Saturday, August 1, 2015

Guess who first came to America?


Semang from the Malayan Peninsula, Wikicommons

 

Before the Europeans came, the Americas were settled by three waves of people from northeast Asia: the oldest wave beginning some 12,000 to 15,000 years ago, which gave rise to most Amerindians, and two later waves, which gave rise respectively to the Athapaskan and Inuit peoples of northern Canada and Alaska. That's the conventional view.

Kennewick Man. An earlier form of Northeast Asian?

There is growing evidence, however, for earlier waves of settlement. There's Kennewick Man, who lived nine thousand years ago in the American northwest and who looked more European than Amerindian, the closest match being the Ainu of northern Japan. He also looked a lot like Patrick Stewart.

Nonetheless, a DNA study has found him to be closer to Amerindians than to any other existing population in the world (Rasmussen et al., 2015). He was apparently descended from the same Northeast Asians who would later become today's Native Americans. Those earlier Northeast Asians looked more European because they lived closer to the time when these two groups were one and the same people. It may be that the Ainu best preserve the appearance of this ancestral population that would later develop into present-day Europeans, East Asians, and Amerindians.

But why would Kennewick Man be closer anatomically to an Ainu while being closer genetically to an Amerindian? The answer is that the genes that shape our anatomy are a tiny subset of the entire genome. Most genes are of low selective value, often being junk DNA, so they change at a steady rate through random processes. Taken as a whole, the genome thus provides a "clock" that can measure how long two populations have been moving apart since their common ancestors. Genealogically speaking, Kennewick Man is closer to present-day Native Americans than he is to the Ainu. Anatomically speaking, the reverse is true ... probably because his ancestors had escaped the extreme Ice Age conditions that affected northeast Asia 20,000 - 15,000 years ago by retreating to an ice age refugium on the Northwest Pacific Coast. The Ainu may have similarly sat out the Ice Age in another refugium on the other side of the Pacific.

[...]  ancient plant and animal remains found on several offshore islands provide evidence that some areas of land on the outer coast remained unglaciated and habitable during the Ice Age. These ice-free areas are called refugia, and evidence for their existence has been found off the Pacific coast from Alaska to southern British Columbia.

Although there is no direct evidence for human occupation of these refugia during the mid-glacial period, it is clear that a chain of habitable environments existed along the Pacific Northwest Coast, and that these environments could have supported people as they made their way down the coast.

If people moved down the West Coast, and then into the interior from there, where and when did this inward movement occur? Is there any archaeology suggesting that populations on the coast began moving inland? 

A few sites from the interior areas of Washington State, Oregon and Idaho may demonstrate this. Stemmed projectile points are found in a site along the Snake River in Washington State, with dates ranging from 8,800 to 10,800 years ago. Another site in south-central Oregon, Fort Rock Cave, contained a layer of gravel that had two obsidian points within it. Dates from this layer are as old as 13,000 years BP. Wilson Butte Cave from Idaho also contains human made artifacts dating to between 14,500 and 13,000 years ago. Perhaps these sites are examples of early people moving in-land; however the small number of sites uncovered so far makes it hard to determine definitively whether the early settlers came from the coast, or from the east. (VMC, 2005)

Kennewick Man may thus have been part of an earlier wave of people moving into the Americas, which was long confined to the coastal Northwest. With the end of the ice age, circa 12,000 years ago, another wave of settlement opened up via an ice-free corridor running from Alaska to Montana along the eastern side of the Rockies. This second wave, associated with the Clovis culture, brought more people than the first one and ultimately contributed the most to present-day Amerindians.

There were humans even earlier

But the story doesn't end here. There seems to have been another people before the Amerindians and even before the older and more European-like Kennewick humans. A recent study has looked at the gene pool of Native Americans from the Amazon. Not surprisingly, most of it closely matches that of Northeast Asians. But a tiny portion is like what we see in the natives of Australia, Papua New Guinea, and Melanesia (Skoglund et al., 2015)

It would be easy to dismiss this finding as a fluke, were it not for other evidence of a very different people who once lived in the Amazon basin 16,000 to 9,000 years ago (Roosevelt et al., 1996). While overlapping in time with the Clovis culture, they show none of its emphasis on big game hunting, as seen in the well-known Clovis projectile point and other hunting tools. In fact, they were much like tropical foragers of central Africa or Papua-New Guinea. And their earliest remains precede the Clovis culture by at least three thousand years, even though the Amazon rain forest should have been one of the last areas to be penetrated by former denizens of the Arctic.

There's more. A site in central Brazil has yielded several skulls dated to between 8,200 and 9,500 years ago. They don't look at all Amerindian: 

[...] they exhibit strong morphological affinities with present day Australians and Africans, showing no resemblance to recent Northern Asians and Native Americans. These findings confirm our long held opinion that the settlement of the Americas was more complicated in terms of biological input than has been widely assumed. The working hypothesis is that two very distinct populations entered the New World by the end of the Pleistocene, and that the transition between the cranial morphology of the Paleoindians and the morphology of later Native Americans, which occurred around 8-9 ka, was abrupt. [...] The similarities of the first South Americans with sub-Saharan Africans may result from the fact that the non-Mongoloid Southeast Asian ancestral population came, ultimately, from Africa, with no major modification in the original cranial bau plan of the first modern humans. (Neves et al., 2003).

Similar findings have emerged from analysis of skulls from Mexico dated to between 9,000 and 11,000 years ago and skulls from Colombia dated to between 7,500 and 8,300:

[...] only 6 out of 25 comparisons displayed in Table 3 tend to tie an early Mexican specimen to an Amerindian sample. Conversely, 19 of the 25 comparisons reflect the greatest similarity to Africans (6/25), Paleoindians (5/25), Australians (3/25), Polynesians (3/25), South Asians (1/25), or the Ainu (1/25). When first-place positions are explored, all five are circum-Pacific, either recent or early. Among second-place positions, 4 out of 5 are circum-Pacific, and the remaining one is African.

[...] To summarize, analyses of individual skulls against reference samples suggest that the early Mexican fossils studied do not share a common craniofacial morphology with Amerindians or East Asians, as reported elsewhere for South Paleoindians, some North Paleoindian specimens […] and some modern groups like Fuegian-Patagonians and the Pericúes from Baja California.

[...] This study does not support continuity between Early and Late Holocene groups in the Americas: Archaic remains from Colombia are not an intermediate point between Paleoamericans and modern groups. Moreover, the data presented here support the idea that the first settlers of the New World preceded the origin of the more specialized morphology observed in modern populations from Northeast Asia. (Gonzalez-Jose et al., 2005)

This shouldn't be too surprising. Here and there in Southeast Asia we find relic groups of small, dark-skinned, and woolly-haired hunter-gatherers: the Andamanese of India, the Semang of Malaysia, and the Aeta of the Philippines. They used to predominate throughout that region as late as four thousand years ago. Farther back in time, in prehistory, they may have also lived farther north, perhaps at one point the entire East Asian littoral ... and from there into the Americas. This would be before the last ice age, and probably before another wave of modern humans moved into northern Eurasia.

