Over at Harappa DNA Zack ran ChromoPainter/fineStructure on his South Asian data set and posted the results. The new method immediately makes a few things clear:

1) The “South Asians” in the HGDP data set that’s been used for so long are rather on the inbred side, and relatively genetically distinct as far as South Asian populations go. It goes to illustrate the importance of finely calibrating geographic coverage, and the consequences of the “Permit Raj.”

2) Some of the Gujarati individuals in the HapMap also shake out as a moderately tight group (the square in the middle of the graphic above). Not too surprising, but rather striking. Another illustration of the importance of selecting representative and informative populations for any given region.

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In The New York Times, DNA Turning Human Story Into a Tell-All:

The tip of a girl’s 40,000-year-old pinky finger found in a cold Siberian cave, paired with faster and cheaper genetic sequencing technology, is helping scientists draw a surprisingly complex new picture of human origins.

The new view is fast supplanting the traditional idea that modern humans triumphantly marched out of Africa about 50,000 years ago, replacing all other types that had gone before.

Instead, the genetic analysis shows, modern humans encountered and bred with at least two groups of ancient humans in relatively recent times: the Neanderthals, who lived in Europe and Asia, dying out roughly 30,000 years ago, and a mysterious group known as the Denisovans, who lived in Asia and most likely vanished around the same time.

Their DNA lives on in us even though they are extinct. “In a sense, we are a hybrid species,” Chris Stringer, a paleoanthropologist who is the research leader in human origins at the Natural History Museum in London, said in an interview.

First, for reasons of novelty we are emphasizing the exotic tendrils of the human family tree. Even Chris Stringer, the modern paleontological father of “Out of Africa,” is claiming we’re hybrids! But let’s not forget that non-Africans are the product of a very rapid radiation out of the margins of the Afrotropic ecozone within the last ~50-100,000 years. I am not entirely sure that this is as true of Africans (recall how extremely basal Bushmen are to the rest of humanity; they seem to have diverge well before the “Out of Africa” pulse).

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The Pith: New software which gives you a more fine-grained understanding of relationships between populations and individuals.

According to the reader survey >50 percent of you don’t know how to interpret PCA or model-based (e.g., ADMIXTURE) genetic plots, so I am a little hesitant to point to this new paper in PLoS Genetics, Inference of Population Structure using Dense Haplotype Data, as it extends the results of those earlier methods. But it’s an important paper, and at some point I’ll starting using their software. The “big picture” is that earlier methods left “some information on the table.” That’s partly due to the fact that they were developed (or in the case of PCA leveraged, as it’s a very general technique) in an era where very dense marker data sets were not available (today we’re shifting to full genome sequences in many cases!). The information left on the table would be haplotype structure. Genetic variation in a concrete form manifests as sequences along a line, many of them physically connected. These correlations of nearby variant markers represent haplotypes of great interest, because they are excellent clues to admixture or divergence events across populations. In contrast the older methods, were looking at variation from marker to marker, each in turn independently, which collapses some of the important genomic structure that we can now inspect (in fact, linkage disequilibrium due to these correlations can distort some of the results in the older methods, so you want to “thin” your marker set).

Let me make this concrete for you. On 23andMe you can see where your friends shake out on a PCA plot using the HGDP data set as a reference. What this means is that the HGDP data set is used to generate independent dimensions of genetic variation. As is the usual case in these analyses the largest dimension separates Africans from everyone else, and the second largest dimension separates Asians from Europeans and Africans. 23andMe customers are then projected upon this variation, so you can get a sense where you are positioned in the clusters. To the left is a zoom in on the section for Central/South Asians. You can see that one of my friends, highlighted with a green color, falls almost perfectly in the Uygur cluster. According to ancestry estimates my friend is 50 percent Asian and 50 percent European. The “representative” Uygur in the 23andMe chromosome painting gives about the same results. But these are total genome estimates. The historical nature of my friend’s admixture and that of the Uygur woman is very different, as one can see in the below figure.

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The excellent site io9 has a piece up today which is a fascinating indicator of the nature of popular science publications as a lagging indicator. It is a re-post of a piece published last April, How Mitochondrial Eve connected all humanity and rewrote human evolution. In it you have an encapsulation of a particular period in our understanding of human natural history through evolutionary genetics. Notice for example the focus on maternally transmitted lineages, mtDNA and Y chromosomes. And the citations on genealogy date to the middle aughts. The science is mostly correct as far as it goes in the details (or at least it is defensible, last I checked there was still debate as to the validity of the molecular clocks used for Y chromosomal lineages), but it misses the big picture of how we’ve reframed our understanding of the human past over the last few years. The distance between 2011 and 2009 is far greater in this sense than between 2009 and 1999 (or even 2009 and 1989!). The io9 piece is a reflection of the era before the paradigmatic rupture.

