April 30, 2010

The shape and tempo of language evolution (Greenhill et al. 2010)

This is an extremely interesting paper which addresses the claim that typological features of languages (e.g., whether they use Subject-Verb-Object) are more conservative than the lexicon. If that is the case, then typological features could be used to infer evolutionary relationships between languages that are older than ten thousand years or so (an upper limit on what can be inferred using vocabulary).

In general, the authors reject the idea of typological conservation, although they note that typological features differ in this respect, and some of them may appear to be conservative within some language family but evolve rapidly in another. Their tree reconstruction is able to infer well-known language families (e.g., Indo-European), or suspected ones (e.g., Nostratic), but the corresponding clusters are not robust (e.g., Hindi is broken away from the IE cluster, and unrelated non-Eurasian languages fall into the Nostratic one).

There is a freely available link to a preprint of the paper (pdf).

Proc Biol Sci. 2010 Apr 7. [Epub ahead of print]

The shape and tempo of language evolution.

Greenhill SJ, Atkinson QD, Meade A, Gray RD.


There are approximately 7000 languages spoken in the world today. This diversity reflects the legacy of thousands of years of cultural evolution. How far back we can trace this history depends largely on the rate at which the different components of language evolve. Rates of lexical evolution are widely thought to impose an upper limit of 6000-10 000 years on reliably identifying language relationships. In contrast, it has been argued that certain structural elements of language are much more stable. Just as biologists use highly conserved genes to uncover the deepest branches in the tree of life, highly stable linguistic features hold the promise of identifying deep relationships between the world's languages. Here, we present the first global network of languages based on this typological information. We evaluate the relative evolutionary rates of both typological and lexical features in the Austronesian and Indo-European language families. The first indications are that typological features evolve at similar rates to basic vocabulary but their evolution is substantially less tree-like. Our results suggest that, while rates of vocabulary change are correlated between the two language families, the rates of evolution of typological features and structural subtypes show no consistent relationship across families.


Broad-faced men and trustworthiness

Related: Broad-faced men are more aggressive

Psychol Sci. 2010 Mar 1;21(3):349-54. Epub 2010 Feb 16.

Valid facial cues to cooperation and trust: male facial width and trustworthiness.

Stirrat M, Perrett DI.


Decisions about whom to trust are biased by stable facial traits such as attractiveness, similarity to kin, and perceived trustworthiness. Research addressing the validity of facial trustworthiness or its basis in facial features is scarce, and the results have been inconsistent. We measured male trustworthiness operationally in trust games in which participants had options to collaborate for mutual financial gain or to exploit for greater personal gain. We also measured facial (bizygomatic) width (scaled for face height) because this is a sexually dimorphic, testosterone-linked trait predictive of male aggression. We found that men with greater facial width were more likely to exploit the trust of others and that other players were less likely to trust male counterparts with wide rather than narrow faces (independent of their attractiveness). Moreover, manipulating this facial-width ratio with computer graphics controlled attributions of trustworthiness, particularly for subordinate female evaluators.


April 29, 2010

A cautionary tale for wheat domestication

What this paper shows is that an ancestral allele believed to have been lost during wheat domestication, was actually present in 19th century wheat cultivars. What this means is that (a) the derived allele may not be fixed (100% frequency) but may co-exist with the ancestral one, and (b) if it is indeed fixed, then this fixation did not occur in Neolithic times, but over the last century and a half or so.

Journal of Archaeological Science doi:10.1016/j.jas.2010.04.003

Re-evaluating the history of the wheat domestication gene NAM-B1 using historical plant material

Linnéa Asplund et al.


The development of agriculture is closely associated with the domestication of wheat, one of the earliest crop species. During domestication key genes underlying traits important to Neolithic agriculture were targeted by selection. One gene believed to be such a domestication gene is NAM-B1, affecting both nutritional quality and yield but with opposite effects. A null mutation, first arisen in emmer wheat, decreases the nutritional quality but delays maturity and increases grain size; previously the ancestral allele was believed lost during the domestication of durum and bread wheat by indirect selection for larger grain. By genotyping 63 historical seed samples originating from the 1862 International Exhibition in London, we found that the ancestral allele was present in two spelt wheat and two bread wheat cultivars widely cultivated at the time. This suggests that fixation of the mutated allele of NAM-B1 in bread wheat, if at all, occurred during modern crop improvement rather than during domestication. We also discuss the value of using archaeological and historical plant material to further the understanding of the development of agriculture.


April 27, 2010

Y chromosomes of Northwest China

I am not very surprised with the presence of J2 in Northwest China, as it was previously detected among Uyghurs of the region. My guess is that J2 was a major component of the eastward migrations of Indo-Iranians (in this case Iranic-speaking Sakas probably) and was later absorbed by the westward-moving Altaic groups that swept through the Eurasian heartland.

We urgently need ancient DNA to bridge the gap between the earliest Caucasoids to arrive at China (which included R1a1, but sample sizes are really too small to exclude the presence of other haplogroups), and the present-day populations where other lineages of West Eurasian origin are present.

J Hum Genet doi:10.1038/jhg.2010.30.

Y-chromosome distributions among populations in Northwest China identify significant contribution from Central Asian pastoralists and lesser influence of western Eurasians

Shou WH et al.


Northwest China is closely adjacent to Central Asia, an intermediate region of the Eurasian continent. Moreover, the Silk Road through the northwest of China once had a vital role in the east-west intercommunications. Nevertheless, little has been known about the genetic makeup of populations in this region. We collected 503 male samples from 14 ethnic groups in the northwest of China, and surveyed 29 Y-chromosomal biallelic markers and 8 short tandem repeats (STRs) loci to reconstruct the paternal architecture. Our results illustrated obvious genetic difference among these ethnic groups, and in general their genetic background is more similar with Central Asians than with East Asians. The ancestors of present northwestern populations were the admixture of early East Asians peopling northwestward and later Central Asians immigrating eastward. This population mixture was dated to occur within the past 10 000 years. The J2-M172 lineages likely entered China during the eastward migration of Central Asians. The influence from West Eurasia through gene flows on the extant ethnic groups in Northwest China was relatively weak.