The past is another country, just as the future is another country. We unthinkingly assume that a place has always been home to a people who look a certain way, behave a certain way, and organize their lives a certain way. This is as untrue for the Americas as it is for anywhere else. Going back in time, we see people who look more and more ancestral not only to Amerindians but also to Europeans and East Asians. Eventually, those ancestral Eurasians disappear and we meet a very different sort of human.

What happened to those first inhabitants of the Americas? Did they go peacefully into the night when the newcomers arrived, retreating farther and farther into more remote areas? Or did the two groups fight it out? There was probably a range of scenarios—perhaps small numbers of newcomers initially worked out a modus vivendi with the natives, which later broke down as they became more and more numerous. In any case, the process matters less than the result. Those first Americans went into the night, peacefully or not.

References

Gonzalez-Jose, R., W. Neves, M. Mirazon Lahr, S. Gonzalez, H. Pucciarelli, M. Hernandez Martinez, and G. Correal. (2005). Late Pleistocene/Holocene Craniofacial Morphology in Mesoamerican Paleoindians: Implications for the Peopling of the New World, American Journal of Physical Anthropology, 128, 772-780
http://www.hectorpucciarelli.com.ar/pdf/112.AJPA-Gonzalez-Jose%20et%20al.%202005(b).pdf

Neves, W.A., A. Prous, R. Gonzalez-Jose, R. Kipnis, and J. Powell. (2003). Early Holocene human skeletal remains from Santana do Riacho, Brazil: implications for the settlement of the New World, Journal of Human Evolution, 45, 19-42.
http://www.museunacional.ufrj.br/arqueologia/docs/papers/Prous/nevesprous2003skeletalremains.pdf 

Rasmussen, M., M. Sikora, A. Albrechtsen, T. Sand Korneliussen, J.Victor Moreno-Mayar, G. David Poznik, C.P.E. Zollikofer, M.S. Ponce de Leon, M.E. Allentoft, I. Moltke, H. Jonsson, C. Valdiosera, R.S. Malhi, L. Orlando, C.D. Bustamante, T.W. Stafford Jr. D.J. Meltzer, R. Nielsen, and E. Willerslev. (2015). The ancestry and affiliations of Kennewick Man. Nature, early view
http://www.nature.com/nature/journal/vnfv/ncurrent/full/nature14625.html 

Roosevelt, A.C., M. Lima da Costa, C. Lopes Machado, M. Michab, N. Mercier, H. Valladas, J. Feathers, W. Barnett, M. Imazio da Silveira, A. Henderson, J. Silva, B. Chernoff, D.S. Reese, J.A. Holman, N. Toth, and K. Schick. (1996). Paleoindian cave dwellers in the Amazon: The peopling of the Americas, Science, 272, 373-384.
http://www.researchgate.net/profile/William_Barnett3/publication/235237012_Paleoindian_Cave_Dwellers_in_the_Amazon_The_Peopling_of_the_Americas/links/00b7d524c6599de57c000000.pdf 

Skoglund, P., S. Mallick, M.C. Bortolini, N. Chennagiri, T. Hunemeier, M.L. Petzl-Erler, F. Mauro Salzano, N. Patterson, and D. Reich. (2015). Genetic evidence for two founding populations of the Americas, Nature, early view.
http://www.nature.com/nature/journal/vnfv/ncurrent/full/nature14895.html 

VMC (2005). A journey to a new land. Coastal Refugia
http://www.sfu.museum/journey/an-en/postsecondaire-postsecondary/refuges_cotiers-coastal_refugia

Saturday, July 25, 2015

Survival of the nicest-smelling?


 
The Perfume Maker, Rudolf Ernst (1854-1932) (Wikicommons)

 

It has long been known that we vary not only in our sensitivity to different smells but also in our preferences for them—the degree to which they seem pleasant or unpleasant. This variability often contains a large genetic component (Gross-Isseroff et al., 1992; Karstensen and Tommerup, 2012; Keller et al., 2007; Keller et al., 2012; Weiss et al., 2011). In the case of one odor, a single gene explains over 96% of the variability in smell sensitivity (Jaegar et al., 2013). A twin study has similarly found two odorants to be 78% and 73% heritable (Gross-Isseroff, 1992). This hardwiring is selective, however, because sensitivity to other odors can show little or no heritable variation (Hubert et al., 1980). There is also selective hardwiring in smell preferences. Different individuals will perceive androstenone, for instance, as offensive ('sweaty, urinous'), pleasant ('sweet, floral'), or odorless (Keller et al., 2007). It seems that selection has produced specific algorithms in the human brain for specific smells and that these algorithms can differ from one individual to the next (Keller et al., 2007; Knaapila et al., 2012).

This genetic variability exists between men and women, and also between age groups (Keller et al., 2012). Does it also exist between different human populations? The sense of smell does seem to matter more in some than in others, particularly hunter-gatherers:

People pay attention to smells when they are important to their daily lives and are not just part of the sensory and emotional background. This is certainly the case with the Umeda of New Guinea: in a tropical rainforest scent plays as important a role as sight in terms of spatial orientation. The Waanzi in southeast Gabon use odors daily in fishing, hunting, and gathering, thanks to a kind of 'olfactory apprenticeship' in family life and rituals of initiation. In Senegal, the Ndut are even more skillful: they are able to distinguish the odors of the different parts of plants and they are able to give a name to these odors. In our society, of course, most of us are incapable of this. (Candau, 2004)

For hunter-gatherers farther away from the tropics, the sense of smell matters less because the land supports a lower diversity of plant species and has less plant life altogether per unit of land area. Parallel to this north-south trend, more food comes from hunting of game animals and less from gathering of plant items. The end point is Arctic tundra, where opportunities for gathering are limited even in summer and where most food takes the form of meat. There, the senses of sight and sound matter more, being of greater value for long-range detection and tracking of game animals.

Candau (2004) sees these differences between human groups as evidence for "cultural influences" rather than "genetic inheritance." The two are not mutually exclusive: culture itself can select for some heritable abilities over others. On this point, it may be significant that different human groups continue to show differences in smell sensitivity and preference long after their ancestors had moved to very different environments. Thus, in a study from New York City, Euro-American and African American participants were exposed to a wide range of odors. It was found that the two groups differed in their pleasantness rating of 18 of the 134 stimuli, generally floral or vegetative odors. Moreover in 14 of the 18, the African Americans were the ones who responded more positively (Keller et al., 2012).

