A detailed critique of the European academy's handling of African genetic data, particularly the work of Cavalli Sforza. With the Human Geonome Project rolling along at full speed, Scott McEachearn wonders whether the European academy be trusted to render a balanced picture. Among his criticisms is that data on African peoples is being analyzed in ways different from that accorded European samples, for example with a lesser level of detail in some analyses that masks the picture on the ground. Another writer below claims that European "bio-prospectors" are busy mining African DNA data profitably, producing not only a distorted picture, but with little returned to the masses.
excerpt from: Scott MacEachern Genes, Tribes, and African History. Scott MacEachern. Current Anthropology Volume 41, Number 3, June 2000. p. 360-367
Some blurbs:
quote:
- African ethnic units are not bounded, homogeneous monoliths either frozen in place since before a.d. 1492 or caromming around the continent like culture-bearing billiard balls.
- A number of the groups used in the analyses in The History and Geography of Human Genes did not exist as such five centuries ago, and the modes of human interaction in Africa are not in any way reducible to a list of technological innovations and mass migrations. In part because of this lack of chronological control, the procedures used by Cavalli-Sforza et al. to associate genetic patterning with cultural events in the past are quite unsystematic, involving attempts to fit secondhand knowledge of archaeological, ethnographic, and linguistic reconstructions into a Procrustean bed of genetic patterning. Clark’s (1998) description of the “ransacking” of European genetic data for meaning applies equally well in the African case.
-Presumably, this patterning is explained by the admixture of “Caucasoid” and “Negroid” populations in northeastern Africa..
--These “Caucasoid” genetic contributions are thus invoked as the primary explanation for the variation exhibited in the first, second, and third principal components but seem to refer to different sets of genetic characteristics and thus presumably to different populations of “Caucasoids.” These interpretations would seem to lack much real explanatory value.
--The extent of this confusion of different data sources is made evident by a map (1994: fig. 3.9.3) that purports to show a pattern of Bantu expansion based upon archaeological data in which most of the linkages (between Nilotic-speaking peoples and Central-Western Bantu or between Bane populations and Northeastern Bantu, for example) are sustained by no archaeological data at all. No other mechanisms for genetic or linguistic dispersal are considered, and the con- nection of these different types of data seems quite unsystematic.
--Cavalli-Sforza et al. (1994:189–92) do not attempt to give historical explanations for African genetic frequency variation to the sixth principal component as they do for Europe.
-- The data given in this work indicate that such processes may be quite common on the African continent. In general, the correspondences between genetic relationships and those based upon linguistic and “tribal”/ethnic affiliation do not appear to be particularly close. Cavalli-Sforza et al.’s (1994:182–85) discussion of these correspondences abounds with perplexing relationships between different groups of people—Nubians with Moroccans, Ubangianspeakers with southwestern Bantu populations, Sara speakers of a Nilo-Saharan language with Hausa on the one hand and Biaka Pygmies on the other, and so on. The “Caucasoid” genetic affiliations of the San may prove to be another example.
--The Hausa, we should note, become Nilo–Saharans rather than speakers of Afroasiatic languages in the principal-component maps of Cavalli-Sforza et al.
-- Cavalli-Sforza et al. recognize the peculiarity of a situation in which one ethnonym encompasses two distinct genetic populations and respond by recalling Murdock’s (1959:414–15) distinction between pastoral Fulbe, who are supposed to be “Caucasoid-like,” and settled Fulbe, who are “Negroid.” They intimate that the Peul sample, which also contains genetic material from people identified as Tukolor, thus contains more admixture from “Caucasoid” (specifically Berber) populations. However, this well-known distinction between “cattle Fulani” and “town Fulani” is very frequently overdrawn..
-- the Wolof and Serer populations that cluster with the Peul are not particularly “Caucasoid,” and these westernmostWest African groups are certainly distinguished from Saharan populations according to Cavalli- Sforza et al.’s principal-component analysis (1994: 170).
--Indeed, historical data might lead us to expect such genetic results. This possibility seems to be comprehensively edited out of The History and Geography of Human Genes, presumably because European settlement in southern Africa took place after a.d. 1492. This claimed association of Khoisan people with “Caucasoids” is quoted in more recent works on genetics and history in Africa, among them the work by Passarino et al. (1998) on Ethiopian populations. This latter paper exhibits the same reliance upon inappropriate sources as does Cavalli-Sforza et al., with for example use of a 1964 Encyclopedia Britannica article as a primary reference on the prehistory of Ethiopia.
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MacEachern Genes, Tribes, and African History F 365. continued --------------------------------
quote:
"It is thus extraordinarily ironic that Cavalli-Sforza, Menozzi, and Piazza in their attempts to elucidate the ancient genetic history of the whole of humanity find it necessary to posit that Africans, as well as members of indigenous groups in other parts of the world, really have been people “without history” (Trevor-Roper 1965:9) since a.d. 1492. If anything, the continent of Africa, at least, has for the past 500 years suffered from a surfeit of history, not its lack. The relatively recent and closely connected developments of nationalism and colonialism have certainly generated a hierarchy of states, ethnies, and “tribes” that can command the loyalties of people living in different parts of the world today, but the extension of those units into the past is a proposition to be tested, not a given.