Empathy for one's own race neurally distinct from empathy from mankind

From the related public release:
In a rare neuroscience look at racial minorities, the study shows that African-Americans showed greater empathy for African-Americans facing adversity – in this case for victims of Hurricane Katrina – than Caucasians demonstrated for Caucasian-Americans in pain.

"We found that everybody reported empathy toward the Hurricane Katrina victims," said Joan Y. Chiao, assistant professor of psychology and author of the study. "But African-Americans additionally showed greater empathic response to other African-Americans in emotional pain."

The more African-Americans identified as African-American the more likely they were to show greater empathic preference for African-Americans, the study showed.

NeuroImage doi:10.1016/j.neuroimage.2010.03.025

Neural basis of extraordinary empathy and altruistic motivation

Vani A. Mathur et al.


A central evolutionary challenge for social groups is uniting a heterogeneous set of individuals towards common goals. One means by which social groups form and endure is by endowing group members with extraordinary prosocial proclivities, such as ingroup love, towards other group members. Here we examined the neural basis of extraordinary empathy and altruistic motivation in African-American and Caucasian-American individuals using functional magnetic resonance imaging. Our results indicate that empathy for ingroup members is neurally distinct from empathy for humankind, more generally. People showed greater response within anterior cingulate cortex and bilateral insula when observing the suffering of others, but African-American individuals additionally recruit medial prefrontal cortex when observing the suffering of members of their own social group. Moreover, neural activity within medial prefrontal cortex in response to pain expressed by ingroup relative to outgroup members predicted greater empathy and altruistic motivation for one's ingroup, suggesting that neurocognitive processes associated with self identity underlie extraordinary empathy and altruistic motivation for members of one's own social group. Taken together, our findings reveal distinct neural mechanisms of empathy and altruistic motivation in an intergroup context and may serve as a foundation for future research investigating the neural bases of intergroup prosociality, more broadly construed.


Human brain recognizes race

From the public release:
Typically, when people observe others perform a simple task, their motor cortex region fires similarly to when they are performing the task themselves. However, the UofT research team, led by PhD student Jennifer Gutsell and Assistant Professor Dr. Michael Inzlicht, found that participants' motor cortex was significantly less likely to fire when they watched the visible minority men perform the simple task. In some cases when participants watched the non-white men performing the task, their brains actually registered as little activity as when they watched a blank screen.
From the paper:
A deficit in the spontaneous ‘‘catching” of outgroup members’ actions and intentions can have serious consequences for intergroup interactions. Perception–action-coupling, and the sharing of somatic, autonomic, and emotional states, facilitate social understanding and foster helping, morality, altruism, and justice
(Batson et al., 1997; Cialdini, Brown, Lewis, Luce, & Neuberg, 1997). Thus, people might not be as responsive to outgroup member’s needs and feelings and be less likely to understand their intentions; they might also be less likely to help and effectively communicate with them.
This sounds like a good example of what I called friction in a recent post.

Also from the paper:
When we breakdown the omnibus outgroup correlation into the specific racial outgroups, we find results that are consistent with a Canadian context: the correlation was strongest for South-Asians, r (28) = .56, p less than .01, and followed by Blacks, r (28) = .36, p = .05; the correlation for East Asians, however, fell below traditional levels of significance, r (28) = .30, p = .11. Since mu activity is inversely related to motor cortex activity, these findings suggest that the more participants are prejudiced, the less their motor cortex fires in response to the passive viewing of outgroup members’ actions—an effect that is magnified for disliked outgroups (South-Asians, then Blacks, followed by East Asians).
The order of the outgroups suggests that genetic-phenotypic similarity is not the end-all, as South Asians are closer to whites but perhaps less familiar to them, due to a shorter period of their presence in Western societies.

Journal of Experimental Social Psychology doi:10.1016/j.jesp.2010.03.011

Empathy constrained: Prejudice predicts reduced mental simulation of actions during observation of outgroups

Jennifer N. Gutsell, and Michael Inzlicht


Perception–action-coupling refers to the vicarious activation of the neural system for action during perception of action, and is considered important for forms of interpersonal sensitivity, including empathy. We hypothesize that perception–action-coupling is limited to the ingroup: neural motor networks will fire upon the perception of action, but only when the object–person belongs to the ingroup; if the object–person belongs to an outgroup these motor neurons will not fire. Using electroencephalographic oscillations as an index of perception–action-coupling, we found exactly this: participants displayed activity over motor cortex when acting and when observing ingroups act, but not when observing outgroups – an effect magnified by prejudice and for disliked groups (South-Asians, then Blacks, followed by East Asians). These findings provide evidence from brain activity for yet another detrimental aspect of prejudice: a spontaneous and implicit simulation of others’ action states may be limited to close others and, without active effort, may not be available for outgroups.


April 24, 2010

Α Historical and Demographic Model of Recent Human Evolution (Laval et al. 2010)

The authors interpret their data in the following way: Out of Africa ~60,000 years ago, then a long period of Eurasian unity, followed by separation of Europeans from East Asians ~22,500 years ago.

As I have argued before, this makes very little sense. Why would a mobile species that is beginning to populate the world form a unity until so late. Indeed, we have arrival of modern humans in both Europe and East Asia long before the ~22.5kya date, and the divergence of these humans into the two major Eurasian races starts already in the Paleolithic. The idea that the ancestors of modern Caucasoids and Mongoloids formed a unity as late as ~22.5kya is a fantasy.

What gives then? The problem arises from the failure to appreciate intra-African variation. The temporal gap between the demographic expansion of Homo sapiens and Eurasians is not due to an early Out of Africa event followed by a period of stasis.

