I don't know how many Poalsters know what these graphs mean. PC1 is "primary component #1", the component analyzed that shows the greatest variance between groups. PC2 is "primary component #2", the one with the second largest variance. Note that, in both the cases for canines and for humans, PC2, the vertical graph component, falls right in the middle of the population, which is fairly widely spread. This means that there's one, major component, that sets them apart horizontally. Any further primary components would be even closer together (less variance). So my question is, what is that component? Is it the gene for melanin production? That would make sense. Or is it something more interesting? Does anyone have the data? IMO the vertical component is even more interesting to look at. It appears to correlate with intelligence...