In addition, the African Americans responded more readily to aromatic metabolites of the male hormone testosterone, i.e., androstadienone and androstenone. The authors note: "This is consistent with the finding from the National Geographic Smell Survey, which found that African respondents were more sensitive to androstenone than American respondents. This difference is undoubtedly at least partially caused by the fact that the functional RT variant of OR7D4 is more common in African-Americans than in Caucasians" (Keller et al., 2012).

Gene-culture coevolution during historic times

This coevolution did not stop with hunter-gatherers. Beginning 10,000 years ago, some of them became farmers and that change set off a lot of other changes: population growth, land ownership, creation of a class system, social inequality on a much greater scale, year-round settlement in villages and then in towns and cities ... And on and on. We entered new environments—not natural ones of climate and vegetation, but rather human-made ones.

These environments offered us new olfactory stimuli: salves, perfumes, incense, scented oils, aromatic baths ... Havlicek and Roberts (2013) argue that our sense of smell coevolved with human-made fragrances and that this coevolution went on for the longest in the Middle East and South Asia, where the use of perfumes is attested as early as the fourth millennium B.C. (Wikipedia, 2015). A sort of positive feedback then developed between use of these fragrances and praise of them in prose, song, and poetry, the two reinforcing each other and thereby strengthening the pressure of selection. This may be seen in the Bible:

The Hebrew Song of Songs furnishes a typical example of a very beautiful Eastern love-poem in which the importance of the appeal to the sense of smell is throughout emphasized. There are in this short poem as many as twenty-four fairly definite references to odors,—personal odors, perfumes, and flowers,—while numerous other references to flowers, etc., seem to point to olfactory associations. Both the lover and his sweetheart express pleasure in each other's personal odor. 

"My beloved is unto me," she sings, "as a bag of myrrh
That lieth between my breasts;
My beloved is unto me as a cluster of henna flowers
In the vineyard of En-gedi."

And again: "His cheeks are as a bed of spices [or balsam], as banks of sweet herbs." While of her he says: "The smell of thy breath [or nose] is like apples." (Ellis, 1897-1928)

In the 9th century the Arab chemist Al-Kindi wrote the Book of the Chemistry of Perfume and Distillations, which contained more than a hundred recipes for fragrant oils, salves, and aromatic waters (Wikipedia, 2015). Today, the names of our chief perfumes are often of Arabic or Persian origin: civet, musk, ambergris, attar, camphor …

Finally, the use of perfumes, like kissing and cosmetics in general, moved the center of sexual interest away from the genitals and toward the face, thereby creating a second channel of arousal:

[...] the focus of olfactory attractiveness has been displaced. The centre of olfactory attractiveness is not, as usually among animals, in the sexual region, but is transferred to the upper part of the body. In this respect the sexual olfactory allurement in man resembles what we find in the sphere of vision, for neither the sexual organs of man nor of woman are usually beautiful in the eyes of the opposite sex, and their exhibition is not among us regarded as a necessary stage in courtship. The odor of the body, like its beauty, in so far as it can be regarded as a possible sexual allurement, has in the course of development been transferred to the upper parts. The careful concealment of the sexual region has doubtless favored this transfer. (Ellis, 1897-1928)

Differences between human populations?

To recapitulate, we humans vary a lot in the degree to which we have been exposed to perfumes and to a perfume-friendly culture, a possible analogy being the degree to which we have been exposed to alcoholic beverages. There may thus have been selection against individuals whose own smell preferences or body chemistry failed to match the perfumes available, this selection being not only stronger in some populations but also qualitatively different:

[...] individual communities vary considerably in the substances they employ for perfume production (in most of the speculations below we deliberately ignore recent trends such as technological advancement in global transfer of goods and production of synthetic chemicals used in perfumery: these phenomena appeared only very recently and one might not expect their immediate effect on biological evolution which operates on a much longer time scale). The absence of a specific ingredient in the perfumes of a particular community could be due to the following reasons: (1) the source of the odour is unavailable in the area and is not traded from neighbours. For example, we know that aromatic plants were an important commodity in trading networks in Ancient Egypt or Greece, but some of the scents routinely employed in that era in India were rare or absent in Mediterranean cultures. (2) The community is constrained by a technology. Some of the aromas can be extracted only using a specific technology which might not be available for or discovered by the particular community. In ancient Greece, for instance, ethanol distillation was not used and perfumers instead used mechanic extraction or enfleurage (Brun 2000). (3) Particular scents or their source (e.g. a particular plant) are believed to be inappropriate for body adornment. Such beliefs might stem from religious considerations.

[...] considering that only some scent ingredients will complement particular body odours (i.e. particular genotypes) and that a particular community employs only a restricted variety of scents for perfuming, it is plausible that some individuals may not be able to select a perfume which complements their body odour and may therefore suffer a social disadvantage. In the long run, the frequency of genotypes of such individuals would decrease in the particular community. (Havlicek and Roberts, 2013)

It is disappointing that Havlicek and Roberts do not develop this argument further with plausible evidence for such gene-culture coevolution. For instance, Hall et al. (1968) discussed how smell and touch hold greater importance for Arabs than for Americans. This point has likewise been remarked upon with respect to the Gulf countries:

The importance of good smell in Qatari homes is inherent in the requirement of cleanness and purity (taharah) in Islam, both physical and spiritual (Sobh and Belk, 2010). Purity, cleanness, and good smell are central to Muslims everywhere in the world, but the obsession with perfuming bodies and homes is something of a fetish in Gulf countries and is very prominent in Qatar. (Sobh and Belk, 2011)

This heightened smell sensitivity is all the more striking because plant life is less abundant and less diverse in the Middle East, certainly in comparison with the tropics. It seems unlikely, then, that it had been acquired during the hunter-gatherer stage of cultural evolution, being instead a later development, possibly through coevolution with the development of perfumes in historic times.