Rather, the Out-of-Africa event was one side of a coin that included a related Deeper-into-Africa event. The fourty thousand year gap is, in part, due to population structure in Africa itself, with Eurasians being late descendants of an East African subpopulation and modern Africans being an admixture of East Africans and the pre-existing populations of the continent, whose least admixed modern representatives are the Khoi-San and Pygmies.

It makes no sense that Eurasians left Africa and then "stayed as one" for forty thousand years, just as they had the Earth's largest landmass to populate and the record says that they did populate it. Rather, the forty thousand year gap should be split into "African" and "Eurasian" components, with the former representing African population structure that later broke down, forming the present-day mosaic of African peoples, and the latter representing the early period of Eurasian unity during the early stages of our species' Out of Africa adventures.

It is telling that the authors consider a model in which the ancestors of modern humans replaced archaic humans in Eurasians, but it does not dawn on them at all, that these same ancestors may have replaced or absorbed archaic humans (or early modern ones) in Africa itself.

PLoS ONE doi: 10.1371/journal.pone.0010284

Formulating a Historical and Demographic Model of Recent Human Evolution Based on Resequencing Data from Noncoding Regions

Guillaume Laval et al.


Estimating the historical and demographic parameters that characterize modern human populations is a fundamental part of reconstructing the recent history of our species. In addition, the development of a model of human evolution that can best explain neutral genetic diversity is required to identify confidently regions of the human genome that have been targeted by natural selection.

Methodology/Principal Findings
We have resequenced 20 independent noncoding autosomal regions dispersed throughout the genome in 213 individuals from different continental populations, corresponding to a total of ~6 Mb of diploid resequencing data. We used these data to explore and co-estimate an extensive range of historical and demographic parameters with a statistical framework that combines the evaluation of multiple models of human evolution via a best-fit approach, followed by an Approximate Bayesian Computation (ABC) analysis. From a methodological standpoint, evaluating the accuracy of the parameter co-estimation allowed us to identify the most accurate set of statistics to be used for the estimation of each of the different historical and demographic parameters characterizing recent human evolution.

Our results support a model in which modern humans left Africa through a single major dispersal event occurring ~60,000 years ago, corresponding to a drastic reduction of ~5 times the effective population size of the ancestral African population of ~13,800 individuals. Subsequently, the ancestors of modern Europeans and East Asians diverged much later, ~22,500 years ago, from the population of ancestral migrants. This late diversification of Eurasians after the African exodus points to the occurrence of a long maturation phase in which the ancestral Eurasian population was not yet diversified.


April 22, 2010

Origin and dispersal of mtDNA haplogroup U5 (Malyarchuck et al. 2010)

From the conclusion:
Genetic data obtained in this study allows the suggestion that during the LGM period, central European territories probably represented the area of intermingling between human flow from refugial zones in the Balkans, the Mediterranean coastline and the Pyrenees, as U5a and U5b gene flows occurred from there. Based on dating analysis of the U5 subclusters, it seems very likely that, despite the archaeological evidence testifying to the presence of humans in eastern Europe during the Ice Age, this part of Eurasia might have only been re-populated by modern humans at the end of the LGM, i.e. later than central Europe. In addition, U5b gene flow from central to eastern Europe become much more intense after the LGM. In general, we believe that molecular genetic data, in addition to archaeological and fossil evidence, are of significant use for resolving key questions regarding the interaction of human communities and climate.
The presence of mtDNA U2 in Russia (Kostenki) 30 thousand years ago, and the discovery of plentiful U5 in pre-farming populations is consistent with the scenario proposed by the authors. Now, if we find a U5 type in eastern Europe of e.g., Kostenki-age, the authors' hypothesis will be rejected. But, so far, the late (but pre-farming) time frame proposed by the authors is consistent with all our ancient European mtDNA sample points.

The sequence of events, as they now appear, include the earliest appearance of U2 in the eastern European plain (and possibly U4), the later appearance of U5, and then the advent of farming via the Balkans and Central Europe which brought the full suite of present-day Caucasoid haplogroups into the region.

PLoS ONE doi:10.1371/journal.pone.0010285

The Peopling of Europe from the Mitochondrial Haplogroup U5 Perspective

Boris Malyarchuk et al.


It is generally accepted that the most ancient European mitochondrial haplogroup, U5, has evolved essentially in Europe. To resolve the phylogeny of this haplogroup, we completely sequenced 113 mitochondrial genomes (79 U5a and 34 U5b) of central and eastern Europeans (Czechs, Slovaks, Poles, Russians and Belorussians), and reconstructed a detailed phylogenetic tree, that incorporates previously published data. Molecular dating suggests that the coalescence time estimate for the U5 is ~25–30 thousand years (ky), and ~16–20 and ~20–24 ky for its subhaplogroups U5a and U5b, respectively. Phylogeographic analysis reveals that expansions of U5 subclusters started earlier in central and southern Europe, than in eastern Europe. In addition, during the Last Glacial Maximum central Europe (probably, the Carpathian Basin) apparently represented the area of intermingling between human flows from refugial zones in the Balkans, the Mediterranean coastline and the Pyrenees. Age estimations amounting for many U5 subclusters in eastern Europeans to ~15 ky ago and less are consistent with the view that during the Ice Age eastern Europe was an inhospitable place for modern humans.


Y chromosome variation in NW New Guinea

A 2007 paper that slipped through my net at the time it appeared, but is interesting to read as it was cited in the recent study by Cox et al. (2010)

Molecular Biology and Evolution 2007 24(11):2546-2555; doi:10.1093/molbev/msm187

Patterns of Y-Chromosome Diversity Intersect with the Trans-New Guinea Hypothesis

Stefano Mona et al.