The recent creation of “tribal” identities is not the only process of ethnic-group definition in Africa that fails to accord with the assumptions made in The History and Geography of Human Genes. The mosaic of peoples described by Roderick McIntosh (1998; see also McIntosh 1993) in The Peoples of the Middle Niger: The Island of Gold appears to be of very long standing indeed, with roots ultimately to be located in the mid-Holocene, but the complex and evolving relations between different specialist communities convincingly depicted in that work bear very little resemblance to ahistorical, static models of African “tribes.” This mosaic of groups incorporated people of different language affiliations; it involved extremely sophisticated ritual, economic, and technological accommodations to a diverse and changing natural and cultural milieu; it allowed for processes of immigration, emigration, and population interchange. Such constellations of interacting groups can be found elsewhere in Africa as well, although probably none have been as intensively investigated and described as the Middle Niger populations. Interaction between peoples, in Africa and elsewhere, is a continuing and complex process and only rarely involves the spasms of mass migration that Cavalli-Sforza et al. invoke.
Modern concepts of ethnicity and the social groupings that result from those concepts seem if anything more closely comparable to the demes studied by population geneticists than to the “tribes” created by colonialists and ethnographers and adopted as units of study by Cavalli- Sforza et al. Demes are not necessarily held to have sharp boundaries, and intergrades between demes at particular levels are both clinal and common. Similarly, the exact characteristics of particular demes may be defined in reference to particular research problems. This somewhat resembles instrumentalist formulations that locate ethnic identities in situationally contingent bundles of social and cultural identifications that can assume differential importance in different social situations while simultaneously existing at multiple social and spatial levels (Barth 1969, Cohen 1978, Handelman 1977, Mc- Kay 1982). Ethnoarchaeological research by a number of investigators working in Africa (David 1992, Hodder 1982, Larrick 1986, MacEachern 1998, Wiessner 1984) has detected similar patterning in material culture. It is unlikely that such patterning would derive from the ahistorical monoliths identified as “tribes” by Cavalli- Sforza et al. (1994).
---------------------- MacEachern Genes, Tribes, and African History F 365. continued -------------------------------- quote: African Examples
As in each other continental area investigated, Cavalli- Sforza, Menozzi, and Piazza treat their data on African genetic variation in different ways and for somewhat different purposes. Trees of genetic distance and similarity are generated through average linkage analysis in order to elucidate phylogenetic relationships between modern populations and the histories of ancient fissioning that have resulted in those modern populations. Two-dimensional principal-component analyses of variation in genetic characteristics allow an alternative, graphic presentation of modern population affinities for comparison with the phylogenetic trees. Studies of the distributions of single alleles of particular genes yield data on (and allow speculation about) particular environmental adaptations and interactions between different human groups; these data are somewhat beyond the bounds of this paper. Finally, synthetic maps of each region are derived from the results of principal-component analysis of multiple gene frequencies—for 79 genes in the African case, for example. As in the European instance noted above, Cavalli-Sforza et al. usually assert that the spatial patterning of values for each principal component is a reflection of a specific population/language movement (again, the two are often not differentiated) in the past. I will first examine some features of the African genetic tree and principal-component map given in Cavalli- Sforza et al. (1994:169, 170) and then examine the synthetic maps of the continent. I emphasize that this inquiry is very far from being comprehensive, but I hope that it will be illustrative.
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Fig. 1. Genetic tree of 49 African populations (Cavalli- Sforza, Menozzi, and Piazza 1994:fig. 3.5.1; q1994, Princeton University Press, reprinted by permission of Princeton University Press). trees and principal-component analysis North African groups. The continental genetic tree of African populations generated by Cavalli-Sforza, Menozzi, and Piazza (reproduced here as fig. 1) uses genetic data from 49 human groupings in Africa. The most fundamental differentiation shown is that between sub-Saharan Africans, on the one hand, and Saharan and Northern African populations, on the other. It is among the latter group (16 of the 49) that we see the only national identifications of populations (Algerians, Sudanese, Moroccans, Tunisians, Libyans, Egyptians), whereas, as noted above, such identifications are the rule across the Mediterranean in Europe. The other Saharan/ Northern African and all the sub-Saharan population samples identified are denoted by (1) “traditional” ethnonyms (Amhara, Hausa, Sandawe, and so on), (2) geographical designations (Bantu, N.E., Bantu, S.W., and so on), (3) designations based on language affiliation (Nilotic, Ubangian, Volta, San), or (4) designations based on particular physical characteristics (Pygmy/“Pygmoid”). As noted above, appendix 3 makes the human diversity of many of these samples obvious.
Within the Saharan/Northern African group there are two subclusters. One is comprised of a number of “national” North African populations (Moroccan, Tunisian, Libyan, Egyptian), as well as Nubian, Bedouin, Berber, and Canarian. Cavalli-Sforza et al. (1994:172) note that there are few data available on the genetic makeup of the Canarian group, and it is not clear whether they are data on modern peoples or on the extinct Guanches. The other cluster consists of a number of Northeast African populations, including the national Sudanese and a generalized Cushitic-speaking group. Within this Northeast African group, one subcluster does not conform to historical or linguistic expectations, as it associates the Algerian national population fairly closely with the Beja of eastern Sudan and somewhat more distantly with the Berber-speaking Tuareg; the latter group thus appears to be rather distinct from other Berber populations. Cavalli- Sforza et al. (pp. 172–73) posit an ancient relationship between Tuareg and Beja, largely, it appears, on the basis of their shared status as pastoralists. There are no other data that I know of that indicate such a link, and in any case it does not explain the putative close relationship of modern Algerians to both groups. The researchers note that they have data on relatively few genes from this Algerian group, but it should be pointed out that such small data sets are no obstacle to the acceptance of particular genetic associations when these fit their expectations— the Canarian case noted above is a good example.