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With DNA Testing, Suddenly They Are Family:

Several companies provide tests that can confirm whether adoptees are related to individuals they already know. Others cast a wider net by plugging DNA results into databases that contain tens of thousands of genetic samples, provided mostly by people searching for their ancestral roots. The tests detect genetic markers that reveal whether people share a common ancestor or relative.

Some experts on adoption and genetics have criticized ancestry and genealogy testing companies, saying they are, at times, connecting people whose genetic links are tenuous — in effect stretching the definition of a relative. Nevertheless, the growing popularity of the tests, combined with social media sites that connect people day to day, has given some adoptees a sense of family that feels tangible, intimate and immediate.

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Apparently the national media is reporting that scientific genealogy may result in leads to a cold case. The principle is simple: apparently Y chromosomal material was matched to public genealogy databases. From this the researcher concluded that the perpetrator is probably a male line descendant of Robert Fuller of Salem, Massachusetts. Contrary to the urban legends it does not seem that false paternity rates are much higher than ~1 percent in many societies (for example).

CeCe Moore and Blaine Bettinger have covered this story in detail, so I won’t go much further in this specific case. But as more and more people get typed and sequenced I suspect that genetic material is going to be more and more “actionable.” What long term effects will this have? Will criminals start taking precautions?

I have blogged about the genetics of altitude adaptation before. There seem to be three populations in the world which have been subject to very strong natural selection, resulting in physiological differences, in response to the human tendency toward hypoxia. Two of them are relatively well known, the Tibetans and the indigenous people of the Andes. But the highlanders of Ethiopia have been less well studied, nor have they received as much attention. But the capital of Ethiopia, Addis Ababa, is nearly 8,000 feet above sea level!

Another interesting aspect to this phenomenon is that it looks like the three populations respond to adaptive pressures differently. Their physiological response varies. And the more recent work in genomics implies that though there are similarities between the Asian and American populations, there are also differences. This illustrates the evolutionary principle of convergence, where different populations approach the same phenotypic optimum, though by somewhat different means. To my knowledge there has not been as much investigation of the African example. Until now. A new provisional paper in Genome Biology is out, Genetic adaptation to high altitude in the Ethiopian highlands:

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Update: If interested, please email me at contactgnxp -at- gmail -dot- com. Also, I am getting some feedback via 23andMe that people with white South African matches noticed Africa segments in many of the ancestry paintings. This has definitely increased by probability that the admixture proportion is ~5 percent. There will probably be a few genotypes coming in shortly, but I am going to see if I can get more people typed (fundraising appeal pending!).

It’s been a while since I’ve gone looking for genotypes of particular ethnic groups. The results were rather good for the Tutsi and Malagasy. So I thought I’d venture out again, despite being a bit busy. Here’s what I want: the genotype of an Afrikaner (or several). A few years ago South African geneticist J. M. Greeff did an analysis of his own pedigree, and estimated that he had ~6 percent non-European ancestry (he did validate this with some genetic markers; e.g., his father’s mtDNA is of the M haplogroup, which is almost always Indian). This is in line with other genealogists who have estimated, about 5 percent non-European heritage. How much should we trust these non-biological studies? The genomic estimates of African American ancestry being ~20 percent European were anticipated by analyses of family histories from text records, so we certainly shouldn’t dismiss them (in fact, it seems possible that these analyses will underestimate non-European ancestry because of cryptic individuals in the pedigrees).

And we have plenty of records of people of non-European ancestry contributing to the Afrikaner population in any case. Greeff found the records for his own pedigree, but the first Governor of the Dutch Cape Colony was himself of mixed-race (his mother was Eurasian). The question is is a matter of degree. Are Afrikaners like American whites, with hardly any non-European ancestry (~1 percent or less), or like Latin American whites, with significant non-European ancestry (~5 to 20 percent)? My own bet is that they’ll be in the middle. The proportion of non-European ancestry is low enough that individuals such as Sandra Laing are very rare indeed. But if the 5 percent estimate is valid, and almost of all these ancestors were women, then a larger proportion of the mtDNA is going to be non-European.

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Randy McDonald points me to this fascinating post, Genetic clues to the Ossetian past. In the post author outlines phylogeographic inferences one can make from uniparental lineages; maternal and paternal lines of descent. Specifically, they are in interested in the origins and relationships of the Ossete people. I assume that one reason Randy pointed me to this post is that the Ossetes are assumed by many to be the descendants or fragments of the Alans. More broadly they’re remnants of a broad array of North Iranian peoples, of whom the Scythians were the most prominent, which have been erased from the pages of history because of the expansion of the Slavs and Turks.