The island of New Guinea received part of the first human expansion out of Africa (>40,000 years ago), but its human genetic history remains poorly understood. In this study, we examined Y-chromosome diversity in 162 samples from the Bird's Head region of northwest New Guinea (NWNG) and compared the results with previously obtained data from other parts of the island. NWNG harbors a high level of cultural and linguistic diversity and is inhabited by non-Austronesian (i.e., Papuan)–speaking groups as well as harboring most of West New Guinea's (WNG) Austronesian-speaking groups. However, 97.5% of its Y-chromosomes belong to 5 haplogroups that originated in Melanesia; hence, the Y-chromosome diversity of NWNG (and, according to available data, of New Guinea as a whole) essentially reflects a local history. The remaining 2.5% belong to 2 haplogroups (O-M119 and O-M122) of East Asian origin, which were brought to New Guinea by Austronesian-speaking migrants around 3,500 years ago. Thus, the Austronesian expansion had only a small impact on shaping Y-chromosome diversity in NWNG, although the linguistic impact of this expansion to this region was much higher. In contrast, the expansion of Trans-New Guinea (TNG) speakers (non-Austronesian) starting about 6,000–10,000 years ago from the central highlands of what is now Papua New Guinea, presumably in combination with the expansion of agriculture, played a more important role in determining the Y-chromosome diversity of New Guinea. In particular, we identified 2 haplogroups (M-P34 and K-M254) as suggestive markers for the TNG expansion, whereas 2 other haplogroups (C-M38 and K-M9) most likely reflect the earlier local Y-chromosome diversity. We propose that sex-biased differences in the social structure and cultural heritage of the people involved in the Austronesian and the TNG expansions played an important role (among other factors) in shaping the New Guinean Y-chromosome landscape.


April 21, 2010

More on geographical divide between Asian and Melanesian types in Indonesia (Cox et al. 2010)

I had previously posted about a paper showing a sharp divide in Indonesia between "Asian" and "Melanesian" Y chromosomes. A reader alerts me to another paper from this year, which discovers this divide using autosomal and X chromosome polymorphisms.

From the paper:
this transition is shifted eastward relative to Wallace’s line—a boundary that separates the biogeographic regions of Asia and Wallacea. At its southern limit, Wallace’s line falls between the islands of Bali and Lombok (figure 1), which are separated by a deep-water sea channel that marks the southern edge of the Sunda
Shelf. During ice-age glacial advances, the Sunda land mass included Borneo, Bali, Java and Sumatra, together with mainland Southeast Asia. However, even in periods
of low sea level, deep water in Wallacea separated the Sunda shelf from the eastern landmass of Sahul (connecting New Guinea and Australia). While the distribution of
many flora and fauna conforms to Wallace’s line, the seafaring capabilities of human settlers to this region undoubtedly overcame this barrier to dispersal. Indeed, Asian ancestry exceeds 50 per cent as far east as the island of Alor, which is well within Wallacea and approximately 1000 km east of Bali, as well as on the island of Sulawesi, which is located east of Wallace’s line in the north (figure 1). Curiously, Wallace himself noted this difference, positing a second line in eastern Indonesia corresponding to changes in human phenotype (Wallace 1869; Cox 2008). Wallace’s second ‘phenotypic’ line broadly parallels the rapid decline in Asian admixture identified here. It is refreshing to see (for once) a paper which acknowledges that modern genetics did not discover the wheel but has to a large extent confirmed what previous generations of scientists, working with their eyes (and later their calipers) could plainly see.
A visually interesting figure from the paper illustrates what a "cline" actually is.

We can see how west of 120 degrees longitude there is a uniform area of Asian ancestry, then a sharp transition zone and then a fairly uniform area of Melanesian ancestry.

The above figure illustrates one of the arguments of those (like me) who assert that racial variation in humans is real: the fact that it geographically punctuated (no smooth cline). The smooth areas of uniformity east/west of 120deg deserve to be recognized as real entities.

For visual illustration, three examples from Deniker's The races of man: a New Caledonian woman representing an "eastern" Melanesian type, a group of people from Flores (where, according to the current paper Asian admixture runs at 62%), and finally a Javan man representing a "western" Indonesian Mongoloid type.

Proc. R. Soc. B (2010) 277, 1589–1596

Autosomal and X-linked single nucleotide polymorphisms reveal a steep Asian–Melanesian ancestry cline in eastern Indonesia and a sex bias in admixture rates

Murray P. Cox


The geographical region between mainland Asia and New Guinea is characterized by numerous small islands with isolated human populations. Phenotypically, groups in the west are similar to their neighbours in mainland Southeast Asia, eastern groups near New Guinea are similar to Melanesians, and intervening populations are intermediate in appearance. A long-standing question is whether this pattern primarily reflects mixing between groups with distinct origins or whether natural selection has shaped this range of variation by acting differentially on populations across the region. To address this question, we genotyped a set of 37 single nucleotide polymorphisms that are evolutionarily independent, putatively neutral and highly informative for Asian–Melanesian ancestry in 1430 individuals from 60 populations spanning mainland Asia to Melanesia. Admixture analysis reveals a sharp transition from Asian to Melanesian genetic variants over a narrow geographical region in eastern Indonesia. Interestingly, this admixture cline roughly corresponds to the human phenotypic boundary noted by Alfred Russell Wallace in 1869. We conclude that this phenotypic gradient probably reflects mixing of two long-separated ancestral source populations—one descended from the initial Melanesian-like inhabitants of the region, and the other related to Asian groups that immigrated during the Paleolithic and/or with the spread of agriculture. A higher frequency of Asian X-linked markers relative to autosomal markers throughout the transition zone suggests that the admixture process was sex-biased, either favouring a westward expansion of patrilocal Melanesian groups or an eastward expansion of matrilocal Asian immigrants. The matrilocal marriage practices that dominated early Austronesian societies may be one factor contributing to this observed sex bias in admixture rates.


April 19, 2010

Are mixed-race people more attractive?

This paper has received some attention in the media, so it is worthwhile to consider its thesis: that great attractiveness of mixed-race people is due to genetic heterosis.

From the paper:
Facial images were harvested from the social networking website facebook.com. These were collected according to social groups that the people submitting the images belonged to. People who were members of groups making reference to being of mixed race [eg ``mixed race and proud of it''](1) formed a mixed-race group (N . 483). People who were members of groups making reference to groups who were from geographical regions of the UK with minimal ethnic minorities (eg ``Cornish and proud of it'') formed a white group (N . 368). People who were members of groups that made reference to being Black and living in the UK (eg ``Black and brum'') or made reference to coming from parts of Africa (eg ``Gambian and proud'') formed a black group (N . 354).


