Bones

John Hawks reports on Bones, a new TV drama series about forensic anthropologists. Inspired be real-life forensic anthropologist and writer Kathy Reichs.

The Myths of the 20th century

The first half of the 20th century was dominated by the myth of human inequality. According to this myth, human beings could be ordered in a scale of worth, with some individuals and groups being deemed superior and others inferior.

The second half of the 20th century was dominated by the myth of human identity. According to this myth, human beings were inherently the same, except for cosmetic external differences and the sexual differences necessary for procreation. Any observable differences in health, intelligence, personality, or beauty were deemed to stem from prejudices of the observer or the effects of environmental influences.

The first myth was a consequence of widespread means of transportation, which enabled the meeting of races and cultures. It was also a consequence of quantitative anthropology which enabled the measurement of human beings, and their classification according to measurable quantities such as the cephalic index or the facial angle.

The second myth was a result of the great emancipation movements. Previously marginalized groups, such as women and minorities found themselves in possession of the same rights as white males. It was believed that their previously socially inferior position would soon be changed, and that once people became unprejudiced and educated, then all genders and races would exhibit similar outcomes in life.

The myth of human inequality was the common-sense reaction to the previous Christian worldview of equality of men. People could no longer hold that view once faced with the dramatic differences in appearance, culture, and behavior between different groups. It was common-sense, but wrong, because human beings are not single-dimensional entities and cannot be ordered on a unique scale.

The myth of human identity was the moral reaction to the old society which subjugated a good portion of its population. It was wrong, because the power structures of society are not only the result of prejudice, oppression, and opportunity, but also a manifestation of innate differences between human individuals and groups.

Today, neither human inequality, nor human identity are any longer tenable positions. So, what will be our new myths for the 21st century?

Φόρουμ ΑΝΘΡΩΠΟΣ

Για τη διευκόλυνση της επικοινωνίας στα Ελληνικά όσων ενδιαφέρονται για θέματα ανθρωπολογίας, γενετικής, ιστορίας, κτλ. μπορείτε να συμμετάσχετε στις συζητήσεις στη διαδικτυακή κοινότητα ΑΝΘΡΩΠΟΣ. Προφανώς αρχικά δεν υπάρχουν αρκετά μέλη, αλλά ελπίζω πως με τον καιρό θα μαζευτούνε εκεί όσοι και όσες ενδιαφέρονται για φιλική συζήτηση πάνω σε αυτά τα αντικείμενα στην Ελληνική γλώσσα.

Were modern humans neighbors to Neanderthals?

A pretty good article on the controversy of modern human-Neanderthal interactions. The conventional orthodoxy that moderns and Neanderthals co-existed in Europe has been shaken by the fact that none of the Aurignacian archaeological assemblages, which were once believed to have been created by modern humans, are actually associated with modern human bones. So, the only way to associate them with modern humans is to claim that their sophistication makes it unlikely that they were created by Neanderthals, i.e., to presuppose that Neanderthals were dumber than modern humans and could not have created those artifacts. But, some of the Neanderthals' genes may persist in modern Europeans, so we shouldn't assume that Neanderthals were genetic dead-ends that had nothing (cultural or genetic) to offer to the first anatomically modern humans during their arrival in Europe.

On a somewhat related note, John Hawks writes about a recent conference on Rethinking the Human Revolution.

Ancient British mtDNA

One more paper added to the growing list of studies of ancient DNA. This time around, scientists have studied the mtDNA of Britons from the 4th to 11th century AD. The scope of the study is one of the largest I've seen so far, with 319 dental samples and 156 individuals in total. The haplogroup frequencies are shown below; the ancient sample is also split into Early and Late Saxon periods.



UPDATE

The comparative modern mtDNA were taken from the following regions. It is a bit peculiar that more continental European samples are missing, while Armenians and Palestinians are listed.

