient Egyptians were tested against their neighbors and selected prehistoric groups as well as against samples representing the major geographic population clusters of
the world. Two dozen craniofacial measurements were taken on each individual used. The raw measurements were converted into C scores and used to produce Euclidean distance dendrograms. The measurements were principally of adaptively trivial traits that display patterns of regional similarities
based solely on genetic relationships. The Predynastic of Upper Egypt and the Late Dynastic of Lower Egypt are more closely related to each other than to any other population. As a whole, they show ties with the European Neolithic, North Africa, modern Europe, and, more remotely, India, but not at all with sub-Saharan Africa, eastern Asia, Oceania, or the New World.

Adjacent people in the Nile valley show similarities in trivial traits in an unbroken series from the delta in the north southward through Nubia and all the way to Somalia at the equator. At the same time, the gradient in skin color and body proportions suggests long-term adaptive response to selective forces appropriate to the latitude where they occur. An assessment of “race” is as useless as it is impossible. Neither clines nor clusters alone suffice to deal with the biological nature of a widely distributed population. Both must be used. We conclude that the Egyptians have been in place since back in the Pleistocene and have been largely unaffected by either invasions or migrations. (!?) As others have noted, Egyptians are Egyptians, and they were so in the past as well.

And here are some of the diagrams from this study.

Fig. 2. A Euclidean Distance dendrogram based on C scores providing a picture of the relationships
between samples ranging from the Nile delta up through Nubia to Somalia and samples representing
the eight major regional clusters of the world.

Fig. 3. Euclidean distance dendrogram based on C scores for the constituent subsamples of the African
and Indian (South Asian) regional clusters compared with samples from Bronze Age Jericho and up the
Nile valley to Somalia. The Nubian sample in Figure 2 is broken down into constituent Bronze Age,
Early, and Medieval Christian subsamples.

Fig. 3. Euclidean distance dendrogram based on C scores for the constituent subsamples of the African
and Indian (South Asian) regional clusters compared with samples from Bronze Age Jericho and up the
Nile valley to Somalia. The Nubian sample in Figure 2 is broken down into constituent Bronze Age,
Early, and Medieval Christian subsamples.

Interestingly, this rather contradicts the Keita study  of Predynastic Badarians. This is unsurprising, as the Keita methodology had some major flaws and inaccuracies in it, not least the use of Northern Europeans as the norm for Caucasians, and omitting North African Caucasians as a base line for comparison. It also erroneously describes Predynastic hair as 80% Negroid, when the actual Strouhal description was..” they were curly in 6 cases, wavy in 33 cases and straight in 10 cases. They were black in 16 samples, dark brown in 11, brown in 12, light brown in 1 and grey in 11 cases.” The colour alone would rule out the 80% negroid as an accurate description. Even asssuming all the black were negroid (being charitable), it still makes 24 brown v 16 black, showing a more Caucasian population, at about 60%, which is similar to modern populations in the area of Southern Egypt.

One criticism I have of this Brace paper is the assertion;

“We conclude that the Egyptians have been in place since back in the Pleistocene “

Which actually contradicts what he says about there being a population expansion from the Eastern Med that spread all of the Med Coast, in the same paper, and other evidence about the Capsian people of North Africa being part of the farming expansion form the Near East. It also contradicts DNA evidence about Eurasian back migrations into Africa dating to about 30,000 BP, and doesn’t provide any evidence to give a basis for this statement.

“the fact that so many European Neolithic groups in Figure 4 tie more closely to the Late Dynastic Egyptians near the Mediterranean coast than they do with modern Europeans provides suggestive support for an eastern Mediterranean source for the people of the European Neolithic at an even earlier time level than Bernal suggests for the Egyptian-Phoenician colonization and influence on Greece early in the second millennium BC.”

He has a habit of this kind of mistake in when he makes his summing up statements.

Racial differences in skull shape.