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The idea of a “folk wandering” was once a well accepted idea in history, in particular for the phase of the Late Roman Empire, and the subsequent fall of the Western Empire. It’s a rather simple concept: the collapse of the Pax Romana occurred simultaneous with a mass ethnic reordering of Europe, primarily via the migration of Germanic peoples across its frontiers and beyond. The most extreme depictions of this can be found in the works of the British cleric Gildas: German hordes literally drove the British into the sea, until they only retained their redoubts around the “Celtic Fringe.”

This was an extreme understanding of the dynamics of post-Roman Europe. It was, and has been, succeeded by another extreme model: that the ethnic change in the post-Roman world was more illusion than substance, a manner of shifting nomenclature, than lineage. For example, I have commonly read in this literature that the Germanic tribes which crystallized as “federates” to the Romans, or on occasion as antagonists (or vassals to hostile powers such as the Huns) were ad hoc collections of mercenaries who created an identity de novo.  In some cases it is posited that masses of Romans simply assimilated to the identity of a small cadre of warriors whose demographic impact was trivial. This is the scenario that is posited for the transformation of Celtic Britain into Germanic England. But let’s shift away from that extreme case, and look at another one: the 5th and early 6th century kingdom of the Vandals in Norh Africa.

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Michelle points me to this article in The Lost Angeles Times, The Colors of the Family:

I was holding my 1-year-old, ambling about downtown with some friends. White friends. She must have thought my boy belonged to one of them.

There’s a simple explanation: I’m black but my son, Ashe, is white. At least he looks it.

But things are more complicated than that.

I’m actually half black and half white. It should come as no surprise, though, that even as sophisticated as we’ve become about people of mixed parentage, I’m pigeonholed as black. If someone asks and I don’t have time to go deeper, that’s what I call myself.

Ashe is mixed too. His mother, my wife, Vanashree, is half white and half South Asian, with roots in India. She has olive skin, and Ashe is slightly lighter than she is.

This surprised us. When Ashe was born, one of the first things I said to Vanashree was, “Honey, he’s so light!” We chuckled, poking fun at our assumptions.*

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In the near future I will be analyzing the genotype of an individual where all four grandparents have been typed. But this got me thinking about my own situation: is there a way I could “reconstruct” my own grandparents? None of them are living. The easiest way to type them would be to obtain tissue samples from hospitals. This is not totally implausible, though in this case these would be Bangladeshi hospitals, so they might not have saved samples or even have a good record of hem. Another way would be to extract DNA from the burial site. This is not necessarily palatable. But assuming you did this, if you have access to a forensic lab it might be pretty easy (though I think most forensic labs using VNTRs, rather than SNP chips, so I don’t know if they’d touch every chromosome), I’m not sure that the quality would be optimal for more vanilla typing operations, especially for older samples which are likely to be contaminated with a lot of bacteria.

For me the simplest option is to look at relatives. Each of my grandparents happens to have had siblings, so there are many sets of relatives related to just each of those individuals of interest. I also have many cousins, so pooling all the genotypes together and using the information of a pedigree one could ascertain which chromosomal segments are likely to derive from a particular grandparent. To give a concrete example, my mother has a maternal cousin to whom she is quite close. By typing my mother and her cousin one could infer that the segments shared across the two individuals derive from the common maternal grandparents. Of course there’s a problem that cousins have a coefficient of relatedness of only 1/8th, so there is going to be a lot of information missing. But, if you had lots of cousins you could presumably reconstruct the genotypes far better.

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Zinedine Zidane, a Kabyle

There is a new paper in PLoS Genetics out which purports to characterize the ancestry of the populations of northern Africa in greater detail. This is important. The HGDP data set does have a North African population, the Mozabites, but it’s not ideal to represent hundreds of millions of people with just one group. The first author on this new paper is Brenna Henn, who was also first author on another paper with a diverse African data set. Importantly the data was posted online. Unfortunately though most of the populations didn’t have too many markers. This isn’t an issue in an of itself, but it becomes a big deal when trying to combine it with other data sets. If you limit the markers to those which intersect across two data sets you start to thin them down a lot, to the point where they’re not useful. Though the the results of the paper are worth talking about, the authors claim that they’ll be putting the data online. This is important because they used a large number of markers, so the intersections will be nice (I can, for example, envisage exploring the relationship between the North Africans and the IBS Iberian sample in the near future).

As for the paper itself, Genomic Ancestry of North Africans Supports Back-to-Africa Migrations:
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Please see Luke Jostins’ posts at Genetic Inference and Genomes Unzipped.

Update: Steve Hsu weighs in. He read the supplements! Mad props.

Sad news. John Hawks passes along that James F. Crow has died. Further mention from the National Center For Science Education. A little over 5 years ago I sent Crow an email with only minimal expectation of response, asking about an interview. He responded in less than 24 hours! I think it says a lot about the man that he would respond to sincere questions out of the blue from basically a nobody. Here is his Wikipedia entry. And remember that Genetics has commissioned a series of retrospective essays in Crow’s honor.