References 

Candau, J. (2004). The olfactory experience: constants and cultural variables, Water Science & Technology, 49, 11-17.
https://halshs.archives-ouvertes.fr/halshs-00130924/  

Ellis, H. (1897-1928). Studies in the Psychology of Sex, vol. IV, Appendix A. The origins of the kiss.
https://www.gutenberg.org/files/13613/13613-h/13613-h.htm 

Gross-Isseroff, R., D. Ophir, A. Bartana, H. Voet, and D. Lancet. (1992). Evidence for genetic determination in human twins of olfactory thresholds for a standard odorant, Neuroscience Letters, 141, 115-118.
http://www.sciencedirect.com/science/article/pii/030439409290347A 

Hall, E.T., R.L. Birdwhistell, B. Bock, P. Bohannan, A.R. Diebold, Jr., M. Durbin, M.S. Edmonson, J.L. Fischer, D. Hymes, S.T. Kimball, W. La Barre, F. Lynch, J.E. McClellan, D.S. Marshall, G.B. Milner, H.B. Sarles, G. L Trager, and A.P. Vayda  (1968). Proxemics, Current Anthropology, 9, 83-108
http://www.jstor.org/stable/2740724?seq=1#page_scan_tab_contents 

Havlícek, J., and S.C. Roberts (2013). The Perfume-Body Odour Complex: An Insightful Model for Culture-Gene Coevolution? Chemical Signals in Vertebrates, 12, 185-195.
http://www.scraigroberts.com/uploads/1/5/0/4/15042548/2013_csiv_perfume.pdf 

Hubert, H.B., R.R. Fabsitz, M. Feinleib, and K.S. Brown. (1980). Olfactory sensitivity in humans: genetic versus environmental control, Science, 208, 607-609.
http://www.sciencemag.org/content/208/4444/607.short 

Jaeger, S.R., J.F. McRae, C.M. Bava, M.K. Beresford, D. Hunter, Y. Jia et al. (2013). A Mendelian Trait for Olfactory Sensitivity Affects Odor Experience and Food Selection, Current Biology, 23, 1601 - 1605
http://www.cell.com/current-biology/abstract/S0960-9822(13)00853-1?_returnURL=http%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0960982213008531%3Fshowall%3Dtrue 

Knaapila, A., G. Zhu, S.E. Medland, C.J. Wysocki, G.W. Montgomery, N.G. Martin, M.J. Wright, D.R. Reed. (2012). A genome-wide study on the perception of the odorants androstenone and galaxolide, Chemical Senses, 37, 541-552.
http://www.researchgate.net/profile/Danielle_Reed2/publication/221859158_A_genome-wide_study_on_the_perception_of_the_odorants_androstenone_and_galaxolide/links/02e7e52b367564a573000000.pdf

Karstensen, H.G. and N. Tommerup. (2012). Isolated and syndromic forms of congenital anosmia, Clinical Genetics, 81, 210-215. 

Keller, A., M. Hempstead, I.A. Gomez, A.N. Gilbert and L.B Vosshall. (2012). An olfactory demography of a diverse metropolitan population, BMC Neuroscience, 13, 122
http://www.biomedcentral.com/1471-2202/13/122/ 

Keller, A., H. Zhuang, Q. Chi, L.B. Vosshall, and H. Matsunami. (2007). Genetic variation in a human odorant receptor alters odour perception, Nature, 449, 468-472
http://vosshall.rockefeller.edu/reprints/KellerMatsunamiNature07.pdf

Sobh, R. and R. Belk. (2011). Domains of privacy and hospitality in Arab Gulf homes, Journal of Islamic Marketing, 2, 125-137
http://www.researchgate.net/profile/Rana_Sobh/publication/241699027_Domains_of_privacy_and_hospitality_in_Arab_Gulf_homes/links/54a1374b0cf257a63602614b.pdf

Weiss, J., M. Pyrski, E. Jacobi, B. Bufe, V. Willnecker, B. Schick, P. Zizzari, S.J. Gossage, C.A. Greer, T. Leinders-Zufall, et al. (2011). Loss-of-function mutations in sodium channel Nav1.7 cause anosmia, Nature, 472, 186-190. 

Wikipedia (2015). Perfume
https://en.wikipedia.org/wiki/Perfume 

Saturday, July 18, 2015

Not everyone does it


 
Un homme et une femme, 1891, Stephan Sinding (1846-1922). Almost as fun as sex.

 

All humans love to kiss, so kissing must go back to early hominids and even chimps and bonobos. This is how ethologists and evolutionary psychologists think when they write about the subject.

Just one thing. Even in historic times not all humans loved to kiss. Far from arising millions of years in the past, kissing seems to have arisen no earlier than 40,000 years ago, when modern humans began to enter northern Eurasia.

So concludes a recent cross-cultural study:

We found only 77 out of 168 (46%) cultures in which the romantic-sexual kiss was present. Significantly, no ethnographer working with Sub-Saharan African, New Guinea, or Amazonian foragers or horticulturalists reported having witnessed any occasion in which their study populations engaged in a romantic-sexual kiss. However, kissing appears to be nearly ubiquitous among 9 of the 11 foragers living in Circum-Arctic region (i.e., northern Asia and North America). The concentration of kissing among Circum-Arctic foragers, for which we do not have a satisfactory explanation other than invoking cultural diffusion, stands in stark contrast to its equally striking absence among foragers in other cultural regions. (Jankowiak et al., 2015)

This is not the first study to deny the universality of kissing, although scholars have tended to place its origin in the civilizations of the Mediterranean, the Middle East, and South Asia (Hawley, 2007; Hopkins, 1907). The English sexologist Havelock Ellis argued that kissing began with "civilized man": 

It is only under a comparatively high stage of civilization that the kiss has been emphasized and developed in the art of love. Thus the Arabic author of the Perfumed Garden, a work revealing the existence of a high degree of social refinement, insists on the great importance of the kiss, especially if applied to the inner part of the mouth, and he quotes a proverb that "A moist kiss is better than a hasty coitus." Such kisses, as well as on the face generally, and all over the body, are frequently referred to by Hindu, Latin, and more modern erotic writers as among the most efficacious methods of arousing love. (Ellis,1897-1928)

It may be that kissing originated in prehistory among the hunter-gatherers of northern Eurasia and then spread south, where it reached its full flowering in a milieu that idealized it in prose, poetry, and painting. A kind of positive feedback thus developed between the practice and the ideal.

Then, at a later date, it became less common in northern Europe because of the moral climate that followed the Reformation, having been previously very common. When the Greek scholar Demetrios Chalkokondyles (1423-1511) visited England, he was surprised by its ubiquity:

As for English females and children, their customs are liberal in the extreme. For instance, when a visitor calls at a friend's house, his first act is to kiss his friend's wife; he is then a duly-installed guest. Persons meeting in the street follow the same custom, and no one sees anything improper in the action. (Bombaugh, 1876, p. 33)

Another Greek traveler likewise remarked a century later:

The English manifest much simplicity and lack of jealousy in their customs as regards females; for not only do members of the same family and household kiss them on the lips with complimentary salutations and enfolding of the arms around the waist, but even strangers, when introduced, follow the same mode, and it is one which does not appear to them in any degree unbecoming. (Bombaugh, 1876, p. 33)

Similar comments were made by Erasmus (1467-1536):

If you go to any place, you are received with a kiss by all; if you depart on a journey, you are dismissed with a kiss; if you return, the kisses are exchanged. Do they come to visit you, a kiss is the first thing; do they leave you, you kiss them all around. Do they meet you anywhere, kisses in abundance. In short, wherever you turn, there is nothing but kisses. Ah, Faustus, if you had once tasted the tenderness, the fragrance of these kisses, you would wish to stay in England, not for ten years only, but for life. (Bombaugh, 1876, p. 34)

