In 2008 Ethnicity Struck Back, but in 2009, it already seems
we're well on our way to finding the structure within ethnic
groups themselves, as was possible in Sardinia and Estonia. A
new paper shows that such structure exists in Iceland, a
population often used for association studies, because of its
presumed homogeneity. Individuals with most of their ancestry
from one of several regions tend to cluster together in the PCA
plot (top), but "random" individuals with ancestry from many
regions tend to be all over the map. From the paper: The
ancestry predictions were correct for 47% of samples, correct to
within a distance of one region for 74% of samples, and correct
to within a distance of two regions for 93% of samples. The
accuracy increased to 58% (87% to within one region, 97% to
within two regions) when restricting to the 98 (of 250) samples
with at least 16 of 32 ancestors from a single region.Figure 3
shows the Icelandic populations in the context of Scotland and
Norway. From the paper: Based on the a