Firstly, the mostly obvious difference is that the Caucasoid top skull has a very flat profile, while the bottom skull is ‘prognathic’, meaning it’s jaws protrude out. Although not obvious from this image, the nose aperture of the Caucasian skull has a narrower triangle shape; with a longer, thinner bony protrusion at the point where the nose comes out from between the eyes (nuchal ridge). Caucasian skulls also posess a nasil sill (unless you see this shown, no explanation will make sense), Asian and African skulls don’t.

 

This site will give you all the detailed info if you are interested.

Racial differences in scalp hair.

The types of hair are pretty easy to tell apart, not due to width measurements, but due mostly to the cross section shape and pigment granule distribution.

Negroid hair…

is thin and almost flat in cross section (tape like), with a tendency to very tight curls. Sometimes it grows in tiny clumps, called peppercorn hair. African hair grows the slowest, at about 0.9cm a day. It’s angle of growth is very small, nearly parallel to the scalp. In colour, it is nearly always black in Africans. The only time you’ll see negroid hair of a different colour is if the individual is an albino, or has European ancestry, or if they dye it. Naturally coloured African hair has densely distributed pigment granules (hair shaft may be opaque) that are arranged in prominent clumps. The hairs also twist irregularly about their longitudinal axis, it has been described as a twisted oval rod.

Caucasian hair..

is a slightly irregular oval shape in cross section. It can to ruler straight, curly as an Africans, and every degree of curl between. It has the widest range of colours; black, auburn, shades of fair and brown to a near white blond. The hair grows out of the skull at an oblique angle, at a rate of about 1.2cm a month. the pigment granules are sparse to moderately dense with fairly even distribution .

Mongoloid hair..

grows the fastest at an average of 1.3cm a month. Its is more circular in cross section, although not perfectly regular. It grows out of the scalp at a right angle. The pigment granules are densely distributed and often arranged in large patchy areas or streaks. it is nearly always black.

Various links on racial variations of hair.

What is human hair. A light and scanning electron microscopy study

HAP Forensics Human Hairs Identification

Microscopy of Hair Part 1: A Practical Guide and Manual for Human Hairs

 

All three hair types under an electron microscope. The shape difference between  African and European hair doesn’t show well here though.

An interesting exception to the Asian hair average is Ainu hair, which I have seen described as Caucasian in cross section. it’s also reputed to come in dark brown and a reddish brown colour.

Lighter eyes means lighter skin?

While trying to locate information on whether hair colour lightens skin tone, I found a few articles suggesting that eye colour does, blue eyes particularly. Here’s a couple of studies I’ve found. From what I’ve read, it seems that several recessive genes (red hair, blue eyes) lighten skin colour. It’s not totally clear if it’s just through geographical association with other genes though.

Skin pigmentation, biogeographical ancestry and admixture mapping

Authors
Mark D. Shriver, Esteban J. Parra, Sonia Dios, Carolina Bonilla, Heather Norton, Celina Jovel, Carrie Pfaff, Cecily Jones, Aisha Massac, Neil Cameron, Archie Baron, Tabitha Jackson, George Argyropoulos, Li Jin, Clive J. Hoggart, Paul M. McKeigue, Rick A. Kittles

Ancestry informative markers (AIMs) are genetic loci showing alleles with large frequency differences between populations. AIMs can be used to estimate biogeographical ancestry at the level of the population, subgroup (e.g. cases and controls) and individual. Ancestry estimates at both the subgroup and individual level can be directly instructive regarding the genetics of the phenotypes that differ qualitatively or in frequency between populations. These estimates can provide a compelling foundation for the use of admixture mapping (AM) methods to identify the genes underlying these traits. We present details of a panel of 34 AIMs and demonstrate how such studies can proceed, by using skin pigmentation as a model phenotype. We have genotyped these markers in two population samples with primarily African ancestry, viz. African Americans from Washington D.C. and an African Caribbean sample from Britain, and in a sample of European Americans from Pennsylvania. In the two African population samples, we observed significant correlations between estimates of individual ancestry and skin pigmentation as measured by reflectometry (R2=0.21, P<0.0001 for the African-American sample and R2=0.16, P<0.0001 for the British African-Caribbean sample). These correlations confirm the validity of the ancestry estimates and also indicate the high level of population structure related to admixture, a level that characterizes these populations and that is detectable by using other tests to identify genetic structure. We have also applied two methods of admixture mapping to test for the effects of three candidate genes (TYR, OCA2, MC1R) on pigmentation. We show that TYR and OCA2 have measurable effects on skin pigmentation differences between the west African and west European parental populations. This work indicates that it is possible to estimate the individual ancestry of a person based on DNA analysis with a reasonable number of well-defined genetic markers. The implications and applications of ancestry estimates in biomedical research are discussed.