The comparative data set from modern populations of Europe for the founder and genetic distance analyses consisted of mtDNA HVS-I sequences from the following populations: Armenia (N=191), England (N=258), Estonia (N=149), northern France (N=101), Finland (N=176), Iceland (N=467), Norway (N=565), northern Germany (N=107), Palestine (N=117), Saami (N=176), Scotland (N=981), Spain (N=181) and Western Isles (N=181).

Molecular Biology and Evolution (advance access)

Tracing the Phylogeography of Human Populations in Britain Based on 4th-11th Century mtDNA Genotypes

A. Töpf et al.

Abstract

Some of the transitional periods of Britain during the first millennium AD are traditionally associated with the movement of people from continental Europe, composed largely of invading armies (e.g. the Roman, Saxon and Viking invasions). However, the extent to which these were migrations (as opposed to cultural exchange) remains controversial. We investigated the history of migration by women by amplifying mtDNA from ancient Britons who lived between approximately 300-1,000 AD, and compared these with 3,549 modern mtDNA database genotypes from England, Europe and the Middle East. The objective was to assess the dynamics of the historical population composition by comparing genotypes in a temporal context. Towards this objective we test and calibrate the use of rho-statistics to identify relationships between founder and source populations. We find evidence for shared ancestry between the earliest sites (predating Viking invasions) with modern populations across the north of Europe from Norway to Estonia, possibly reflecting common ancestors dating back to the last glacial epoch. This is in contrast with a late Saxon site in Norwich, where the genetic signature is consistent with more recent immigrations from the south, possibly as part of the Saxon invasions.

Link

Stop the presses... huge papers on brain evolution in recent humans

I am very sure that a set of new papers (one two) in Science will generate a huge amount of buzz. I will blog in more detail about them later, but for now, this Red Nova story covers the findings pretty well. The interesting part:

The team also observed geographic differences. For haplogroup D of ASPM, they found that it occurs more frequently in Europeans and surrounding populations including, North Africans, Middle Easterners, and South Asians, and at a lower incidence in East Asians, New World Indians and sub-Saharan Africans. For microcephalin, the researchers found that haplogroup D is more abundant in populations outside of sub-Saharan Africa.

For now, from the papers:



Fig. 3. Global frequencies of Microcephalin haplogroup D chromosomes (defined as having the derived C allele at the G37995C diagnostic SNP) in a panel of 1184 individuals.



Fig. 1. Worldwide frequencies of ASPM haplogroup D chromosomes (defined as having the derived G allele at the A44871G diagnostic polymorphism), based on a panel of 1186 individuals.

UPDATE

Here is what these studies mean:

• Microcephalin and ASPM are genes involved in regulating brain size
• A variant of Microcephalin has reached very high frequencies in non-Sub-Saharan Africans in the last 37,000 years.
  
• A variant of ASPM has reached very high frequencies especially in Caucasoids but also in some southern Mongoloids and Australoids in the last 5,800 years.
  
• It is almost inconceivable that these two factors were caused by random factors (drift). Therefore selection has acted on these two genes, favoring the new Microcephalin variant in non-Sub-Saharan Africans and the ASPM especially in Caucasoids, but also to a lesser extent in some southern Mongoloid and Australoid groups.
• We know absolutely nothing about what the new Microcephalin and ASPM variants actually do. What we do know is that they confer some substantial advantage that has caused them to grow in numbers. Perhaps, they confer some cognitive or behavioral ability.
  

These are the facts. The interpretation of the facts must wait until we have more information. However, the dates for the expansion of the two variants are extremely suggestive.

In a recent article, Erik Trinkaus has surveyed the human paleoanthropological record, and wrote that:

The earliest candidates for human anatomical modernity, those between ca. 150,000 and 195,000 years B.P. in Africa, are best considered as bridging a morphological gap between late archaic and early modern humans.

...

The spread of modern humans thoughout Africa and into Eurasia occurred after 50,000 years B.P. and probably after 40,000 years B.P., 100,000 years after their appearance.

Now, it may be a coincidence that the spread of humans throughout Africa and into Eurasia happened at around the same time that the new Microcephalin variant appeared, but the timing is certainly suggestive.