Kissing then fell into decline among the English; so much so, that frequent public displays became seen as a continental thing. Nonetheless, it remained much more common than in other parts of the world, particularly East Asia and sub-Saharan Africa. This difference amused travelers as late as the 19th century:

An American naval officer, who had spent considerable time in China, narrates an amusing experience of the ignorance of the Chinese maidens of the custom of kissing. Wishing to complete a conquest he had made of a young mei jin (beautiful lady), he invited her—using the English words—to give him a kiss. Finding her incomprehension of his request somewhat obscure, he suited the action to the word and took a delicious kiss. The girl ran away into another room, thoroughly alarmed, exclaiming, "Terrible man-eater, I shall be devoured." (Bombaugh, 1876, p. 80)

For the same time period, Havelock Ellis noted: "Kisses, and embraces are simply unknown in Japan as tokens of affection" with the exception of mothers hugging and kissing their infants. Similarly, "among nearly all of the black races of Africa lovers never kiss nor do mothers usually kiss their babies." He then went on to argue that the romantic kiss evolved out of this maternal kissing, which seems more or less universal.

With the globalization of culture through movies, magazines, and other media, kissing has been spread to the four corners of the earth. Clearly, we can all do it and enjoy doing it to some extent. But I don't think we all share the same urge to do it.

Gene-culture coevolution?

Don't laugh. Even religiosity is partly genetic, so why not the desire to kiss and be kissed? What little we know about the subject comes from studies of compulsive kissing syndrome, where a lesion to the right temporal lobe (associated with epilepsy or glioma) causes an uncontrollable urge to kiss anyone independently of sexual interest (Mendez and Shapira, 2014; Mikata et al., 2005; Ozkara et al., 2004). This compulsion differs from other disorders where increased kissing results from loss of sexual inhibition and is targeted at sexually desirable individuals. The brain may thus have a pre-formed circuit that triggers the desire to kiss. In short, kissing is not solely learned. It has an innate component.

At first, this innate component would have been the same in all humans, back when kissing mainly happened between a mother and her infants. It then became more sexual and more important among the hunter-gatherers of northern Eurasia. Later still, in Europe and the Middle East, it developed into a second channel of sexual arousal almost on a par with the sex act itself.

As Havelock Ellis observed:

[...] there is certainly no such channel for directing nervous force into the sexual sphere as the kiss. This is nowhere so well recognized as in France, where a young girl's lips are religiously kept for her lover, to such an extent, indeed, that young girls sometimes come to believe that the whole physical side of love is comprehended in a kiss on the mouth; so highly intelligent a woman as Madam Adam has described the agony she felt as a girl when kissed on the lips by a man, owing to the conviction that she had thereby lost her virtue.

Sexual kissing initially arose through people pushing the envelope of phenotypic plasticity. This envelope in turn became part of the environment that people had to fit into. Those who couldn't, or wouldn't, were at a disadvantage and were bit by bit pushed out of the gene pool. Those who could, and would, took their place. New genetic variants thus arose and flourished, some to strengthen the new behavior and others to make it more pleasurable.

In this, and in many other ways, Man has created Man. We humans have shaped our environment, which in turn has shaped us, even in our genes. This point becomes clear only if one abandons the assumption, so dear to evolutionary psychology, that we stopped evolving back in the Pleistocene. We didn't. In fact, most of the interesting stuff has come about since then.

References 

Bombaugh, C.C. (1876). The Literature of Kissing, gleaned from history, poetry, fiction, and anecdote, Philadelphia: J.B. Lippincott & Co.
https://books.google.ca/books?id=p9lPAAAAYAAJ&printsec=frontcover&hl=fr&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false  

Ellis, H. (1897-1928). Studies in the Psychology of Sex, vol. IV, Appendix A. The origins of the kiss.
https://www.gutenberg.org/files/13613/13613-h/13613-h.htm 

Hawley, R. (2007). 'Give me a thousand kisses': the kiss, identity, and power in Greek and Roman antiquity, Leeds International Classical Studies, 6.5
http://pdf.thepdfportal.net/?id=123399 

Hopkins, E.W. (1907). The sniff-kiss in ancient India, Journal of the American Oriental Society, 28, 120-134.
http://www.jstor.org/stable/592764?seq=1#page_scan_tab_contents 

Jankowiak, W.R., S.L. Volsche, J.R. Garcia. (2015). Is the Romantic-Sexual Kiss a Near Human Universal? American Anthropologist, early view
http://onlinelibrary.wiley.com/wol1/doi/10.1111/aman.12286/abstract 

Mendez, M.F. and J.S. Shapira. (2014). Kissing or "Osculation" in Frontotemporal Dementia, The Journal of Neuropsychiatry & Clinical Neurosciences, 26, 258-261.
http://neuro.psychiatryonline.org/doi/full/10.1176/appi.neuropsych.13060139 

Mikati, M.A., Y.G. Comair, A.N. Shamseddine. (2005). Pattern-induced partial seizures with repetitive affectionate kissing: an unusual manifestation of right temporal lobe epilepsy. Epilepsy & Behavior, 6, 447-451
http://www.sciencedirect.com/science/article/pii/S1525505005000144 

Ozkara, C., H. Sarý, L. Hanoglu, et al. (2004). Ictal kissing and religious speech in a patient with right temporal lobe epilepsy, Epileptic Disorders, 6, 241-245
http://www.jle.com/fr/revues/epd/e-docs/ictal_kissing_and_religious_speech_in_a_patient_with_right_temporal_lobe_epilepsy__265692/article.phtml?tab=download&pj_key=doc_alt_2458

Saturday, July 11, 2015

The puzzle of European hair, eye, and skin color


 
Mary Magdalene, Frederick Sandys (1829-1904). Is the physical appearance of Europeans solely or even mainly an adaptation to climate?
 

The Russian online magazine Kultura VRN has published an article I wrote on the "puzzle of European hair, eye, and skin color." The following is the original English text.

 

Most humans have black hair, brown eyes, and brown skin. Europeans are different: their hair is also brown, flaxen, golden, or red, their eyes also blue, gray, hazel, or green, and their skin pale, almost like an albino's. This is particularly the case in northern and eastern Europeans. 

How did this color scheme come about? Perhaps the same genes that lighten skin pigmentation also affect hair and eye pigmentation. Yet the genes are different in each case. Our skin became white mainly through the replacement of one allele by another at three separate genes. Our hair acquired a diverse palette of colors through a proliferation of new alleles at another gene. Our eyes acquired a similar palette through similar changes at yet another gene.