This pattern of acceptance and rejection of generally equivalent data on the basis of their concordance with expectations is common throughout The History and Geography of Human Genes and is an example of the strategy of post-hoc accommodative argument noted by Clark (1998).
The distinction between Saharan/Northern African populations and peoples living in sub-Saharan Africa is explained by the varying contribution of genes from “Caucasoid” populations in Europe and Southwest Asia to the former. This is very likely a contributing factor, given the archaeological and historical evidence of such population interactions around the Mediterranean. It is also quite likely that clines in gene frequencies across the Sahara are in part the result of natural selection operating upon characteristics that are not adaptively neutral in the very different environments through this region. There is a significant amount of evidence for both climatic and latitudinal effects upon different gene frequencies (Cavalli-Sforza et al. 1994:143; Mastana, Constans, and Papiha 1996; O’Rourke, Suarez, and Crouse 1985; Spitsyn et al. 1998). The greater instability of Saharan environments through time probably offered less scope for such in situ adaptation than is the case among, for example, the Nile Valley populations examined by Brace et al. (1996).
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Saharan and Sahelian groups (various Berber- and Arabic- speaking populations, including Tuareg and groups subordinated to them, such as the Bella and the Haratine and Saharan-speakers such as the Chaamba, Reguibat, Teda, and Kanembu) are not covered in detail in the work (Cavalli-Sforza et al. 1994:173), although investigations of biological variation among those populations have indicated that their anthropometric and genetic affiliations are very diverse and complex (Froment 1999). This lack of data on intermediate groups may make human physical and genetic distinctions across the Sahara appear more clear-cut than they are. The status of these populations is particularly important given that climatic change rendered significant parts of the Sahara passable (and in some cases habitable) through periods in the Holocene at least, with the result that there is abundant evidence of more extensive human contacts across the desert than have existed in historic times. Sutton (1974) and Ehret (1993) have suggested that the Saharo-Sudanese Neolithic tradition was largely the province of Nilo- Saharan-speakers. Populations speaking those languages do not, however, occupy an intermediate position between North African and sub-Saharan African populations, suggesting that either the correlations between archaeology and linguistics or those between genetics and linguistics—or both—are erroneous.
While Cavalli-Sforza et al. emphasize the contribution of immigrant genes to the modern genetic makeup of Saharan/Northern African populations, they do not really consider the possibility of an African genetic contribution to either Europe or the Near East. It thus appears that Africa accepts genetic contributions from other areas but does not reciprocate them. A principalcomponent map of 42 world populations (Cavalli-Sforza et al. 1994:82) indicates a somewhat more complex picture, with a succession of Basques, Sardinians, Near Eastern populations, and Berbers occupying a space intermediate between African and European populations, although certainly arrayed closer to European groups. This assumption is also at variance with the known history of the region, where we see evidence for two-way relations throughout the Holocene, especially via Southwest Asia and the Iberian and Italian peninsulas. People from North, Saharan, and sub-Saharan Africa have crossed the Mediterranean as settlers, conquerors, and slaves through recorded history just as have Europeans. In recent times such population flows may have tended to be from north to south, but it should not be assumed that this has always been the case.
Pygmies, Khoisan, and Caucasian connections. The high-level cluster of sub-Saharan African populations contains 33 of the 49 populations of the phylogenetic tree. It is a considerably more diverse grouping than the Saharan/Northern African, with multiple subclusters at different fissioning points. The most famous “outlier” populations of traditional African ethnography are of course Pygmy and Khoisan-speaking groups, which are to varying degrees physically distinct from their African neighbors and also to varying degrees participate in foraging economies. These latter are frequently seen by Westerners as archaic, and Pygmy and Khoisan populations have often been identified as unchanged relics of earlier ages (e.g., Thomas 1959:6–8;Turnbull 1983:11–13, 157–58). Pygmy (Mbuti and Biaka) and “Pygmoid” populations are found at various points on Cavalli-Sforza et al.’s phylogenetic tree as outliers and with other groups. As Froment (1998) points out, this separation of Pygmy and other African populations is extremely imprecise; it depends to a great extent upon linguistic criteria, ignores the numerous transitional populations (not only those denominated as “Pygmoid”), and systematically discounts the fact that we know very little about the historical and physical relations between these groups over any significant period of time.
---------------------- MacEachern Genes, Tribes, and African History .. . continued -------------------------------- Similarly, Khoi and San populations cluster with a Somali sample (which itself is held to be out of place, given that Somali groups geographically sit within the Northern African range), while Sandawe clusters with populations from Senegambia and Hadza is an outlier between the two. Cavalli-Sforza et al. (1994:169–70, 174–77, 189–93) posit that especially San populations are the result of admixture between “Caucasoid” groups originating in Southwest Asia and African “Negroid” groups. This is supposed to be a different process of interaction across the Red Sea from the one that yielded the distinctive genetic and physical characteristics of Ethiopian populations; indeed, the San and Ethiopian peoples are held to be “similar to Caucasoids but . . . otherwise very different [from one another]” ( p. 191). The historical mechanisms—and even the demographic meaning—of such multiple similarities are left unspecified. This is unfortunate, given that hypotheses of immigration into Africa by (often “Hamitic”) “Caucasoids” have bedeviled African history and archaeology for much of the past century, often being advanced to explain away African cultural innovations and based on very unsatisfactory evidence. One would have hoped that consciousness of this situation would have led the authors of The History and Geography of Human Genes to substantiate this hypothesis in detail.