The question is: why did the new variant not get selected in Sub-Saharan Africans? There are only two possible explanations:

• There is something in the Sub-Saharan African environment which did not allow the variant to be selected; in other words: the variant did not confer an advantage in Africa itself.
• The gene pool of most Sub-Saharan Africans did not possess the new Microcephalin variant. Hence the variant did not get selected because it was lacking in the Sub-Saharan African gene pool.
  

Now, it is well known that the greatest difference in modern human genetic variation is between Sub-Saharan Africans and non-Sub-Saharan Africans. This is the result of the fact that humans originated in Africa, and possess only a subset of the variation that exists there.

As I have written before, there is good reason to believe that a human group originated in eastern Africa ("Afrasians") and came to colonize the rest of the world in relatively recent times. But, the rest of the African continent was already inhabited by pre-existing anatomically modern humans ("Paleoafricans") since at least 150,000 years in the past. These "Paleoafricans" were separated from the "Afrasians", as evidenced by the fact that typical "Paleoafrican" markers, originating long before the 40,000BP cutoff date, such as Y-haplogroups A and B and mtDNA haplogroups L0-L2 are not found in Eurasia.

If my theory is correct, then we don't need to propose some unquantifiable peculiarity of the African environment. Rather, the new Microcephalin variant has a low frequency in Sub-Saharan Africans precisely because it emerged in the Afrasians of eastern Africa that started colonizing the world around 40,000BP and was later added to the Paleoafrican populations of Sub-Saharan Africa. It simply has not had enough time to spread in most of Africa!

The second variant (of ASPM) is even more impressive, because it started to spread only 5,800 years ago, although the confidence margins are wide. The only movement which could have affected so many populations of Eurasia, regardless of language, in the last few millennia is the Neolithic expansion, followed by population growth in the first civilizations of the Near East and China.

It seems all by certain that the variant first appeared in Western Eurasia. It could have been carried easily to the east by the Near Eastern Neolithic people who reached India. It would only take a small step to make the jump to the Mongoloid world; once introduced into the population, it would also undergo the same selection process that made it so frequent among Caucasoids. However, agriculture begins much later among Mongoloids and even later among Australoids. So, the low frequency of the new variant in these populations is a consequence of the fact that it has had less time to spread among these populations.

The new ASPM variant is lacking in Sub-Saharan Africans and Native Americans. These results can be easily explained:

• Sub-Saharan African agriculture is late, and moreover there has been almost no gene flow from Eurasia into Sub-Saharan Africa, with a few occasional exceptions. So, the ASPM variant did not exist in the Sub-Saharan African gene pool, and could thus have not been selected.
• Native Americans migrated into the New World in Paleolithic times. Naturally, the ASPM variant was not present in their ancestral gene pool yet, so it could not have been selected.

The importance of these new papers is that cognitive evolution in Homo sapiens did not stop after our lineage became anatomically modern, and it did not stop when a subet of anatomically modern humans set out to colonize the world 40,000 years ago from eastern Africa, and it did not stop when Neolithic man appeared 10,000 years ago. Evolution has continued, and the proof for it is in the genetic variation of living human populations.

Science, Vol. 309 No. 5741

Microcephalin, a Gene Regulating Brain Size, Continues to Evolve Adaptively in Humans

Patrick D. Evans et al.

The gene Microcephalin (MCPH1) regulates brain size and has evolved under strong positive selection in the human evolutionary lineage. We show that one genetic variant of Microcephalin in modern humans, which arose ~37,000 years ago, increased in frequency too rapidly to be compatible with neutral drift. This indicates that it has spread under strong positive selection, although the exact nature of the selection is unknown. The finding that an important brain gene has continued to evolve adaptively in anatomically modern humans suggests the ongoing evolutionary plasticity of the human brain. It also makes Microcephalin an attractive candidate locus for studying the genetics of human variation in brain-related phenotypes.