This color scheme is puzzling in another way: it is stronger in women than in men. Women are naturally more variable than men in hair color, redheads in particular being more common. They are likewise more variable in eye color in those populations where blue eyes are common. Finally, throughout the world, women are fairer-skinned than men, as a result of cutaneous changes at puberty.

While women are more diversely colored in their hair and eyes, this greater diversity has a different cause in each case. In the case of hair color, women have more of the intermediate hues because the darkest hue (black) is less easily expressed. In the case of eye color, women have more of the intermediate hues because the lightest hue (blue) is less easily expressed.

If hair color and eye color diversified in ways that differ physiologically but are similar visually, then the common purpose of this diversity must be visual. Furthermore, in both cases, this diversity concerns visible features on or near the face—the focus of visual attention.

Sexual selection?

Why would a facial feature become more colorful in one sex than in the other? The likeliest reason is sexual selection, which occurs when one sex has to compete for the attention of the other. This kind of selection favors eye-catching colors that are either bright or novel.

Bright colors stay in memory longer. If we look at the hair and eye colors that arose in Europe, we see that they are brighter than the human norm of black hair and brown eyes. Hair is carrot red but not beet red. Eyes are sky blue but not navy blue.

Novel colors hold attention longer. Attraction to novelty may explain how the European palette of hair and eye colors came into being. First, a new color would appear by mutation and be initially rare and novel. Second, its novelty would attract attention and increase one's chances of mating, with the result that the color would become more common in succeeding generations. Third, attention would now shift toward rarer and more novel colors that had recently appeared by mutation. All in all, it was this fascination with novelty that caused the number of hair and eye colors to increase steadily over time, once sexual selection had become strong enough.

This novelty effect appears in a study on male preferences for female hair color. Men were shown a series of photos of attractive blondes and brunettes, and they were asked to choose the one they most wanted to marry. It turned out that the scarcer the brunettes were in the series, the likelier any one brunette would be chosen. Another study likewise found that Maxim cover girls are much more often light blonde or dark brown than the usual dark blonde or light brown of real life.

A preference will become a choice only if one has a choice. This is the principle of sexual selection: one sex is in a better position to choose than the other. In most mammalian species, females are in a better position because they can choose among a larger number of males on the mate market. This is because the latter are almost always available for mating, whereas females are unavailable during pregnancy and the period of infant care. Males thus tend to be polygamous.

In early human societies that lived from hunting and gathering, the incidence of polygamy varied with latitude. It was highest in the tropics, where a woman could gather food year-round and feed herself and her children with little male assistance. This self-reliance made it easier for her mate to look for another woman.

Beyond the tropics, women were less self-reliant, particularly during winter when they could no longer gather food and depended on meat from their spouses. This dependence increased with longer winters at higher latitudes. In the Arctic, only a very able hunter could support a second wife. 

Higher latitudes meant not just fewer men on the mate market but also fewer men altogether. Because women could not supply as much food and because the land supported less wildlife, men had to hunt for a longer time over longer distances, with the result that more of them died from falls, drowning, starvation, and cold. Women thus faced a competitive mate market and strong sexual selection. This was especially so on the continental steppe-tundra of the sub-Arctic, where almost all food came from long-distance hunting. 

During the last ice age, this steppe-tundra covered more territory, stretching from the plains of Europe to Alaska. But it was continuously inhabited only at its western end. The climate was milder there because the Scandinavian icecap had pushed the steppe-tundra to the south and because the Atlantic Ocean provided warmth and moisture. These conditions favored a lush growth of grasses, mosses, lichens, and low shrubs, which supported large herds of herbivores and, in turn, a large human population. The climate was less favorable east of the Urals, in Asia, where the steppe-tundra was colder and drier because it was located farther north and farther from the Atlantic's moderating influence. As a result, the human population was smaller and more vulnerable to extinction, particularly during the glacial maximum.

In sum, the European steppe-tundra was a singularity among the many environments that confronted early humans as they spread around the world. Food was abundant but accessible only to males of hunting age, whose ranks were thinned by hunting deaths. A surplus of single women developed, partly because men were fewer in number and partly because men could not easily bear the cost of providing for a second wife and her children. Women thus had to compete against each other for a smaller number of potential mates, the result being strong sexual selection for those women with eye-catching characteristics.

Ancient DNA

Today, this is the same region where the skin is whitest and the hair and eyes most diversely colored. Here, too, the earliest evidence of this color scheme has been found in ancient DNA from human remains. Initially, it was thought that blue eyes arose among the hunter-gatherers of the Mesolithic and white skin among the farmers of the Neolithic. This view has been challenged by genetic evidence of white skin, red hair, blonde hair, and blue eyes in the remains of Mesolithic hunter-gatherers from Scandinavia and Russia. It seems that some people already had the European color scheme at that early date, but only in the north and east of Europe.

But when exactly did this color scheme develop? Probably earlier still—sometime between the earliest Mesolithic evidence (8,000 years ago) and Kostenki Man (circa 37,000 years ago), who still had dark skin, dark eyes, and an African facial shape. As we retrieve more ancient DNA, we may narrow this timeframe, perhaps to the last ice age (circa 10,000 to 25,000 years ago) when steppe-tundra covered the plains of northern and eastern Europe ... and where men were a critical resource in limited supply.

That is a big change over a short time. If sexual selection had not been the cause, what else could have been? The need to adapt to weaker sunlight and a colder climate? Why, then, did this evolution not happen among indigenous peoples who live just as far north in Asia and North America? In any case, why would a northern climate favor a proliferation of new hair and eye colors?

Future research

We cannot go back in time to see why early Europeans changed so fast and so radically. But we can question "witnesses" from that time. As we have seen, one witness is ancient DNA, and this research is ongoing.

Another witness is sex linkage. If sexual selection had acted on early European women, it should have directly modified their physical appearance. Since most genes have little or no sex linkage, this selection would have also indirectly modified the appearance of early European men. But there should still be some signs of sex linkage. We know, for example, that blue eyes are associated with a more feminine face shape. Other examples probably remain to be found.

Finally, there is the witness of culture. Single women, typically virgins, hold an unusual importance in the myths, folklore, and traditions of Europe. In this, we may see an echo of a time when many women never married and became oriented toward communal tasks, such as tending camp fires or acting as seers, sibyls, oracles, and the like. That period of prehistory may have influenced the subsequent course of cultural evolution, thereby giving women a greater role in society at large than they otherwise would have.

Reference

Frost, P. (2015).Загадка цвета кожи, волос и глаз у европейцев, Куьтура ВРН, July 7, translated by Dr. Yuri Lozotsev.
http://culturavrn.ru/world/15780

Saturday, July 4, 2015

The Jews of West Africa?


Bronze vessel in the form of a snail shell, 9th century, Igbo-Ukwu (Wikicommons). The Igbo developed metallurgy much earlier than the rest of West Africa.

