Population Substructure
razib | March 4, 2010A new paper in PLoS, Rapid Assessment of Genetic Ancestry in Populations of Unknown Origin by Genome-Wide Genotyping of Pooled Samples:
Many association studies have been published looking for genetic variants contributing to a variety of human traits such as obesity, diabetes, and height. Because the frequency of genetic variants can differ across populations, it is important to have estimates of genetic ancestry in the individuals being studied. In this study, we were able to measure genetic ancestry in populations of mixed ancestry by genotyping pooled, rather than individual, DNA samples…
razib | February 16, 2010Lactase persistence results in the ability to break down the lactose sugar in milk as an adult, lactase being the enzyme which breaks down lactose. If one can not digest that sugar, and still consumes milk, then one exhibits the symptoms of lactose intolerance. Originally diagnosed as a disease it has come to light that 2/3 of the world's population is lactose intolerant, and, that this is probably the ancestral "wild type" (I would be interested if readers could name a mammal which exhibited lactase persistence aside from humans). Lactase persistence is a relatively new trait which emerged…
razib | January 12, 2010A week ago I pointed out that in some visualizations of world wide population variation South Asians & mestizos seem to overlap which each other to a great extent. The reason for this is that both populations can be modeled as admixtures between two separate, but related, populations. Mestizos are the products of pairings between Europeans and indigenous America populations, while South Asians seem to be a stabilized hybrid population which emerged from the fusion of a West Eurasian (closely related to European) and East Eurasian (distantly related to East Asians) populations. The East…
razib | December 15, 2009That's probably the big takeaway of a new paper on the genetics of Asians, a set which includes South Asians, but in the new research mostly focuses on the people of East Asia. In a global context this work is important. The backstory is that there are disagreements about the exact process of the "Out of Africa" migration. Most researchers would agree that the vast majority, perhaps all, of the distinctive genetic content of the human species derives from a migration from the African continent between 50 and 100 thousand years ago (closer to the former date than the latter likely). Note that…
razib | December 9, 2009According to search engine traffic one of the most popular posts on this weblog has to do with the genetic background of Ashkenazi Jews. That is, those Jews whose ancestors derive from Central & Eastern Europe, and the overwhelming number of Jews in the United States. The genetic origins of this group are fraught with politics naturally. With the rise of biological science the characteristics of Jews were used as a way to differentiate them as a nation apart in more than a cultural and religious sense. After World War II other researchers attempted to show that Jews were not genetically…
razib | December 5, 2009About six months ago I had a post up on the Cape Coloureds of South Africa. As a reminder, the Cape Coloureds are a mixed-race population who are the plural majority in the southwestern Cape region of South Africa. Like the white Boers they are a mostly Afrikaans speaking population who are adherents of Reformed Christianity. After the collapse of white racial supremacy many white Afrikaners have argued that it is natural and logical to form a cultural alliance with the Cape Coloureds because of the affinity of language and faith (Afrikaans speaking Coloureds outnumber Afrikaans speaking…
razib | November 25, 2009The state of China has 1/5 of humanity within its borders, so it's genetic structure is of interest. It is obviously important for medical reasons to clarify issues of population structure so that disease susceptibility among the Han is well characterized, in particular with the heightened medical needs of an aging population in the coming generation. And of course, there are the nationalistic concerns. About 20 years ago L. L. Cavalli-Sforza reported that his South Chinese samples were genetically closer to Southeast Asians than North Chinese in The History and Geography of Human Genes.…
razib | November 24, 2009A new paper in PLoS ONE, Evaluation of Group Genetic Ancestry of Populations from Philadelphia and Dakar in the Context of Sex-Biased Admixture in the Americas, doesn't add much to what we know. They looked at a several hundred individuals who are self-identified as African American and European American, as well as 49 Senegalese from Dakar. Additionally, they reanalyzed data from Latin America from whites and blacks in Brazil, as well as a group of mixed Cubans. They found what you might expect to find, African and Native ancestry shows a female bias, European ancestry shows a male bias.
But…
razib | October 25, 2009When Mendelism reemerged in the early 20th century to become what we term genetics no doubt the early practitioners of the nascent field would have been surprised to see where it went. The centrality of of DNA as the substrate which encodes genetic information in the 1950s opened up molecular biology and led to the biophysical strain which remains prominent in genetics. Later, in the 1970s Alan Wilson and Vincent Sarich used crude measures of genetic distance to resolve controversies in paleontology, specifically, the date of separation between the human and ape lineage. Genetics spans the…
razib | October 10, 2009Dienekes points to a new paper which attempts to quantify the genetic ancestry of South Asian Muslims into indigenous and exogenous components:
Islam is the second most practiced religion in India, next to Hinduism. It is still unclear whether the spread of Islam in India has been only a cultural transformation or is associated with detectable levels of gene flow. To estimate the contribution of West Asian and Arabian admixture to Indian Muslims, we assessed genetic variation in mtDNA, Y-chromosomal and LCT/MCM6 markers in 472, 431 and 476 samples, respectively, representing six Muslim…
razib | August 29, 2009Dienekes points me to a new paper, European Population Genetic Substructure: Further Definition of Ancestry Informative Markers for Distinguishing Among Diverse European Ethnic Groups. You've seen this song & dance before:
Population substructure in Japan
Population substructure of Mexican Mestizos
European population substructure
Genetic Map of East Asia
The genetics of Fenno-Scandinavia
Finns as European outliers
Uyghurs are hybrids
Genetic structure of Eastern European populations
Genetic map of Europe; genes vary as a function of distance
More genetic maps of Europe
Human population…
razib | July 30, 2009An ancestry informative marker set for determining continental origin: validation
and extension using human genome diversity panels:
Results
In this study, genotypes from Human Genome Diversity Panel populations were used to further evaluate a 93 SNP AIM panel, a subset of the 128 AIMS set, for distinguishing continental origins. Using both model-based and relatively model-independent methods, we here confirm the ability of this AIM set to distinguish diverse population groups that were not previously evaluated. This study included multiple population groups from Oceana, South Asia, East…