Link

Ongoing Adaptive Evolution of ASPM, a Brain Size Determinant in Homo sapiens

Nitzan Mekel-Bobrov et al.

The gene ASPM (abnormal spindle-like microcephaly associated) is a specific regulator of brain size, and its evolution in the lineage leading to Homo sapiens was driven by strong positive selection. Here, we show that one genetic variant of ASPM in humans arose merely about 5800 years ago and has since swept to high frequency under strong positive selection. These findings, especially the remarkably young age of the positively selected variant, suggest that the human brain is still undergoing rapid adaptive evolution.

Link

Ancient subclades of mtDNA haplogroup M in northern island Melanesia

Proc Natl Acad Sci USA (published online)

Ancient mitochondrial M haplogroups identified in the Southwest Pacific

D. Andrew Merriwether et al.

Based on whole mtDNA sequencing of 14 samples from Northern Island Melanesia, we characterize three formerly unresolved branches of macrohaplogroup M that we call haplogroups M27, M28, and M29. Our 1,399 mtDNA control region sequences and a literature search indicate these haplogroups have extremely limited geographical distributions. Their coding region variation suggests diversification times older than the estimated date for the initial settlement of Northern Island Melanesia. This finding indicates that they were among the earliest mtDNA variants to appear in these islands or in the ancient continent of Sahul. These haplogroups from Northern Island Melanesia extend the existing schema for macrohaplogroup M, with many independent branches distributed across Asia, East Africa, Australia, and Near Oceania.

Link

Famous DNA

A compendium of published DNA results for famous people.

Serendipity

I had to take a picture...

Calabrians as Greek descenants

Before the Roman conquest, and for a long time afterwards, Calabria was Greek speaking. Greek speakers were descended from the Ancient Greek colonists, but also from medieval Greek settlements during the Byzantine era. Greek was widely spoken in very recent times, and even today there are few Greek-speaking survivors, speaking Griko, an Italian dialect of the Greek language.

Most of the Greeks of Calabrians are now Italianized, but it is very likely that due to the mostly rural conditions of the region, the absence of significant foreign settlements and the late survival of Greek, that they may be largely descended from the medieval Greeks of the region, and even before that, the Greeks of mainland Greece. Moreover, since Greek settlement in Calabria largely pre-dates the descents of Slavs and Albanians in Greece, we may be able to (roughly) determine the extent of the impact of these elements in the modern Greek population.

Two papers in the literature [1, 2] report on the frequency of Y-chromosome haplogroups in the population of Calabira. [1] reports data labeled as "Calabrians", and [2] reports data on the population of Reggio and Paola. The cumulative sample has a size of N=87. Frequency data are shown below, with Greek frequency data also shown for comparison from [3]



Of course, frequencies may be modified by random genetic drift, and Calabrians are not descended from all Greek regions, but we can still make some general observations about their commonalities and differences.

In both Calabrians and Greeks, haplogroup J2 appears to be very frequent, and haplogroup E3b is also very frequent. It appears very likely that these two haplogroups were represented in ancient populations.

Calabrians have a higher frequency of haplogroup R1b. This haplogroup originated in Asia, but its most recent expansions mark the movements of people from Iberia and Anatolia after the Last Glacial Maximum. Italians have a generally higher frequency of this haplogroup, and hence it appears likely that R1b in Calabrians may partially represent the contribution of native Italians to their gene pool.

Calabrians also have a higher frequency of haplogroup J1. This haplogroup originated in the southern part of the Fertile Crescent, and is often (but not exclusively) found in modern Semitic speakers such as Jews and Arabs. This may represent remnants of Near Eastern people during post-Roman times, even though its earlier arrival cannot be entirely excluded.

Finally, a striking feature of the frequency table is the paucity of R1a and I lineages in Calabrians. R1a originated in the Ukraine and spread after the Last Glacial Maximum, but more recently with Slavic speakers. I1b originated in the Balkans and spread during late Paleolithic and early Neolithic and subsequent times.