 

There has been much talk here about Chanda Chisala's article "The IQ gap is no longer a black and white issue." Much of the article focuses on the Igbo (known also as Ibo), a people who live in the Niger Delta and "are well known to be high academic achievers within Nigeria." In the United Kingdom, their children do as well in school as Chinese and Indian students:

The superior Igbo achievement on GCSEs is not new and has been noted in studies that came before the recent media discovery of African performance. A 2007 report on "case study" model schools in Lambeth also included a rare disclosure of specified Igbo performance (recorded as Ibo in the table below) and it confirms that Igbos have been performing exceptionally well for a long time (5 + A*-C GCSEs); in fact, it is difficult to find a time when they ever performed below British whites. (Chisala, 2015)

The Igbo have long been known as achievers, particularly in business. Whereas trade is largely women's work in the rest of West Africa, it is dominated by Igbo of both sexes in Nigeria.

[...] In study after study, it has been documented that the Ibo, through conflict and mobility, have been very successful in enterprise. Indeed, a major study argued that the Ibo have a very high need for achievement in the business world. Still another study showed that the majority of entrepreneurs in the sample were Ibo. (Butler, 1997, p. 178)

Sabino and Hall (1999) describe them as being “competitive, individualistic, status-conscious, antiauthoritarian, pragmatic, and practical—a people with a strongly developed commercial sense.” In colonial-era literature, they were often called "the Jews of West Africa" (see note).

Prehistory

How did the Igbo become so entrepreneurial? It's possible that their location in the Niger Delta predisposed them to be go-betweens in trade between coastal and interior peoples. Similar assemblages of glass beads, many of Egyptian origin and dating to the 9th and 14th centuries, have been recovered from the Niger Delta and eastern Mali, indicating that the Niger acted as a conduit of trade from the Atlantic coast to the Sahel and thence to the Middle East (Davison,1972; Insoll and Shaw, 1997).

Archaeological sites in the Niger Delta show that advanced economic development began much earlier there than elsewhere in West Africa. This is seen in early use of metallurgy. At one metallurgical complex, dated to 765 BC, iron ore was smelted in furnaces measuring a meter wide. The molten slag was drained through conduits to pits, where it formed blocks weighing up to 43-47 kg. The operating temperatures are estimated to have varied between 1,155 and 1,450 degrees C (Holl, 2009). Some radiocarbon dates for iron smelting in this region go back to 2000 BC (Eze-Uzomaka, 2009).

This production seems to have been in excess of local needs and therefore driven by trade with other peoples:

One aspect which can be inferred from the cylindrical slag blocks left behind is that the Lejja smelters must have had excess production of iron, and this may have led to extensive trade to far and distant places, sustained over a long period of time. (Eze-Uzomaka, 2009)

This metallurgy is unusual not only in its early date for West Africa but also in its subsequent development, which reached a high level of sophistication despite a lack of borrowing from metallurgical traditions in the Middle East and Europe. This may be seen in more than 700 artefacts of bronze, copper, and iron recovered from the Igbo-Ukwu site and dated to the 9th century AD:

They are the oldest bronze artifacts known in West African and were manufactured centuries before the emergence of other known bronze producing centers such as those of Ife and Benin. The bronzes include numerous ritual vessels, pendants, crowns, breastplates, staff ornaments, swords, and fly-whisk handles.

The Igbo-Ukwu bronzes amazed the world with a very high level of technical and artistic proficiency and sophistication which was at this time distinctly more advanced than bronze casting in Europe.

[...] Apparently the metal workers of ancient Igbo-Ukwu were not aware of commonly used techniques such as wire making, soldering or riveting which suggests an independent development and long isolation of their metal working tradition.

[...] Some of the techniques used by the ancient smiths are not known to have been used outside Igbo-Ukwu such as the production of complex objects in stages with the different parts later fixed together by brazing or by casting linking sections to join them. (Wikipedia, 2015) 

Contact with European traders

Thus, even before the first European contacts in the 16th century, the Igbo were already the focus of a network of trading relationships that extended outward from the Niger Delta. European traders became integrated into this trade network, thereby enabling the Igbo to emerge as valued middlemen in the slave trade: 

The peoples of south-eastern Nigeria have been involved in trade for as long as there are any records. The archaeological sites at Igbo-Ukwu and other evidence reveal long distance trade in metal and beads, as well as regional trade in salt, cloth, and beads at an early date. The lower Niger River and its Delta featured prominently in this early trade, and evidence is offered to suggest a continuity in the basic modes of trade on the lower Niger from c. A.D. 1500 to the mid-nineteenth century. An attempt to sketch the basic economic institutions of the Igbo hinterland before the height of the slave trade stresses regional trading networks in salt, cloth, and metal, the use of currencies, and a nexus of religious and economic institutions and persons. It is argued that while the growth of the slave trade appears to have been handled without major changes in the overall patterns of trade along the lower Niger, in the Igbo hinterland a new marketing 'grid', dominated by the Arochuku traders, was created using the pre-existent regional trading networks and religious values as a base. (Northrop, 1972)

British colonial rule

Great Britain took over Nigeria initially as part of its effort to outlaw the slave trade. Lagos was annexed in 1861 and a sphere of influence over the country was recognized in 1885 at the Berlin Conference, although a protectorate would not be proclaimed until 1901.

This new political environment favored the Igbo, whose initiative, self-discipline, and future orientation predisposed them to succeed not only in their homeland but also elsewhere in Nigeria, where they soon became dominant as merchants and civil servants. They thus took on a role like that of middleman minorities elsewhere in the empire, such as the Parsis in western India, the Chinese in Malaya, and the South Asians in East Africa. By the 1930s, one Igbo boasted that "the Ibo domination of Nigeria is a matter of time" (Ibrahim, 2000, p. 56). This trend even affected the army. By independence, 24 of the 52 senior army officers of the rank of major and above were Igbos (Ibrahim, 2000,p. 55).

This dominance led to jealousy among Nigerians in the north and west, who accused the Igbo of unfair business practices:

In the private sector they [the Hausa Muslims] are open to the exploitation of the Ibo control of the modern sector of private business activities. Ibos fix prices unilaterally by which Hausa money is siphoned daily. The Hausa are reduced to utter poverty and a large percentage of them rendered street beggars. (quoted in Ibrahim, 2000, p. 52)

According to Arthur Nwankwo (1985:9) "Nigerians of all other ethnic groups will probably achieve consensus on no other matter than their common resentment of the Igbo", a phenomenon that Chinua Achebe had dubbed "the Igbo problem". They argue that the Igbos are more cosmopolitan, more adapted to other cultures, more individualistic and competitive, more receptive to change and more prone to settle and work in other parts of the country but the myth persists that they are aggressive, arrogant and clannish. (Ibrahim, 2000, p.55)

Independence, civil war, and the aftermath

Independence came to Nigeria in 1960, and with it growing disillusionment among many Igbo, particularly with the perceived instability and corruption of the political process. In 1966, Igbo officers staged a coup and seized control of the country, killing the prime minister and the premiers of the northern and western regions. Northern army officers then staged a countercoup, and Igbo began to flee northern cities in the wake of persecution.