The nongenetic evidence marshaled in support of the hypothesis of relations between San groups and populations in the Near East is extremely weak. A putative “Asian” genetic contribution to forager groups in Ethiopia (Nijenhuis and Hendrikse 1986) is discussed only with reference to “Pygmoid” populations, although Cavalli- Sforza et al. (1994:174) imply that these groups are related to the San. They claim ( pp. 160, 176) that skeletal material “credibly identified as San” has been found in various parts of North and East Africa, including northern Egypt, but note only parenthetically that this assertion in Nurse, Weiner, and Jenkins (1984) is based upon a 30-year-old paper by Philip Tobias (1968 [1964]). The Tobias paper does not in fact seem to make that claim, and it is in any case disputed by more recent researchers on the basis of the characteristics of the material involved, the very fragmentary state of the collections, and known problems with the accumulation of Khoi and San skeletal reference collections (Froment 1998; Morris 1986, 1987; Rightmire 1975; 1984:193–98; Schepartz 366 F current anthropology Volume 41, Number 3, June 2000 Fig. 2. Principal-component analysis of 49 African populations. BNT, Bantu and Bane; C, Central; ETH, Ethiopia; KH, Khoisan; N, North Africa; NS, Nilo-Saharan; PG, Pygmies; W, West Africa (Cavalli-Sforza, Menozzi, and Piazza 1994:fig. 3.5.2; q1994, Princeton University Press, reprinted by permission of Princeton University Press).
1988). In fact, the identification of this skeletal material from northeastern Africa as related to San skeletal material from southern Africa is very doubtful; the material indicates that ancient populations in the area were most closely affiliated with the present-day inhabitants. The only widely accepted evidence of ancient Khoisan populations in East Africa is the ascription of the Sandawe and Hadza languages to the Khoisan phylum (with even less well-attested traces of Khoisan contacts in Dahalo and Yaaku [Ehret 1974:11, 88]). However, the Khoisan affiliations of Sandawe and/or Hadza are still disputed by some linguists, and in any case the available genetic data do not indicate a close relationship between Sandawe and Hadza people, on the one hand, and San and Somali people, on the other. The paradox is obvious: Sandawe and Hadza provide the only firm link between San populations and northeastern Africa (a linguistic one), but according to the genetic data that provide the basis for The History and Geography of Human Genes they are more closely related toWest and Central African groups (fig. 2). There seems to be no a priori reason to associate Khoisan-speaking populations with Southwest Asia on the basis of San genetic data and not to associate Khoisan-speaking populations with Senegambia on the basis of Sandawe genetic data, but this is just what Cavalli- Sforza et al. do. It is also, of course, possible that either or both associations are spurious, especially given the small size of some of these forager groups and the attendant possibility of genetic drift.
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We must remember, as well, that the southern tip of Africa is not in fact occupied only by Khoisan and other African peoples, as the discussion in Cavalli-Sforza et al. (1994:158–68) would sometimes seem to imply. It is also the only part of the continent to have seen extensive settlement by Europeans (and Asian people arriving in the context of colonization) over the past four centuries. This has certainly involved a considerable amount of genetic interchange between indigenous and immigrant populations, along with the formation of a number of communities of mixed descent, with genetic, cultural, and linguistic affiliations to Khoisan, other African, European, and Asian groups. These communities and their origins are discussed at some length in Nurse, Weiner, and Jenkins (1985:221–40); they have at various times and in various areas included !Kora, Baster, Orlam, Gyzikoa, Griqua, and “Cape Coloured” populations, among others, and have occupied territories in South Africa, Namibia, and Botswana. As Morris (1992, 1997) points out, “Caucasoid” genetic and morphological features seem to be less important among Griqua populations (the only cases that I know of for which these affinities for these groups have been studied) than might have been expected on historical grounds, but these groups are quite diverse, and rather little is known of genetic exchange between European and African populations on the frontiers of European settlement in southern Africa.
It would seem reasonable to seek evidence for “Caucasoid” genetic affiliations among southern African populations in this recent and relatively well-attested contact situation rather than in putative Khoisan contacts with Northeast Africa and Southwest Asia for which no firm evidence exists. Indeed, historical data might lead us to expect such genetic results. This possibility seems to be comprehensively edited out of The History and Geography of Human Genes, presumably because European settlement in southern Africa took place after a.d. 1492. This claimed association of Khoisan people with “Caucasoids” is quoted in more recent works on genetics and history in Africa, among them the work by Passarino et al. (1998) on Ethiopian populations. This latter paper exhibits the same reliance upon inappropriate sources as does Cavalli-Sforza et al., with for example use of a 1964 Encyclopedia Britannica article as a primary reference on the prehistory of Ethiopia.
West African cases. As noted above, the Sandawe sample clusters with samples from westernmostWest Africa, specifically from Serer, Wolof, and Peul populations. It was this latter group that first caught my attention when I looked at Cavalli-Sforza et al.’s phylogenetic tree because of the distinction between the Peul and Fulani samples that I have mentioned. These two ethnonyms both denote Fulbe people, but the Fulani sample is closely associated with a set of samples from Nigerian populations, including Ibo, Yoruba, and Hausa—groups a long way from Senegambia. Cavalli-Sforza et al. recognize the peculiarity of a situation in which one ethnonym encompasses two distinct genetic populations and respond by recalling Murdock’s (1959:414–15) distinction between pastoral Fulbe, who are supposed to be “Caucasoid-like,” and settled Fulbe, who are “Negroid.” They intimate that the Peul sample, which also contains genetic material from people identified as Tukolor, thus contains more admixture from “Caucasoid” (specifically Berber) populations. However, this well-known distinction between “cattle Fulani” and “town Fulani” is very frequently overdrawn (for other considerations of the issue, see e.g., Curtin 1975:19–22; Irwin 1981:46–55; Schultz 1981), the Wolof and Serer populations that cluster with the Peul are not particularly “Caucasoid,” and these westernmos tWest African groups are certainly distinguished from Saharan populations according to Cavalli- Sforza et al.’s principal-component analysis (1994: 170).