It is fairly interesting that in a study which included a Cypriot sample [4], only 2% of Cypriots carried haplogroup R1a chromosomes. Cypriots are also a population which separated from mainland Greeks before the medieval period. The frequency of haplogroup I chromosomes is not available for Cypriots.

Also, of interest is the fact that in regions of Anatolia [5] inhabited by Greek speakers until recently, and in which the native population may be assumed to be descended partially from Islamized Greeks, the frequencies of haplogroups R1a and I are also low. In the Aegean region (8) they are 3.3% and 6.7%, and in the eastern Black Sea region (3) where Muslim Greek speakers still exist, they are 4.8% and 2.4%. Moreover in Anatolia R1a1 frequency is correlated with longitude, declining towards Greece. R1a frequency also decreases from north to south in the Balkans [6].

In conclusion, this small survey provides some evidence against the notion that Y-haplogroups I and especially R1a were substantially represented in ancient Greeks. The relative absence of these haplogroups in populations thought to be partially descended from Greeks, in addition to the decrease in frequency of R1a both north-to-south in the Balkans and east-to-west in Anatolia are the main reasons for this observation.

Naturally, I doubt that we can statistically exclude the presence of either haplogroup -at some low frequency- in ancient Greeks using these relatively small samples, but at least we have some indication that they probably did not form a substantial part of their patrilineal descent.

Update

In a larger sample of Calabrians, the haplogroup I frequency is 5.4%, and that in Sicilians is 8.8% [7]. Haplogroup I lineages in the Balkans and Italy are divided mainly into I1a, I1b, and I*(xI1a, I1b).

Update 2

I also came across this interesting paper (Coll Antropol. 2001 Jun;25(1):189-93.) which further substantiates the idea of the genetic isolation of Reggio Calabria, listed as REG above:

Surnames of grandparents were collected from children in the primary schools of the Albanian-Italian, Croat-Italian, and Greek-Italian villages. The coefficients of relationships by isonymy show almost no relationship with ethnicity. Ethnolinguistic minorities of Southern Italy and Sicily are geographically subdivided in two main clusters: the first cluster comprises the Albanian, Croat, and Greek communities of the Adriatic area; and the second cluster comprises the Albanian communities of the Ionian, Thirrenian and Sicilian area. The Greeks of Reggio Calabria Province are completely separated from the other communities.

It would be extremely interesting to see a study that focused only on Greek speakers of Reggio Calabria.

References

[1] O. Semino et al., "The genetic legacy of Paleolithic Homo sapiens sapiens in extant Europeans: a Y chromosome perspective", Science, 290(5494): 1155-1159.
[2] F. Di Giacomo et al., "Clinal patterns of human Y chromosomal diversity in continental Italy and Greece are dominated by drift and founder effects." Molecular Phylogenetics and Evolution, 28(3): 387-395.
[3] C. Flores et al., "Isolates in a corridor of migrations: a high-resolution analysis of Y-chromosome variation in Jordan", Journal of Human Genetics (in press).
[4] Z. Rosser et al., "Y-Chromosomal Diversity in Europe Is Clinal and Influenced Primarily by Geography, Rather than by Language", American Journal of Human Genetics, 67(6): 1526-1543.
[5] C. Cinnioglu et al., "Excavating Y-chromosome haplotype strata in Anatolia", Human Genetics 114(2): 127–148.
[6] M. Pericic et al., "High-Resolution Phylogenetic Analysis of Southeastern Europe (SEE) Traces Major Episodes of Paternal Gene Flow Among Slavic Populations", Molecular Biology and Evolution (in press).
[7] S. Rootsi et al., "Phylogeography of Y-chromosome haplogroup I reveals distinct domains of prehistoric gene flow in europe", American Journal of Human Genetics 75(1): 128-37.

Jordanian Y chromosomes

New paper on Y chromosomes in Jordan, showing how the smoothness of macro-scale genetic variation often finds significant deviations at the more micro-scale level. It is imperative that such studies be conducted in more Near Eastern populations so that we can understand better the origin and evolution of Caucasoids in the region.

