genetic structure
razib | March 16, 2010Dienekes has reposted some of the abstracts from the meeting of the American Association of Physical Anthropologists. This one caught my eye, Genetic analyses reveal a history of serial founder effects, admixture between long separated founding populations in Oceania, and interbreeding with archaic humans:
Genetic anthropologists continue to debate whether human neutral genetic variation primarily reflects a continuum of demes connected by local gene flow or colonization and serial founder effects. A second unresolved issue concerns the genetic contribution of archaic species to the modern…
razib | February 10, 2010Interesting that I just pointed to Neandertal DNA, a really big story just came out on ancient Greenlander genetics, Whole Genome of Ancient Human Is Decoded:
The genome of a man who lived on the western coast of Greenland some 4,000 years ago has been decoded, thanks to the surprisingly good preservation of DNA in a swatch of his hair so thick it was originally thought to be from a bear.
This is the first time the whole genome of an ancient human has been analyzed, and it joins the list of just eight whole genomes of living people that have been decoded so far. It also sheds new light on the…
razib | February 6, 2010A few days ago I discussed a new paper which explores the patterns of natural selection in the genome of the X chromosome. As you know the X is "carried" disproportionately by females, as males have only one copy, so it offers up an interesting window into evolutionary dynamics (see The Red Queen for a popular treatment). Today Dienekes points me to a new paper in Genome Biology which puts the focus on the X chromosome again, Characterization of X-Linked SNP genotypic variation in globally-distributed human populations:
Background
The transmission pattern of the human X chromosome reduces its…
razib | January 26, 2010One of the more substantive consequences of the powerful new genomic techniques has been in the area of ancient DNA extraction and analysis. The Neandertal genome story is arguably the sexiest, but closer to the present day there've been plenty of results which have changed the way we look at the past. The input of genetics has basically demanded a revision of the contemporary consensus of the origins of the Etruscans which emerged from archaeology. Though certainly ancestry and genetic relationship are informative, ancient DNA has also given us windows into the change of function and a…
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 | October 11, 2009About two weeks ago I pointed to the peculiar disjunction between what a paper on Indian genetics actually said, and how people, including some of the researchers who contributed to the paper, were spinning it. For instance, the finding that South Asians can be reasonably modeled as a two-way admixture between "Ancestral North Indians" (ANI) and "Ancestral South Indians" which varies in ratio between between 7:3 and 2:3 across regions & caste groups was translated into "the genetic unity of India." And now I notice in The Guardian another Indian has an article titled Tracing the fissures…
razib | September 15, 2009
One of the problems with human genetics where it resembles economics are the ethical issues involved in experimentation. Luckily for science, but unluckily for individuals, medicine offers many "natural experiments." But in the area of population genetics and history analyses of pedigrees or family based studies centered around particular traits and genes have limitations of scale. Luckily for science again, and unluckily for millions of Amerindians and black Africans, Latin America offers a cornucopia of possibilities when it comes to exploring the outcomes ensuing from admixture between…
razib | September 7, 2009Another study on obesity & Africans, with a slight twist, Admixture Mapping of Obesity-related Traits in African Americans: The Atherosclerosis Risk in Communities (ARIC) Study:
Obesity is an important cause of morbidity and mortality worldwide. In the United States, the prevalence of obesity is higher in African Americans than whites, even after adjustment for socioeconomic status (SES). This leads to the hypothesis that differences in genetic background may contribute to racial/ethnic differences in obesity-related traits. We tested this hypothesis by conducting a genome-wide admixture…
razib | September 5, 2009Singapore is a racially diverse society, so there's a natural pool of diversity from which one can draw for study of human variation. The Han majority of Singapore derive predominantly from Fujian in southeast China. The Indians are mostly from the southern regions dominated by Tamils or Telugus, but there are large minorities from all over the subcontinent. Finally, the Malay category is really an amalgam of peoples of Southeast Asian Muslim origin, from native Singaporean Malays, to Malaysian Malays, to immigrants from Indonesia.