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It is more likely that this distinction between the populations recorded as Fulani and Peul can in great part be traced to social/political processes over the past 200 years in West/Central Africa, where among other events the jihad of Uthman dan Fodio led to the establishment of the Sokoto Caliphate in modern Nigeria and Cameroon and to an attendant favorable change in the status of a Fulbe ethnic identity. Under these circumstances, we would expect that many indigenous people, especially those of Hausa background but also including members of other Nigerian and Cameroonian societies, would attempt to assimilate to that Fulbe identity. Indeed, such processes are often discussed and debated in the Nigerian historical literature (Salamone 1985, Smith 1997) and can probably be seen in play in the mixed ethnic affinities of the “Fulani” sample in appendix 3 of The History and Geography of Human Genes (Cavalli- Sforza et al. 1994:470).3 Difference between “Peul” and “Fulani” thus appears to be not the result of a longstanding division of two populations subsumed under one ethnonym but quite the opposite—the relatively recent creative manipulation of identity for political and social advantage.
The significance of this conclusion lies not so much in the ethnographic concepts used by Cavalli-Sforza et al. as in the possibility of such a drastic change in lin- 3. The Hausa, we should note, become Nilo–Saharans rather than speakers of Afroasiatic languages in the principal-component maps of Cavalli-Sforza et al. (1994:170, 181; see fig. 2) and “elongated” pastoral nomads a` la Hiernaux in the conclusions to the chapter on Africa (p. 194). These incorrect ascriptions indicate the difficulty, especially for nonspecialists, of working with such very large ethnographic and linguistic data sets. This difficulty probably also accounts for citations of, for example, works dealing with Chukotskii and Brazilian populations in references to African groups (p. 471).
linguistic and ethnic affiliation by a significant group of people in less than two centuries. If such a change happened in northern Nigeria, how common is it elsewhere, and how many such changes affect the analyses in The History and Geography of Human Genes? The data given in this work indicate that such processes may be quite common on the African continent. In general, the correspondences between genetic relationships and those based upon linguistic and “tribal”/ethnic affiliation do not appear to be particularly close. Cavalli-Sforza et al.’s (1994:182–85) discussion of these correspondences abounds with perplexing relationships between different groups of people—Nubians with Moroccans, Ubangianspeakers with southwestern Bantu populations, Sara speakers of a Nilo-Saharan language with Hausa on the one hand and Biaka Pygmies on the other, and so on. The “Caucasoid” genetic affiliations of the San may prove to be another example.
Technological innovations, population expansions, and especially migrations are invoked to explain as many of those relationships as is possible, but these explanations often seem ad hoc. For example, archaeological and linguistic data involving the Bantu expansion are invoked to explain the apparently very close genetic relations between northwestern and southeastern Bantu populations. Surely, however, any such explanation should also account for the relative lack of genetic similarity of the intervening Bantu populations (table 1). In any case, the close relations between archaeological and linguistic reconstructions (the former very dependent upon the latter) in this case vitiate their separate use as independent tests. Indeed, Vansina (1995) has cogently critiqued the assumptions that there are close parallels in archaeological and linguistic data bearing upon the expansion of Bantu languages and that that expansion was the result of a single, massive migration process. The archaeological and linguistic data simply do not yield the neat, uncomplicated picture of the past that Cavalli-Sforza et al. present. The extent of this confusion of different data sources is made evident by a map (1994: fig. 3.9.3) that purports to show a pattern of Bantu expansion based upon archaeological data in which most of the linkages (between Nilotic-speaking peoples and Central-Western Bantu or between Bane populations and Northeastern Bantu, for example) are sustained by no archaeological data at all. No other mechanisms for genetic or linguistic dispersal are considered, and the con- nection of these different types of data seems quite unsystematic.
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Synthetic maps of african genetic variation
Cavalli-Sforza et al. (1994:189–92) do not attempt to give historical explanations for African genetic frequency variation to the sixth principal component as they do for Europe. (Perhaps they would have done so if there were as many different regional historical reconstructions for Africa as there are for Europe.) Instead, they limit their explanations to the first four principal components, which encompass about the same percentage of total variance as in the European case. The synthetic map derived from the first principal component (fig. 3) has a strong north-south gradient, with opposing extremes along the Mediterranean coast and from the Equator southward. The researchers relate this to the ancient presence of “Caucasoid” populations along the northern coast of Africa and the gradual admixture of “Caucasoid” and “Negroid” populations across the Sahara. They also comment upon the paucity of data on Saharan populations. As noted above, we should remember that this gradient is also an environmental one and that it is quite likely that environmental variability is affecting the genetic makeup of African populations to some degree.