The Y-haplogroup frequency table is also interesting because it lists frequency of haplogroups in several populations. Greek frequency data are compiled from the literature and appear in the final column, and allow us to quantify the non-Caucasoid admixture in Greeks (0.2% Sub-Saharan haplogroup A and 1.3% Asian haplogroup C; total 1.5%). Haplogroup B (0.2%) reported in Greeks in the table is an error (see update below).



Update:

I contacted the authors of the study, pointing out that haplogroup B did not occur in the studies used to obtain results for the Greek population, and they have confirmed that this is the case:

Thank you for your careful revision of our article about Y chromosome in Jordan. Yes, you are right. There is a mistake in table 1. The greek B haplotypes are in fact indeterminated Y*.
We apologize for this error.
Sincerely yours,

A.M. González
e-mail: amglez@ull.es

Journal of Human Genetics (Online early)

Isolates in a corridor of migrations: a high-resolution analysis of Y-chromosome variation in Jordan

Carlos Flores et al.

Abstract A high-resolution, Y-chromosome analysis using 46 binary markers has been carried out in two Jordan populations, one from the metropolitan area of Amman and the other from the Dead Sea, an area geographically isolated. Comparisons with neighboring populations showed that whereas the sample from Amman did not significantly differ from their Levantine neighbors, the Dead Sea sample clearly behaved as a genetic outlier in the region. Its high R1*-M173 frequency (40%) has until now only been found in northern Cameroonian samples. This contrasts with the comparatively low presence of J representatives (9%), which is the modal clade in Middle Eastern populations, including Amman. The Dead Sea sample also showed a high presence of E3b3a-M34 lineages (31%), which is only comparable to that found in Ethiopians. Although ancient and recent ties with sub-Saharan and eastern Africans cannot be discarded, it seems that isolation, strong drift, and/or founder effects are responsible for the anomalous Y-chromosome pool of this population. These results demonstrate that, at a fine scale, the smooth, continental clines detected for several Y-chromosome markers are often disrupted by genetically divergent populations.

Link

Population growth or selective sweep (Part II)

In Population growth or selective sweep I reported on a recent Current Anthropology article which addressed the issue of whether current human mtDNA variation is best interpreted as a signal of a population expansion from a small founder population or the successful remainder of a selective sweep.

John Hawks, who advocates the selection hypothesis has responded to the article with a blog post titled Selection, nuclear genetic variation, and mtDNA. This should highlight the controversial nature of the subject, and the fact that we are far from reaching a consensus.

Personally, I have always been somewhat skeptical of the idea that much can be learned about our most ancient past from genetic variation in modern populations. Modern populations are the result of so many evolutionary processes involving selection, drift, and intermixture, both in Paleolithic and most recent (and more tumultuous) Neolithic-historical times.

Genetic models seem to be fairly inadequate to capture the richness of human prehistory, as they more often than not tend to be fairly simple, with a lot of "best guesses" given to critical parameters. This has led to at least one palaeoanthropologist (Erik Trinkaus) proposing that we should do away with them altogether:

The analyses of extant human molecular data generally have little biologically relevant statistical power (whatever probability values their statistical computations may generate); most analyses use analytical algorithms whose biological assumptions and appropriateness are unstated, untested, and frequently untestable; many assume demographic stability over the past 50,000–200,000 years (see above); most consider the human populational dynamics of the past 30 millennia to have been trivial; many use distance statistics and graphic techniques (such as dendrograms), which deny the reticulate nature of human population evolution (hence assuming replacement); a number of them invoke molecular clocks whose reliability and precision within the time period of concern is undemonstrated and/or whose calibration (based on the fossil record) is simply wrong; and many employ living human samples of opportunity when those samples have biases relative
to the issue of modern human origins. And finally, all of them have a real-time depth of perhaps a century, and the interpretations based on those data are dependent on their analytical assumptions. This last point is evident in the large number of articles concerned more with the analytical techniques and their assumptions than with interpreting the available data.

