They only apply population stratification from Figure 2 including onwards:
>The results so far do not control for population stratification because we wanted to characterize overall similarity. However, it is important to remember that some of the similarity in genotypes can be explained by simple assortment into relationships with people who have the same ancestral background. The Framingham Heart Study is composed of mostly whites (e.g., of Italian descent), so it is possible that a simple preference for ethnically similar others could explain the results in Fig. 1. However, in the following results, we applied strict controls for population stratification to ensure that any correlation we observed was not due to such a process.
I don't understand why they did not do this for Figure 1 (or why they do not show that figure) - I assume that the difference disappeared, but who knows.
I just realized that this paper is from 2014, first published on arxiv in 2013. I can't find any study replicating it in the 34 citations since so I would be careful (but this type of dataset for replication is hard to come by) https://scholar.google.com.au/scholar?cites=7301900347564089...
>The results so far do not control for population stratification because we wanted to characterize overall similarity. However, it is important to remember that some of the similarity in genotypes can be explained by simple assortment into relationships with people who have the same ancestral background. The Framingham Heart Study is composed of mostly whites (e.g., of Italian descent), so it is possible that a simple preference for ethnically similar others could explain the results in Fig. 1. However, in the following results, we applied strict controls for population stratification to ensure that any correlation we observed was not due to such a process.
I don't understand why they did not do this for Figure 1 (or why they do not show that figure) - I assume that the difference disappeared, but who knows.
I just realized that this paper is from 2014, first published on arxiv in 2013. I can't find any study replicating it in the 34 citations since so I would be careful (but this type of dataset for replication is hard to come by) https://scholar.google.com.au/scholar?cites=7301900347564089...