The discussion of patterning on the synthetic maps for the second and third principal components is rather confusing. Cavalli-Sforza et al. (1994:189) note that both maps show maximum values in northeastern Africa, although the specific association with Ethiopia is not as clear as they claim. They state that the map of the second principal component indicates a similar set of maximum values in the area of southwestern Africa occupied by Khoisan-speakers in precolonial times and that this indicates that there existed a population ancestral to modern Khoisan peoples somewhere near Ethiopia. Low values on the second principal component in the areas intervening between Ethiopia and the Kalahari are ascribed to the later settlement of those areas by Bantu peoples. The maps (figs. 4 and 5) actually indicate that this pattern is based upon variation in the third principal component. The difference is significant, given that the second principal component explains 18.6% of the total variance and the third only 10.3%, but the text seems to indicate that this pattern is in fact associated with the second.
Presumably, this patterning is explained by the admixture of “Caucasoid” and “Negroid” populations in northeastern Africa that Cavalli-Sforza et al. believe gave rise to the Khoisan peoples. However, the maps for the second and third principal components show almost opposing values along the Mediterranean coast, where the presence of “Caucasoid” groups is held to be the explanation for the patterning of the first. Similarly, northeastern and southwestern Africa show maximum divergence on the third principal component, which is accounted for by their differences from one another in a context of general relationship to “Caucasoid” groups. These “Caucasoid” genetic contributions are thus invoked as the primary explanation for the variation exhibited in the first, second, and third principal components but seem to refer to different sets of genetic characteristics and thus presumably to different populations of “Caucasoids.” These interpretations would seem to lack much real explanatory value.
The fourth principal component accounts for only 7.0% of the total variance (fig. 6). Maximum values are associated with the northwestern part of the Central African tropical forest and minimum values with the border regions of Mali, Niger, and Burkina Faso. Parsimoniously, the researchers associate these maximum and minimum values with two different agricultural expansions. They associate the area of maximum values with an expansion of Bantu populations, although one might associate the patterning with Adamawa-Ubangian groups as well (David 1982:88–91; Saxon 1982) and the influence of this massive Bantu migration upon genetic variation would seem to be extraordinarily low compared with that of the “Caucasoid” gene flows that have determined the nature of the first three principal components. They admit that there is no equivalent evidence for an agricultural expansion from the area of minimum values in the West African Sudanic zone but counsel future comparison with archaeological data. These syn- thetic maps sometimes appear to function as historical Rorschach tests, with genetic data being associated with ancient cultural processes on the basis of general resemblances in spatial patterning.
Conclusions
The History and Geography of Human Genes is an extraordinary compendium of information on human genetic variation. It links a huge amount of data on that variation with archaeologically, historically, and linguistically known cultural processes that took place at various times and in various areas. Its hypotheses have been provocative and in many cases useful, and researchers in other fields have responded to them in ways that will eventually increase our knowledge of our shared human past. In the long run, Cavalli-Sforza et al. have probably established the examination of patterns in genetic characteristics as a valuable complement to older, more established avenues for the examination of prehistory. This genetic research was limited by the lack of samples from many areas, by the necessity of using samples collected under very different conditions, by the great variation in the amount of information available on the composition of the groups being sampled, and by the lack of availability of statistical techniques that could account for interactions between groups during the process of constructing phylogenetic trees. To their credit, Cavalli-Sforza, Menozzi, and Piazza recognize and highlight a number of these problems and try to compensate for them. Their solutions are often sophisticated and ingenious, and the potential of these techniques is obvious.
The danger for African archaeology is that the very impressive amount of genetic data amassed in The History and Geography of Human Genes will convince nonspecialists of the validity of the hypothesized associations between human groups. That would be unfortunate, because this pioneering synthesis is hobbled by a conceptual model of human behavior that takes little account of ethnographic, historical, linguistic, and archaeological research on the constitution of human societies and of the various ways in which cultural meaning is constructed in the continuing negotiation of individual and group identities. Similarly, the discussion of relations between language and ethnicity pays virtually no attention to linguistic analyses of such relationships. Their compilation of the data that make up the African sample should have indicated to the researchers that these relations are extremely complex, while the varying criteria—linguistic, geographic, national—used for identifying populations make it seem unlikely that the groups under study are comparable entities.
African ethnic units are not bounded, homogeneous monoliths either frozen in place since before a.d. 1492 or caromming around the continent like culture-bearing billiard balls. They are dynamic entities, manipulated in response to changes in the natural and social environment, and their composition can change very quickly indeed. Differences in the temporal resolutions of genetic, linguistic, archaeological, and historical analyses are one of the main difficulties in these multidisciplinary studies, and the ability to control chronologies is more restricted in the former two disciplines than in the latter. It is often difficult, therefore, to establish whether the genetic patterning exhibited by modern populations can be traced back to events that happened centuries or millennia ago. A number of the groups used in the analyses in The History and Geography of Human Genes did not exist as such five centuries ago, and the modes of human interaction in Africa are not in any way reducible to a list of technological innovations and mass migrations. In part because of this lack of chronological control, the procedures used by Cavalli-Sforza et al. to associate genetic patterning with cultural events in the past are quite unsystematic, involving attempts to fit secondhand knowledge of archaeological, ethnographic, and linguistic reconstructions into a Procrustean bed of genetic patterning. Clark’s (1998) description of the “ransacking” of European genetic data for meaning applies equally well in the African case.
The deme concept, often used in population genetic research in other species, would seem to be a better and more flexible fit for the study of human genetic variation mac eachern Genes, Tribes, and African History F 371 than “tribal” typologies borrowed wholesale from ethnographic research done 50 or more years ago, especially since it seems to find resonances in some more recent concepts of ethnicity. It remains to be seen whether it will be applied to human genetic research in Africa and elsewhere. It would be interesting to see, for example, whether human demes on some level correspond to the material distributions that we call archaeological traditions, without any attempt to fit either genetics or archaeology to the straitjacket of the ethnographic “tribe.” Archaeological distributions of artifacts frequently occur over much larger territories than do the ethnic (“tribal”) units that ethnographers study in the present, and it is possible that in some cases this reflects movements by artifact producers, especially women, that would also be reflected in patterns of genetic variation (MacEachern 1998). In general, research on the African past would at this point benefit far more from small-scale studies of genetic patterning within and between particular communities than from the continental and subcontinental approaches that make up The History and Geography of Human Genes.
