DNA Results

I recently received results from 23andMe, a company that genotypes DNA sequences, including information on my Y-chromosome and mitochondrial haplogroups, and the geographic composition of my autosomal DNA.  My Y-chromosome haplogroup is R1b1b2a1a2f, and is densest in the northern portion of Ireland.  This makes sense, given that my great-great-grandfather (patriline), Clarence O'Hagan, was born in Ireland in the mid-19th century.  My mitochondrial haplogroup, somewhat more surprisingly, is A2, one of the four major unique founder haplogroups of the Americas (along with B2, C1, and D1).  This means that my matriline, which I have reliably traced back to one Josefa Villanazul (who was born in the first half of the 18th century and gave birth to a daughter c1745 in Villa de Sinaloa, Sinaloa, Mexico), originates in the Americas, and not Europe.

It has long been known that the Americas were peopled by humans from Asia, but there has been significant disagreement as to when.  Recent work (Tamm et al. 2007) has suggested that humans reached Beringia, the former region between Siberia and Alaska, before the peak of the last ice age (by 30,000 before the present), but that they did not expand into the Americas until ~15,000 years later.  The reasoning behind this proposal is that none of the four founder haplogroups of the Americas is found in Asia, and that each of them is found equally distributed throughout the Americas.  This suggests that a lengthy period of genetic isolation must have occurred in Beringia, followed by a period of rapid expansion.  If a period of isolation in Beringia did not occur, one would not expect to find the degree of genetic uniqueness that is found in the Americas; and if expansion into the Americas had not been rapid, then one would not expect to find the equal distribution that is in fact attested.

23andMe reports the geographic distribution of autosomal DNA relative to 31 populations worldwide, with three different confidence levels: "Speculative" (51%), "Standard" (75%) and "Conservative" (95%).  These confidence levels differ by how much DNA is assigned to one of these 31 populations, and by whether various percentages are assigned to larger or smaller regions.  One can get a sense of this by comparing the standard and conservative composition reports.

Ancestry Composition, Standard

In the standard composition, 9.9% of my DNA is unassigned, but 78.7% is European, 9.8% is East Asian & Native American, 1.6% is Sub-Saharan African, and 0.1% is Middle Eastern & North African.  These are fairly coarse-grained categories, but can in most cases be specified further.  For example, of the 9.8% that is East Asian & Native American, 6.1% can be assigned to the Americas themselves, while 3.7% cannot, i.e., the latter must be assigned at the level of East Asia and the Americas.  Similarly, 25.8% of the 78.7% European DNA cannot be specified further, while 9.8% and 5.3% is British/Irish and Iberian, respectively.  (In contrast, 9.2% of my father Wade's DNA can be assigned to the Americas, while 5.0% and 6.0% is British/Irish and Iberian, respectively.)

Ancestry Composition, Conservative

In the conservative composition, 25.2% of my DNA is unassigned, but 68.8% is European, 5.9% is East Asian & Native American, and 0.1% is Sub-Saharan African.  Unlike the standard composition, only 1.7% of the East Asian & Native American DNA can be assigned to the Americas (as opposed to my father's 2.7%), a whopping 53.3% must be assigned to Europe as a whole, and Britain/Ireland and Iberia disappear as specific regions altogether.