Twenty white psychology students rated each face on its attractiveness on a 9-point scale (5 being of average attractiveness).
Before we consider the "Why" of the paper's title, it is worthwhile to consider whether the thesis itself "mixed-race people are perceived as more attractive" is supported by the evidence. I can think of several alternative explanations for the evidence:
  • There is no reason to think that "mixed-race" people represent black-white mixes. In the British context, "mixed-race" may also include white-South Asian or white-East Asian people.
  • There is no reason to think that white people from less cosmopolitan areas are equally attractive to white people from big cities. It's reasonable to assume that attractive people thrive in regions of high population density, since attractiveness is a social advantage: you will probably find more "hot" models, actors, PR people, waitresses, salesgirls, etc. in London than you will in Cornwall.
  • There is no reason to think that people of average attractiveness (for their respective races) mate to produce mixed-race offspring. Interracial marriage is not the norm (it occurs at a far lower rating than random mating would predict), thus there appears to be a real psychological impediment to the practice. It is not unreasonable to postulate that people are willing to mate interracially for a higher-than-average member of a different race, with the greater attractiveness serving to overcome this obstacle. In any case, the assumption that random whites and blacks mate to produce interracial offspring is not obvious.
  • There is no reason to think that people who join mixed-race groups on facebook are good representatives of mixed-race people in general. Non-normative individuals may have a positive, neutral, or negative attitude towards their ancestry, and it is reasonable that "happy" mixed-race people may be more likely to advertise the fact than "non-happy" ones, and that more attractive mixed-race people (representing more harmonious combinations) may be more likely to belong to the first category.
  • Finally, there is no reason to think that people who are of mixed-race have the same age as non-mixed people. Race mixing is on the rise both due to immigration and to changing societal norms, so there is probably a negative correlation between racial admixture and age. Thus, the finding of this study may be simply an artifact of the higher average age of the unmixed vs. the mixed groups.
Thus, I don't really think there is any reason to seek the "why" of a non-evident fact. But, it is interesting to consider the explanation for the supposed greater attractiveness of mixed-race people: genetic heterosis. The paper really offers no new evidence that heterosis has an effect on attractiveness.

It would be worthwhile to do a comprehensive study of race and attractiveness. Thankfully, we now possess reasonable genetic estimators of racial admixture and heterozygosity; hopefully someone will have the funds and will to use them.

Nonetheless the paper is useful because it reveals a real effect: what the explanation for this effect is remains to be seen.

Perception 39(1) 136 – 138

Why are mixed-race people perceived as more attractive?

Michael B Lewis


Previous, small scale, studies have suggested that people of mixed race are perceived as being more attractive than non-mixed-race people. Here, it is suggested that the reason for this is the genetic process of heterosis or hybrid vigour (ie cross-bred offspring have greater genetic fitness than pure-bred offspring). A random sample of 1205 black, white, and mixed-race faces was collected. These faces were then rated for their perceived attractiveness. There was a small but highly significant effect, with mixed-race faces, on average, being perceived as more attractive. This result is seen as a perceptual demonstration of heterosis in humans—a biological process that may have implications far beyond just attractiveness.


April 15, 2010

"Aunty": 600-year old Maori woman reconstructed

Iwi face to face with "Aunty"
The face of a Maori woman who died on the Wairau bar in Marlborough more than 600 years ago has been revealed using digital technology.

Skulls found on the Wairau Bar in 1939 have been used to help digitally recreate the faces of the people who once lived there.

Local iwi Rangitane have affectionately renamed the woman as "aunty".

Video from above story.

Maori ancestor face mapped
It's not easy to visualise what our ancestors might have looked like, but now digital technology has allowed a group of researchers to reconstruct the face of a Maori woman using her 600 year old skull.

The woman the local iwi Rangitane have come to call "Aunty" lived in New Zealand's Marlborough region. Her skull was recovered several decades ago, but it's taken until now to repatriate the remains and reconstruct her face.

Audio from above story.

April 14, 2010

Origin of South African Couloured population

Photo from Wikipedia article.

AJHG doi:10.1016/j.ajhg.2010.02.014

Strong Maternal Khoisan Contribution to the South African Coloured Population: A Case of Gender-Biased Admixture

Lluis Quintana-Murci et al.


The study of recently admixed populations provides unique tools for understanding recent population dynamics, socio-cultural factors associated with the founding of emerging populations, and the genetic basis of disease by means of admixture mapping. Historical records and recent autosomal data indicate that the South African Coloured population forms a unique highly admixed population, resulting from the encounter of different peoples from Africa, Europe, and Asia. However, little is known about the mode by which this admixed population was recently founded. Here we show, through detailed phylogeographic analyses of mitochondrial DNA and Y-chromosome variation in a large sample of South African Coloured individuals, that this population derives from at least five different parental populations (Khoisan, Bantus, Europeans, Indians, and Southeast Asians), who have differently contributed to the foundation of the South African Coloured. In addition, our analyses reveal extraordinarily unbalanced gender-specific contributions of the various population genetic components, the most striking being the massive maternal contribution of Khoisan peoples (more than 60%) and the almost negligible maternal contribution of Europeans with respect to their paternal counterparts. The overall picture of gender-biased admixture depicted in this study indicates that the modern South African Coloured population results mainly from the early encounter of European and African males with autochthonous Khoisan females of the Cape of Good Hope around 350 years ago.


April 13, 2010

Children with Williams syndrome lack racial stereotyping

Info on What is Williams syndrome.

Current Biology, Volume 20, Issue 7, R307-R308, 13 April 2010, doi:10.1016/j.cub.2010.02.009

Absence of racial, but not gender, stereotyping in Williams syndrome children

Andreia Santos et al.