It would be heartening to think that things are better in palaeoanthropology, but non-genetic factors affecting morphology, significant dating uncertainties, unavailability of key fossils for study, as well as the largely spotty record (a few skulls over tens of thousands of years) probably make that field as unreliable as genetics.

Perhaps we don't yet have either the data or the tools to make authoritative inferences about our origins quite yet, but the process is certainly interesting!

Portuguese Y chromosomes

A new paper in Annals of Human Genetics studies Portuguese Y chromosomal distribution from several locations around the country, demonstrating relative homogeneity, with an exception of a single outlier population.

Annals of Human Genetics (online early)

Micro-Phylogeographic and Demographic History of Portuguese Male Lineages

Sandra Beleza et al.

Abstract

The clinal pattern observed for the distribution of Y-chromosome lineages in Europe is not always reflected at a geographically smaller scale. Six hundred and sixty-three male samples from the 18 administrative districts of Portugal were typed for 25 Y-chromosome biallelic and 15 microsatellite markers, in order to assess the degree of substructuring of male lineage distribution. Haplogroup frequency distributions, Analysis of Molecular Variance (AMOVA) and genetic distance analyses at both Y-SNP and Y-STR levels revealed a general genetic homogeneity of Portuguese sub-populations. The traditional division of the country in north, central and south, which is usually considered in studies addressing questions of the genetic variation distribution in Portugal, was not reflected in the Y-haplotype distribution. Instead, just one sub-region (Alentejo) stood out due to the presence of high diversity levels and a higher number of different lineages, at higher frequencies than in other regions. These results are reconciled with the historical evidence available, assuming that from prehistorical times down to the end of the medieval period this region harboured the most diverse groups of people and, because of economic depression, remained relatively isolated from recent homogenisation movements. The finding of a broadly homogeneous background for the Portuguese population has vast repercussions in forensic, epidemiological and association studies.

Link

Heath-Carter somatotyping method

Somatotyping, pioneered by William Sheldon in the 1940s is the description of body type based on three components of endomorphy ("fatness"), mesomorphy ("muscularity"), and ectomorphy ("thinness"). A somatotype is usually given as a composite of three numbers, e.g., 711, where each number demonstrates the strength of one of the three components. The most widely used somatotyping method today is that of Heath and Carter. You can read an instruction manual for somatotyping online in pdf form.

Black Indians

Great article from Wired on the descendants of black freedmen who seek membership in Native American tribes, in part due to the economic gain of membership, with an emphasis on genetic testing to determine whether or not they have Native American ancestry. Of course, as stated in the article by Dr. Tony Frudakis, it is possible for a Greek or Pakistani to show a high proportion of Native American "heritage". Anomalous results such as these would render this avenue of testing almost useless for the purpose of establishing Amerindian descent.

Population growth or selective sweep?

A new article in Current Anthropology revisits the issue of the contribution of Neandertals to the modern human gene pool. Two issues are considered: first, is Neandertal mtDNA really that distinctive from modern human mtDNA? second, is the relative homogeneity of modern human DNA the result of a selective sweep or of rapid population growth. With regard to the first question, the authors have this to say:

Is Neandertal mtDNA actually so distinctive? One basic assumption of our simulations is that Neandertal mtDNA lineages are distinct relative to the variation found in living humans. The initial studies by the Neandertal mtDNA sequencing groups found that living human and Neandertal sequences differed substantially from each other (Krings et al. 1997, 2000; Ovchinnikov et al. 2000; Schmitz et al. 2002). A reanalysis by Gutiérrez, Sánchez, and Marín (2002) did conclude that Neandertal mtDNA was within the range of living human variation, but this result may have been an artifact of bootstrapping sequences to generate neighbor-joining trees with a rapidly evolving genetic system such as mtDNA, in which the ratio of noisy (i.e., highly inconsistent or homoplastic) to stable sites is high. This approach may create many neighbor-joining trees whose topology is determined primarily by inconsistent sites, so by chance some living humans and Neandertals sometimes group together to the exclusion of other living humans (A. Knight, personal communication). In contrast, Caramelli et al. (2003) found no overlap between modern human and Neandertal mtDNA sequences using multidimensional scaling, and along with living human sequences this analysis included possible (because contamination cannot be ruled out) ancient modern human sequences from Paglicci 12 and 25, Italy (P12 and P25), and Lake Mungo 3, Australia (LM3). Knight (2003) used a phylogenetic approach to Neandertal mtDNA and found four highly consistent synapomorphies that unite Neandertals to the exclusion of all living humans and four highly consistent synapomorphies that unite all living humans to the exclusion of Neandertals (a total of eight highly consistent sites that define the two clades, including an insertion, which is a very rare event). These eight sites are consistent across thousands of living humans and are known to have low mutation rates. Additionally, for preserved sites, the mtDNA sequences from P12 and P25, LM3, and the nuclear mitochondrial insert (thought to have diverged shortly before the oldest coalescence of living human mtDNA sequences [Zischler et al. 1995]) have none of the Neandertal synapomorphies while possessing all of the diagnostic derived sites of living human sequences (A. Knight, personal communication). Recently, mtDNA fragments were extracted from four additional Neandertal and five early modern human fossils that had similar biomolecular preservation. All the Neandertals and none of the ancient modern humans yielded sequences similar to previous Neandertal sequences (Cooper, Drummond, and Willerslev 2004, Serre et al. 2004). It appears, therefore, that the assumption that Neandertal mtDNA is distinct from that of living humans is reasonable.

The second question is quite interesting. The fact that modern human mtDNA is similar to each other and differs from Neandertal mtDNA can be explained in either of two ways: (i) modern humans and Neandertals were two separate lineages evolving on their own, or (ii) modern human mtDNA is the product of selection, i.e., modern humans possess only those mtDNA types that have survived a selective sweep. The implication of this is that formerly, humans had much different mtDNA types which no longer exist because they were culled by natural selection.

The "rapid population growth" model suggests that the relative homogeneity of human mtDNA is the result of the fact that until a few tens of thousands years ago, humans formed a small population, with relatively little mtDNA diversity. Hence, our current mtDNA diversity is due to the fact that even though we now number in the billions, we are still ultimately descended from a small group of individuals in the not-so-distant past. This model contrasts with the "selective sweep" model, in which our genetic diversity is a remnant of past genetic diversity over a long period of time, the remnant that has survived the selective sweep. The authors review the evidence, and suggest that the "rapid population growth" model explains the data better than the alternative:

The significance of ancient Neandertal mtDNA for resolving the fate of Neandertals increases greatly when considered in light of models for modern human origins derived from archaeology. On the basis of mtDNA, if Neandertals survived late in Europe, their per generation contribution to early modern human populations must have been fairly small (<0.2%).Archaeology tends to support the rapid population growth model (Klein et al. 2004, Stiner et al. 1999), as does living human mtDNA (Excoffier and Schneider 1999, Ingman et al. 2000). Other genetic regions are more equivocal about the timing and magnitude of population growth (Harpending and Rogers 2000, Ptak and Przeworski 2002, Wall and Przeworski 2000), but recent studies of SNPs and microsatellites appear to be reaching a consensus consistent with the results for mtDNA (Marth et al. 2004, Zhivotovsky, Rosenberg, and Feldman 2003). Our results stress the importance of fully integrating archaeological, fossil, and genetic evidence in investigations of modern human origins.

This earlier post on human-Neanderthal admixture, estimated at less than 0.1% is also of interest.

CURRENT ANTHROPOLOGY Volume 46, Number 4, August-October 2005

Ancient DNA, Late Neandertal Survival, and Modern-Human Neandertal Genetic Admixture

Timothy D. Weaver and Charles C. Roseman

(No abstract)

Link