The genetic data available for Africa have serious limitations, but the patterns of variation demonstrated by these data are interesting and probably do indicate patterns of cultural interaction in the past. There are, however, good reasons to be suspicious of efforts to correlate those patterns with cultural processes at the level of specificity attempted by Cavalli-Sforza et al. The project of correlating the data from these different kinds of investigation still lies well before us, and it would be a great mistake to assume that such correlations will be self-evident. Research that has as its goal the study of the history and geography of human genes in Africa and elsewhere must be truly interdisciplinary, working with the best knowledge of other disciplines that can be acquired. A study that uses the terminology of other disciplines but takes insufficient account of the concepts behind that terminology risks generating misleading reconstructions of human history and prehistory. ============
KEITA WEIGHED IN:
s . o. y. keita 1925 2nd St., N.W., Washington, D.C. 20001-1667, U.S.A. 30 xi 99 mac eachern Genes, Tribes, and African History F 375 --------------------------------------------------
MacEachern has given us an effective critique of the African chapter in Cavalli-Sforza et al.’s book, while also illustrating general theoretical problems in syntheses of archaeology, ethnicity, linguistics, and human biology. The insights offered are especially useful for those interested in Africa, for which scholarship has long been hampered by myths and stereotypes. Notable among these is a paradigm which sets limits on authentic biocultural indigenous Africanness; this surprisingly persists in some scientific literature. The work of even some Africanists is still influenced by this legacy, which usually manifests itself around the problematic construct of race. Although MacEachern has given a cogent presentation, there are a few concerns.
One wishes that emphasis had been placed on the African origin and differentiation of the Afro-Asiatic language family and its subsequent spread to Asia (Greenberg 1966; Bender 1975; Diakonoff 1965, 1981; Ehret 1984, 1995; Ruhlen 1991). The dubious Nostratic construct has been used to postulate the spread of food production into Africa (from Asia) by Afro-Asiatic-speakers. Significantly, reconstructed common Afro-Asiatic has no terms for food production (Ehret 1984, 1995) and is accorded the same time depth as Nostratic (cf. Ehret 1984 and Barbujani and Pilastro 1993). Furthermore, most Nostraticists now conceptualize Afro-Asiatic to be a sister to Nostratic, not a daughter (Ruhlen 1991). Finally, archaeological data support migration from Africa into the Near East during the time frame suggested by some Nostratic models for immigration into Africa (cf. Bar- Yosef 1987 and Barbujani and Pilastro 1993).
On a technical note, MacEachern has made a common error, that of easily equating phenetic similarity with a necessary genealogical relationship. The results of mathematical techniques employed by human biologists must be interpreted with sound biological principles and other information (Rhoads 1984, Harrison 1984). The fact that small samples of Beja and Algerians and then of Nubians and Moroccans cluster clearly cannot be taken as necessarily indicative of a close genealogical relationship. The similarity may have many explanations including chance, especially since, as MacEachern notes, the nature of any links between earlier and later peoples having these designations remains an open question.
This is even more so when selection, migration, gene flow, and language shift have to be integrated into explanatory models. Harrison (1984:61), considering the results of simulations which evaluate interpopulation gene flow with and without selection, points to another important issue concerning migration and population affinities: the causes of inter-population patterns of gene frequency variation, and the meaning of affinities based not on ancestry but on genetic similarity. Clearly with varying levels of selection, populations which are genetically similar may have a much more remote common ancestry than populations which are genetically more different.
The lack of criticism on this point does not, however, seriously weaken the overall critique.
In fact, there is little to quibble with in MacEachern’s effort. However, he is perhaps somewhat overconfident in the belief that genetic research has led to the “dismemberment” of racial taxonomies and racio-typological thinking. While few write today in terms of Nordic or Jewish races, and this is a result of research and the World War II experience, there is still plenty of work on Africa which constructs its interpretations of diversity explicitly or implicitly in terms of conceptually idealized “Caucasoid” and “Negroid” “taxa,” implying a causal or foundational linkage between morphological complexes and a variety of genes.
Cavalli-Sforza et al.’s book is one example of this kind of work at some level. For some reason MacEachern does not directly engage its underlying nonevolutionary raciotypological model of interpretation or its use of racial terms, which are ontologically misleading in that they imply that supra-Saharan Africans were originally European- derived. These people supposedly interacted with “Negroids” and others, receiving some genes but contributing a lot more and thus becoming the primary explanation of African diversity. MacEachern’s critique would be even more useful if he had pointed out that
(1)fossils indicate the presence of anatomically modern people in supra-Saharan and Nile Valley Africa at a time when hominids in Europe had Neanderthal morphology;
(2) coalescence (and therefore differentiation) times for numerous genes sampled globally from living humans date to a period when modern morphology had not yet emerged or was to be found only in Africa; and
(3) global genetic diversity seems largely to be a subset of that found in Africa. (Whether this dates back to the time of Homo erectus or modern H. sapiens matters little; the diversity denoting the mythical “racial divergence” exists in Africa, as should be expected, and antedates the existence of the morphologies used to define races.) MacEachern fails to make these points, which together indicate that the African genetic profiles and morphologies being interpreted as solely resulting from European (or Southwest Asian) colonization and/or admixture (with “Negroids”) are largely the product of various authentic intra-African biohistorical processes which perhaps date to a time before there were any anatomically modern Europeans.