Stereotypes — often implicit attributions to an individual based on group membership categories such as race, religion, age, gender, or nationality — are ubiquitous in human interactions. Even three-year old children clearly prefer their own ethnic group and discriminate against individuals of different ethnicities [1]. While stereotypes may enable rapid behavioural decisions with incomplete information, such biases can lead to conflicts and discrimination, especially because stereotypes can be implicit and automatic [2], making an understanding of the origin of stereotypes an important scientific and socio-political topic. An important process invoked by out-groups is social fear [3]. A unique opportunity to study the contribution of this mechanism to stereotypes is afforded by individuals with the microdeletion disorder Williams syndrome (WS), in which social fear is absent, leading to an unusually friendly, high approachability behaviour, including towards strangers [4]. Here we show that children with WS lack racial stereotyping, though they retain gender stereotyping, compared to matched typically developing children. Our data indicate that mechanisms for the emergence of gender versus racial bias are neurogenetically dissociable. Specifically, because WS is associated with reduced social fear, our data support a role of social fear processing in the emergence of racial, but not gender, stereotyping.


April 11, 2010

Face of 11-year-old victim of the Great Plague of Athens

On the top left you can see a forensic reconstruction of an 11-year old girl (nicknamed "Myrtis") who died during the Great Plague in 5th c. BC Athens. You can probably get a basic understanding of the Greek article in Ta Nea, via Google Translate.

April 10, 2010

Hard problems in Social Science symposium: a couple of my propositions

The Hard Problems in Social Science symposium is happening today, and there is a live webcast of the event. From the symposium announcement:
During the daylong symposium, a panel of experts from multiple universities will individually present what they believe to be the hardest unsolved problems in the social sciences, emphasizing both why the problems are hard and why they are important. At the end of the day the panelists will debate their proposals with each other and with the audience. Over the days and months following the event, anyone from around the world will be able to view streaming video of the symposium, vote on the proposed problems, and, perhaps most important, submit additional problems for consideration and voting.

The final votes will be used, in combination with the symposium proceedings, to develop a prioritized list that we hope will serve to focus and inform research and policy directions, as well as funding support, in the future.
I don't quite think that there are hard problems in the social sciences in the sense of Hilbert's original 1900 problems. The reason for this is simple: we know when one of Hilbert's problems has been solved, but it's hard, or even impossible to know when a social science problem has been answered to everyone's satisfaction. To quote Aristotle's Nicomachean ethics:
Our discussion will be adequate if it has as much clearness as the subject-matter admits of, for precision is not to be sought for alike in all discussions, any more than in all the products of the crafts. Now fine and just actions, which political science investigates, admit of much variety and fluctuation of opinion, so that they may be thought to exist only by convention, and not by nature. And goods also give rise to a similar fluctuation because they bring harm to many people; for before now men have been undone by reason of their wealth, and others by reason of their courage. We must be content, then, in speaking of such subjects and with such premisses to indicate the truth roughly and in outline, and in speaking about things which are only for the most part true and with premisses of the same kind to reach conclusions that are no better. In the same spirit, therefore, should each type of statement be received; for it is the mark of an educated man to look for precision in each class of things just so far as the nature of the subject admits; it is evidently equally foolish to accept probable reasoning from a mathematician and to demand from a rhetorician scientific proofs.

With the caveat that social science hard problems are not "hard" and cannot be solved in the same way as those of mathematics, here is what I think are two of the hardest problems in the social sciences.

Homogeneity vs. Diversity

Paying lip service to diversity is a favorite pastime in the western world. Indeed, (genetic or cultural) diversity has its advantages. From the genetic standpoint, increased genetic diversity increases the chances that the population will be able to adapt to changes in its environment. A race of clones is doomed to extinction if its genetic Achilles' heel is discovered; that is less likely for a diverse population where there is enough variability to ensure adequate response to selection pressure.

From the cultural standpoint, diversity can also be an asset. It is pleasant to have different choices of food, dress, entertainment, or to be able to talk to people with different backgrounds and life experiences. It is sometimes also practical: having people with different perspectives is a good way to ensure intellectual alertness as cultures tend to stagnate in their own assumptions if they are not continually challenged by people with a fresh viewpoint (whether these are young ones who have not yet internalized their society's tradition, or foreigners who view it as something novel).

However, the downsides of diversity are also numerous. Two are particularly important, and I will call them friction and hierarchy.

By "friction", I refer to the ineffectiveness of diversity. While having 10 different languages may make the expression of cultural nuances possible, it makes communication more difficult as these nuances are "lost in translation". Indeed, friction may reach explosive levels, both because heterogeneity breeds distrust, or even outright conflict as different segments of society begin to see themselves as inimical to each other.

By "hierarchy", I refer to the fact that some things that are unequal may in fact be organized in terms of superiority or inferiority. Different foods may all be pleasant to have as options, but they are not all equally good for one's health. Sickle-cell trait may harden the population against outbreaks of malaria, but it is not exactly pleasant at the level of individual. Monogamy or polygamy may be different social practices, but they have important adverse consequences for societal functioning (e.g., cheating by polygynous-inclined males in monogamous societies vs. an excess of unattached, potentially troublesome, males in polygynous ones).

To conclude: it is time to go beyond the "diversity is power" slogans and study the problem of homogeneity vs. diversity with an open mind, trying to figure out when, how, and what kind of diversity is good.

Central control vs. Open Society

The argument for central control was put succinctly by the Platonic Socrates who made the argument that when a ship is in danger the captain has command, and not the assembly of sailors, because the captain has superior knowledge of what is to be done.

The argument for "open society" and its more libertarian or even anarchic versions is that the leader --any leader-- is prone to error or misuse of power, so it is better to organize society bottom-up, and to trust in peoples' ability to find good solutions to their problems.

Psychologically most 21st century people feel a revulsion against the idea of their lives ruled by unelected philosopher kings. On the other hand, there is an abundance of examples of democracies shooting themselves in the foot, and the idea that a captain should lead the sailors is intuitively right.