Singapore Genome Variation Project: A haplotype map of three…
razib | September 4, 2009After reading Genetic Discontinuity Between Local Hunter-Gatherers and Central Europe's First Farmers I'm left scratching my head a bit. Cut-out black & white models really benefit from lack of data, and now that there's some serious data I think perhaps that we need to think about starting from a clean slate in many ways. The title of the article is rather justified in the local contexts: on the mitochondrial DNA (female lineage) there is an enormous difference between farming and non-farming populations. Here are the locations of these samples:
The genetic disance seems to have been 5-…
razib | September 3, 2009Genetic Discontinuity Between Local Hunter-Gatherers and Central Europe's First Farmers:
Following the domestication of animals and crops in the Near East some 11,000 years ago, farming reached much of Central Europe by 7,500 years before present. The extent to which these early European farmers were immigrants, or descendants of resident hunter-gatherers who had adopted farming, has been widely debated. We compare new mitochondrial DNA (mtDNA) sequences from late European hunter-gatherer skeletons with those from early farmers, and from modern Europeans. We find large genetic differences…
razib | August 26, 2009There's a new National Geographic special out, The Human Family Tree, which readers might be interested in. Next showing is on the 30th. Seems to be an extension of The Genographic Project.
Clips below the fold:
razib | August 4, 2009Dienekes points me to a new paper, Demographic history of Canary Islands male gene-pool: replacement of native lineages by European (PDF). Here are the results:
Autochthonous (E-M81) and prominent (E-M78 and J-M267) Berber Y-chromosome lineages were detected in the indigenous remains, confirming a North West African origin for their ancestors which confirms previous mitochondrial DNA results. However, in contrast with their female lineages, which have survived in the present-day population since the conquest with only a moderate decline, the male indigenous lineages have dropped constantly…
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…
razib | July 22, 2009
BMC Evolutionary Biology has a new paper which will be up soon (not on site), Reconstructing Indian-Australian phylogenetic link. ScienceDaily has a preview:
Dr Raghavendra Rao worked with a team of researchers from the Anthropological Survey of India to sequence 966 complete mitochondrial DNA genomes from Indian 'relic populations'. He said, "Mitochondrial DNA is inherited only from the mother and so allows us to accurately trace ancestry. We found certain mutations in the DNA sequences of the Indian tribes we sampled that are specific to Australian Aborigines. This shared ancestry suggests…
razib | July 7, 2009In the early 20th century the geographer Halford Mackinder posited that the key to world domination lay in the control of the Eurasian Heartland. This was in sharp contrast to Alfred Mahan's emphasis on the role of naval power. Whatever the applicability of these geopolitical frameworks in the modern era, it is interesting to observe their precedents in the ancient and medieval world. The rise of Rome was facilitated by the Mediterranean essential role as a conduit for communication and trade which connected the cities which were the foci of the Empire. Easy transport of cheap grain from…
razib | May 22, 2009It is well known that different ethnic groups vary when it comes to diseases such as Type II Diabetes. Or, more specifically they vary in terms of risk, all things equal (if you use an online Type II Diabetes calculator you'll see immediately as they sometimes have a parameter for ethnicity). American blacks for example are heavier than American whites. This seems to be true even when you control for socioeconomic status (though as Oprah once said, "You don't need to do a 'study' to figure that out"). There has been research on genetic loci correlating to obesity in European populations…
razib | May 19, 2009400-500 years ago in the midst of the Great Dying somewhere the indigenous inhabitants of the New World suffered mortality rates on the order of 90-95%. This was almost certainly due to the facts of evolutionary history; the indigenous peoples had little defense against Eurasian pathogens. A result has been the reality that most of the New World is inhabited by European, African or mixed populations. But there are exceptions. In Mesoamerica there is still an indigenous dominated region from southern Mexico into the highlands of Guatemala. More substantially the highlands of the Andes, and…