The next year, in 1967, the Igbo seceded and formed their own country, the Republic of Biafra. They lost the ensuing civil war at the cost of a million civilian deaths and a devastated homeland. Nonetheless, they are today building on "the remarkable Igbo economic and commercial élan that has occurred since the end of the civil war" (Ibrahim, 2000, p. 56).

Yet mistrust remains: "the North and the West have a deep-seated mistrust of the Igbo and so are bent on restricting, containing, and denying the Igbo their political right. Added to this is their subtle message to other minority groups: the Igbo, as a group, are not to be trusted!" (Abidde, 2004). This mistrust is founded on a not unjustified perception that the Igbo will prevail on any level playing field:

Collectively, the Igbo are wealthy, educated, and intelligent. These are people with global influence, strength of character, élan and self confidence. The Igbo nation has attributes most other Nigerian nations can only dream of; and are what most other nations are not. The Igbo made and makes Nigeria better. Any wonder then that the Igbo can do without Nigeria; but Nigeria and her myriad nationalities cannot do without the Igbo? Take the Igbo out of the Nigeria equation, and Nigeria will be a wobbling giant gasping for air! (Abidde, 2004)

Today, there is growing recognition in Nigeria that the Igbo can and should be given more political and economic power, but there is still a fear that they will use such power selfishly and not for the good of all Nigerians.

Conclusion

Chanda Chisala uses the Igbo example to refute the "hereditarian-HBD" argument. In doing so, he comes closer to the HBD position than he may realize. Recent work on gene-culture coevolution has shown that the average mental makeup of human populations can change significantly over a short span of historical time. This notably seems to have happened with the Ashkenazi Jews and the English between the Middle Ages and the 19th century (Clark et al., 2007; Cochran et al., 2006).

Why couldn't a similar process have happened with the Igbo? Why assume that sub-Saharan Africa is a monolith whose diverse populations have evolved in exactly the same way? We know that human genetic evolution didn't slow down with the coming of culture. It actually sped up (Hawks et al., 2007). For the most part, we humans have diversified genetically in response to differences in cultural environment and not to differences in natural environment. It is therefore plausible that the different cultures of Africa have had different effects on the gene pools of their respective populations.

I can hear the answer to my question: "You guys are the ones who think all blacks are alike!" Well, that isn't what I think.

On a final note, I couldn't help noticing the many commenters who complimented Chanda on sticking it to the HBD crowd. Don't they understand the logical contraposition? If it can be shown that some African groups have higher cognitive ability, doesn't the converse become plausible and even expectable?

Note

It may be that a similar sort of nickname had evolved into the word "Igbo" itself: "[...] some Ibo claim that the word "Hebrew" must have been mutilated to "Ubru" or "Ibru," then to "Uburu," and later to "Ibo."" (Butler, 1997, pp. 177-178). This is plausible, given that the Igbo initially had a weak sense of collective identity and may not have had a native name for themselves, thus inclining them to take a name given by outsiders. There are examples of this sort of thing elsewhere in Africa. The Tukulor of Senegal, for instance, were originally called the "two colors" by European travellers because some of them were light-skinned and others dark-skinned. 

References 

Abidde, S.O. (2004). The Nigerian Presidency and the Igbo Nation, Gamji
http://www.gamji.com/article3000/NEWS3755.htm 

Butler, J.S. (1997). Why Booker T. Washington was right. A reconsideration of the economics of race," in T.D. Boston (ed.) A Different Vision: African American economic thought, Volume 1, (pp. 174-193), Psychology Press
https://books.google.ca/books?id=WMwRwp9QImAC&printsec=frontcover&hl=fr&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false  
Chisala, C. (2015). The IQ gap is no longer a black and white issue, The Unz Review, June 25
http://www.unz.com/article/the-iq-gap-is-no-longer-a-black-and-white-issue/

Clark, G. (2007). A Farewell to Alms. A Brief Economic History of the World, Princeton University Press, Princeton and Oxford. 

Cochran, G., J. Hardy, and H. Harpending. (2006). Natural history of Ashkenazi intelligence, Journal of Biosocial Science, 38, 659-693.
http://harpending.humanevo.utah.edu/trial.link/Ashkenazi.pdf

Davison, C.C. (1972). Glass beads in African archaeology: Results of neutron activation analysis, supplemented by results of X-ray fluorescence analysis, Lawrence Berkeley Laboratory, University of California


Eze-Uzomaka, P. (2009). Iron and its influence on the prehistoric site of Lejja, World of Iron Conference
https://www.academia.edu/4103707/Iron_and_its_influence_on_the_prehistoric_site_of_Lejja 

Hawks, J., E.T. Wang, G.M. Cochran, H.C. Harpending, and R.K. Moyzis. (2007). Recent acceleration of human adaptive evolution, Proceedings of the National Academy of Sciences U.S.A., 104, 20753-20758.
http://www.researchgate.net/publication/5761823_Recent_acceleration_of_human_adaptive_evolution/file/9c9605240c4bb57b55.pdf 

Holl, A. F.C. (2009). Early West African Metallurgies: New Data and Old Orthodoxy, Journal of World Prehistory, 22, 415-438
http://www.researchgate.net/profile/Augustin_Holl/publication/226180393_Early_West_African_Metallurgies_New_Data_and_Old_Orthodoxy/links/00b7d52d503ee77a4c000000.pdf  
Ibrahim, J. (2000). The transformation of ethno-regional identities in Nigeria, in A. Jegga (ed.) Identity Transformation and Identity Politics Under Structural Adjustment in Nigeria, (pp. 41-61), Nordic Africa Institute.
https://books.google.ca/books?id=fUWLQv8-H70C&printsec=frontcover&hl=fr&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false 

Insoll, T. and T. Shaw. (1997). Gao and Igbo-Ukwu: Beads, interregional trade, and beyond, African Archaeological Review, 14, 9-23
http://link.springer.com/article/10.1007/BF02968364 

Northrup, D. (1972). The growth of trade among the Igbo before 1880, The Journal of African History, 13,217-236.
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=3234276&fileId=S0021853700011439

Sabino, R. and J. Hall. (1999). The path not taken: Cultural identity in the interesting life of Olaudah Equiano, MELUS, 24, 5-19. 

Wikipedia. (2015). Archaeology of Igbo-Ukwu
https://en.wikipedia.org/wiki/Archaeology_of_Igbo-Ukwu