Indeed, we accept central control in a number of different social institutions, e.g., sports teams, corporations, classrooms, or military units. Coaches, CEOs, teachers, or COs lead these organizations, and the principle of democracy goes out the window.

If there was an optimal decision maker, then most people would be fine with ceding control to them. That is why some historical rulers are known as either heroes or tyrants. Those who make good decisions and keep their societies strong and happy are elevated while those who bring them to ruin are demonized.

An unstated assumption in political science is that different constitutions can be evaluated in isolation, without considering the actual states and populaces over which they will be instituted.

Democracy, we are told, is best, but how good is it really in a society filled with superstition and lacking in scientific knowledge? How can we expect such a society to democratically decide what is good for it? Or, how appropriate is democracy in a society of abundance where decisions can be made rationally and cool-headedly, vs. a dog-eat-dog society of scarcity where voting majorities may be inclined to live at the expense of minorities?

The modern world as a whole experiences an increase in expertise. Moreover, problems are increasingly technical in nature: the average citizen doesn't have a clue about how serious climate change is, or how drastic measures to address it should be enforced.

To summarize: putting down democracy is unpopular, but it is time to see how it can function in today's world, as opposed to the small-scale states it was first instituted in. The goal: to figure out which problems should be decided democratically and which should be left to experts, and to create a political system that will distinguish between the two.

April 09, 2010

Y-chromosome polymorphisms in Russia (Bellusci et al. 2010)

This is a very important paper which samples Y chromosome variation in Russia (including ethnic Russians and other populations) and neighboring countries.

On the left, the MDS plot showing relationships of the populations included in the study.

Unfortunately the samples were not Y-SNP typed, but the testing of 16 Y-STR markers is more than usual for a scientific study and should be more than enough for those interested in inferring the haplogroup composition of the studied populations.

Of interesting is the following observation from the paper:
In particular the Rst’s within groups were 0.093, 0.0, 0.070 and 0.156 for Uralic, Kartevelian, Indo-European and Altaic, respectively, confirming the latter as the most heterogeneous language family among those represented here.
I mention this because it shows how easily it is to be misled by genetic diversity measures into erroneous conclusions about the antiquity of populations and their dispersals, a point I have often made before. Altaic is the youngest language to have dispersed in the territory in question, but its speakers are the most genetically heterogeneous.

On the other hand, Kartvelian is probably fairly young, and its speakers are fairly homogeneous, but there can be little doubt that it is a young offshoot of a very ancient linguistic branch that has survived in the Caucasus and was unaffected by the Indo-Europeanization and Altaicization of neighboring populations.

Note also how geographical range restrictions affect estimates of genetic heterogeneity within language families. For example, Indo-European here is represented largely by Slavs; if other IE-speakers were represented, genetic heterogeneity within that group would be increased. Indeed, just as Kartvelian represents a young offshoot within the South Caucasian language family, so does Slavic represent a young offshoot within the Indo-European one.

The situation is not too dissimilar to that in Southwestern Europe where another young IE offshoot (Romance) has replaced pre-existing Indo-European (Italo-Celtic) variation.

Older posts on the same topic:
Annals of Human Biology

The landscape of Y chromosome polymorphisms in Russia

Giovanna Bellusci et al.


Background: The pattern of diversity for the Y chromosome provides a view of male-driven processes of dispersal and settlement. By virtue of the broad geographic continuity, the genetic signature of movements from Asia to Europe can be detected in populations of north-eastern Europe.

Aim: To directly test previous hypotheses on the peopling of Russia, by considering a broader spectrum of potential diversity.

Subjects and methods: A total of 636 unrelated males (24 samples) from geographically and ethnically defined populations of Russia, Belarus, Azerbaijan and Georgia were analysed for 16 Y-STR loci. Some of the populations represent more or less distinct isolates.

Results: Microsatellites alone can have the power of detecting Asian contributions to the gene pool of populations now residing in Europe. Within Europe, a greater heterogeneity among populations sharing the same language than between populations sharing the same ethnic affiliation was found. There was low diversity and marked population differentiation in some Altaic speakers. Sympatry eroded inter-ethnic differentiation. No regular decline in genetic similarity with geography was seen.

Conclusion: Two layers of overall diversity represent a main feature of the genetic landscape of the population of the European portion of Russia.


April 07, 2010

Age and origin of 17q21 inversion in humans

Gene Expression has a comprehensive post on this inversion whose age had been estimated as 3-million years old, but was downgraded by a couple of orders of magnitude by the current study.

The polymorphism is found at its highest frequency in Southern Europe and Southwest Asia, but Razib argues in favor of its ultimately African origin because of its existence at a low frequency in the "isolated" Mbuti:
If H2 arose in the Middle East its presence in Africa could be explained by back-migration. I immediately was skeptical of this model because H2 is extant at frequencies of 5% among the Mbuti Pygmies. The Mbuti are relatively isolated genetically from the Bantu farmers who have come to dominate their region. If there was any group which represented the ancient genetic variation of Central Africa, it is likely the Mbuti.
While the Mbuti are indeed fairly isolated, it is not right to think of them as a relic of African genetic variation. The distinction is crucial: while the Mbuti contain a large component of "ancient" (pre-farming) African genetic diversity, they are by no means pure, as can be seen by last year's comprehensive study on African variation.

In other words: the Mbuti are a good population to find ancient African variation in; but, they also have admixture with more recent populations, which may have served as a conduit for the introduction of extraneous genetic elements such as the inversion in question.

Getting back to the paper itself, the moral is clear: be doubtful of genetic age estimates for extremely old events (by which I mean anything predating the Neolithic).

This includes the age estimate in this study which is based on microsatellites. The long-term behavior of these markers is based pretty much on conjecture, as we normally have the ability to observe them only across a few (human) generations.

So, I'm not taking as granted the accuracy of the current paper's age estimate. Nonetheless, the study of the distribution of the inversion is quite useful. Its origin is probably in West Asia, a region which would explain its presence in both Europe and Africa.