However, the Holocene climatic fluctuations of the Sahara (Hassan 1988), probable Late Pleistocene (and Holocene) population increase in response to changing subsistence regimes (Wetterstrom 1993), and the spread of early Afro-Asiatic-speakers from the Horn surely also had some effects. Supra-Saharan Africa is not primarily a product of extra-African colonization. There are many ways to be biologically African— many morphological combinations and genes (Hiernaux 1974, Keita and Kittles 1997).
The frequency of neutral private alleles of the right date and demonstrably originating outside of continental Africa will have to be determined before the non-African contribution to Africa’s genetic picture can be fully assessed. MacEachern seems to accept the racio-typological model of explanation at the larger level. Nevertheless, he contributes to the paradigm shift in understanding African biological variation, which will reject racio-typological thinking and use the reality of indigenous African diversity as an analytic tool.
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alan g. morris Department of Anatomy and Cell Biology, University of Cape Town Medical School, Observatory 7925, South Africa (morris@anat.uct.ac.za). 17 xi 99
"MacEachern’s other major complaint about the compendium by Cavalli-Sforza et al. is the use of principal components to generate synthetic maps which are then interpreted as signs of specific past events. The principal components are not events. They are mathematical relationships and as such as far too complex to be given simple historical interpretations. MacEachern, in line with Clark’s (1998) assessment, accuses Cavalli-Sforza et al. of having a “pattern of acceptance or rejection of generally equivalent data on the basis of concordance with expectations.” Simplified, this means that they saw what they wanted to see. I entirely agree with Mac- Eachern’s concern that many students of anthropology, genetics, and history are going to take Cavalli-Sforza et al.’s work at face value. By doing that, they may be uncritically reproducing interpretations of the nature of ethnic identity into account.
This is not the first time that I have looked at the difficulties in interpreting genetic data. The equivalent genetic history of southern African people was published by Nurse, Weiner, and Jenkins in 1985. Again, the work was a wonderful production of data on a wide range of peoples, but the authors’ attempts at linking what they saw in the genes with history were sometimes very wide of the mark. Social theory and social events are not easily explained by biology. As does MacEachern here, I ended my comments by warning of my great fear “that students of archaeology, genetics and physical anthropology will simply assume that this is the academic ‘bible’ on the subject and will absorb many of the speculative passages without criticism” (Morris 1988:5).
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mark pluciennik Department of Archaeology, University of Wales, Lampeter, Ceredigion SA48 7ED, Wales, U.K. (m.pluciennik@lamp.ac.uk). 11 x 99
"MacEachern notes that the various “academic and political” uses for human genetic research raise the most troubling questions when driven by a regime of private property. I share his concern that Western bio-prospectors promote an “identification of indigenous peoples with their surroundings” in part to performa metonymy whereby people become resources. If thus identifying indigenous people reduces their capacity to organize politically to protect their rights of disposition, then serious problems will arise. In seeking to patent the material they “mine,” the bio-prospectors will have opened a sort of final colonialism, contained here in a chiasmus: from control over the raw material of nature to control over the nature of raw materials."
Posts: 5905 | From: The Hammer | Registered: Aug 2008
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-------------------- The Complete Picture of the Past tells Us what Not to Repeat Posts: 7516 | From: Somewhere on Earth | Registered: Jan 2008
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-------------------- Note: I am not an "Egyptologist" as claimed by some still bitter, defeated, trolls creating fake profiles and posts elsewhere. Hapless losers, you still fail. My output of hard data debunking racist nonsense has actually INCREASED since you began.. Posts: 5905 | From: The Hammer | Registered: Aug 2008
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posted
^ Why is this another thread? Can't the previous thread be continued?? By the way, the erroneous racialism of Sforza cannot take away from the fact of uniparental genetic markers or lineages showing African ancestry among both Southwest Asians and Europeans. So the question is where do these Euros get off talking about so-called "caucasoid" admixture in Africans??
Posts: 26239 | From: Atlanta, Georgia, USA | Registered: Feb 2005
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Thank you zarahan for this highly informative post. I think MacEachern must be one of a very few people in genetics now familiarized enough with the history of African popoulations and its problems to be studying or analyzing their genetics.
The below passage you quoted sums up the problem that has been occuring in the study of African genetics since its inception.
A lack of knowledge of the history of the people being dealt with.
"This claimed association of Khoisan people with “Caucasoids” is quoted in more recent works on genetics and history in Africa, among them the work by Passarino et al. (1998) on Ethiopian populations. This latter paper exhibits the same reliance upon inappropriate sources as does Cavalli-Sforza et al., with for example use of a 1964 Encyclopedia Britannica article as a primary reference on the prehistory of Ethiopia."
Cavalli-Sforza's interpretation of certain Africans was merely a genetic version of "hamitic Mediterranean" theory.
Posts: 4226 | From: New Jersey, USA | Registered: Mar 2007
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posted
If you don't like the terms "Negroid" and "Caucasoid" simply replace those words with "African" and "European" and proceed with what you planned to say -lioness tip
Posts: 42921 | From: , | Registered: Jan 2010
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posted
I am reading this book right now. All the points are very valid but the book is still a very good read.
Posts: 2463 | From: New Jersey USA | Registered: Dec 2007
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