 
OCA2 controls eye colour, and TYR is a gene that harbours mutations for albinism. This seems to suggest that lighter eye colour could lead to lighter skin colour too. You see this in albino Africans, with partial albinism. They sometimes have blond hair and blue eyes, not the white hair and pink eyes of a full albino.

 I’m sure Razib said something about that on his blog…

  Fair skin Medium skin Olive skin
Blue/Blue 46.5 46.1 7.4
Blue/Brown 31.3 52.2 16.6
Brown/Brown 25.6 37.9 37.0

Please excuse the plagiarism. Full blog item here.

The paper he ‘s quoting from…

A Three–Single-Nucleotide Polymorphism Haplotype in Intron 1 of OCA2 Explains Most Human Eye-Color Variation

We have previously shown that a quantitative-trait locus linked to the OCA2region of 15q accounts for 74% of variation in human eye color. We conducted additional genotyping to clarify the role of the OCA2locus in the inheritance of eye color and other pigmentary traits associated with skin-cancer risk in white populations. Fifty-eight synonymous and nonsynonymous exonic single-nucleotide polymorphisms (SNPs) and tagging SNPs were typed in a collection of 3,839 adolescent twins, their siblings, and their parents. The highest association for blue/nonblue eye color was found with three OCA2SNPs: rs7495174 T/C, rs6497268 G/T, and rs11855019 T/C (P values of 1.02×10-61, 1.57×10-96, and 4.45×10-54, respectively) in intron 1. These three SNPs are in one major haplotype block, with TGT representing 78.4% of alleles. The TGT/TGT diplotype found in 62.2% of samples was the major genotype seen to modify eye color, with a frequency of 0.905 in blue or green compared with only 0.095 in brown eye color. This genotype was also at highest frequency in subjects with light brown hair and was more frequent in fair and medium skin types, consistent with the TGT haplotype acting as a recessive modifier of lighter pigmentary phenotypes. Homozygotes for rs11855019C/C were predominantly without freckles and had lower mole counts. The minor population impact of the nonsynonymous coding-region polymorphisms Arg305Trp and Arg419Gln associated with non-blue eyes and the tight linkage of the major TGT haplotype within the intron 1 of OCA2 with blue eye color and lighter hair and skin tones suggest that differences within the 5′ proximal regulatory control region of the OCA2 gene alter expression or messenger RNA–transcript levels and may be responsible for these associations.

And a more recent addition.

Interactions Between HERC2, OCA2 and MC1R May Influence Human Pigmentation Phenotype

Annals of Human Genetics doi:10.1111/j.1469-1809.2009.00504.x, Wojciech Branicki et al.

Human pigmentation is a polygenic trait which may be shaped by different kinds of gene–gene interactions. Recent studies have revealed that interactive effects between HERC2 and OCA2 may be responsible for blue eye colour determination in humans. Here we performed a population association study, examining important polymorphisms within the HERC2 and OCA2 genes. Furthermore, pooling these results with genotyping data for MC1R, ASIP and SLC45A2 obtained for the same population sample we also analysed potential genetic interactions affecting variation in eye, hair and skin colour. Our results confirmed the association of HERC2 rs12913832 with eye colour and showed that this SNP is also significantly associated with skin and hair colouration. It is also concluded that OCA2 rs1800407 is independently associated with eye colour. Finally, using various approaches we were able to show that there is an interaction between MC1R and HERC2 in determination of skin and hair colour in the studied population sample.

Anyone interested in this might be interested in Razibs more in depth look at this here

This is my all time number one post on this blog, about ten percent of hits have come from this. Lord only knows why but about 150 people a day look at it. Why this one?