AJHG doi:10.1016/j.ajhg.2010.01.007

The Distribution and Most Recent Common Ancestor of the 17q21 Inversion in Humans

Michael P. Donnelly et al.


The polymorphic inversion on 17q21, sometimes called the microtubular associated protein tau (MAPT) inversion, is an ∼900 kb inversion found primarily in Europeans and Southwest Asians. We have identified 21 SNPs that act as markers of the inverted, i.e., H2, haplotype. The inversion is found at the highest frequencies in Southwest Asia and Southern Europe (frequencies of ∼30%); elsewhere in Europe, frequencies vary from less than 5%, in Finns, to 28%, in Orcadians. The H2 inversion haplotype also occurs at low frequencies in Africa, Central Asia, East Asia, and the Americas, though the East Asian and Amerindian alleles may be due to recent gene flow from Europe. Molecular evolution analyses indicate that the H2 haplotype originally arose in Africa or Southwest Asia. Though the H2 inversion has many fixed differences across the ∼900 kb, short tandem repeat polymorphism data indicate a very recent date for the most recent common ancestor, with dates ranging from 13,600 to 108,400 years, depending on assumptions and estimation methods. This estimate range is much more recent than the 3 million year age estimated by Stefansson et al. in 2005.


April 02, 2010

Little genetic differentiation in different language groups of the Cross River region of Nigeria

BMC Evolutionary Biology 2010, 10:92doi:10.1186/1471-2148-10-92

Little genetic differentiation as assessed by uniparental markers in the presence of substantial language variation in peoples of the Cross River region of Nigeria

Krishna R Veeramah et al.

Abstract (provisional)

The Cross River region in Nigeria is an extremely diverse area linguistically with over 60 distinct languages still spoken today. It is also a region of great historical importance, being a) adjacent to the likely homeland from which Bantu-speaking people migrated across most of sub-Saharan Africa 3000-5000 years ago and b) the location of Calabar, one of the largest centres during the Atlantic slave trade. Over 1000 DNA samples from 24 clans representing speakers of the six most prominent languages in the region were collected and typed for Y-chromosome (SNPs and microsatellites) and mtDNA markers (Hypervariable Segment 1) in order to examine whether there has been substantial gene flow between groups speaking different languages in the region. In addition the Cross River region was analysed in the context of a larger geographical scale by comparison to bordering Igbo speaking groups as well as neighbouring Cameroon populations and more distant Ghanaian communities.

The Cross River region was shown to be extremely homogenous for both Y-chromosome and mtDNA markers with language spoken having no noticeable effect on the genetic structure of the region, consistent with estimates of inter-language gene flow of 10% per generation based on sociological data. However the groups in the region could clearly be differentiated from others in Cameroon and Ghana (and to a lesser extent Igbo populations). Significant correlations between genetic distance and both geographic and linguistic distance were observed at this larger scale.

Previous studies have found significant correlations between genetic variation and language in Africa over large geographic distances, often across language families. However the broad sampling strategies of these datasets have limited their utility for understanding the relationship within language families. This is the first study to show that at very fine geographic/linguistic scales language differences can be maintained in the presence of substantial gene flow over an extended period of time and demonstrates the value of dense sampling strategies and having DNA of known and detailed provenance, a practice that is generally rare when investigating sub-Saharan African demographic processes using genetic data.


April 01, 2010

Archaeology magazine feature on Eleutherna

Dynasty of Priestesses is a nice Archaeology feature on a set of "Dark" age inhumations of females at the site of Eleutherna in Crete. There is plenty of audiovisual material on the site, so go ahead and visit it. An excerpt:
For a quarter century, Greek excavation director Nicholas Stampolidis and his dedicated team have been unearthing the untold stories of the people buried some 2,800 years ago in the necropolis of Orthi Petra at Eleutherna on Crete. Until now, the site has perhaps been best known for the tomb its excavators dubbed "A1K1," an assemblage of 141 cremated individuals, all but two of whom were aristocratic men who likely fell in battle in foreign lands. Excavated between 1992 and 1996, this elaborate rock-cut tomb was brimming with fantastic burial goods that date from the ninth to the seventh century B.C., including bronze vessels, gold and silver jewelry, and military regalia, as literally befits the burial of Homeric war heroes. Now, two unprecedented discoveries since 2007--three lavish jar burials that contained the remains of a dozen related female individuals and a monumental funerary building where a high priestess and her protégés, also all related, were laid to rest--are adding to our knowledge of Eleutherna's women, and forcing the scholarly community to reevaluate their importance and role in the so-called "Dark Ages" of Greece (see "Top 10 Discoveries of 2009").

There is also a nice long interview with anthropologist Anagnostis Agelarakis in which he makes an interesting conjecture about the different burial practice (inhumation vs. cremation) for women and men:
Let me explain my views as to why a cremation is, in essence, something that may be done out of necessity. The warriors may have died an honorable death in battle, miles and miles away from home. It would take days, possibly several weeks, even months for the rest of the comrades to come back from the war front. And what would happen to the dead during that time? So, they needed to be mourned and cremated there, in close proximity to the battlefield, as a comrade, a brother, a loved friend. Then their ashes had to be returned home safely. It's a lonely way to go for males, but also a very proper and functional way, I say. You return the dead home, you repatriate them. This is an important component, I believe, of the significance of this ancient Greek burial custom.

On the other hand, it is also not only possible but rather proper that a male warrior who passed on in his native land because of, let's say, a wound or old age would also be cremated, to pay respect and to honor his legacy and to help him join the others at the other side the same way they went. But females, they have a warmer, more familiar way. They have another kind of mighty and enduring network. They want to be together. Their physical bodies are buried together, so they're also together for sure in the afterlife. The funerary customs we observe at Orthi Petra and elsewhere aren't just a distinction of cultural norms arranged according to gender diversity. Their specific implementation also has roots in obligatory conditions directed or imposed by the circumstances of death.