"Even when we know the genome intimately, and the pattern of inheritance, and the history of the DNA, and the migration patterns of the people who carried it, and the evolutionary pressures that led to the perpetuation of the genes and phenotypes - even when we know all that, how it manifests can still be mysterious and surprising. Anyone who says differently is selling something." (p.104)
And then it got even more brutal about the random people who make grandiose claims about their ancestors ... because when it comes down to it, you don't have to go back very far before everyone is related to everyone else:
"You are of royal descent, because everyone is. You are of Viking descent, because everyone is. You are of Saracen, Roman, Goth, Hun, Jewish descent, because, well you get the idea. All Europeans are descended from exactly the same people, and not that long ago. Everyone alive in the tenth century who left descendants is the ancestor of every living European today, including Charlemagne, and his children, Drago, Pippin and, of course, not forgetting Hugh. If you're broadly eastern Asian, you're almost certain to have Genghis Kahn sitting atop your tree somewhere in the same manner, as if often claimed. If you're a human being on Earth, you almost certainly have Nefertiti, Confucious or anyone we can actually name from ancient history in your tree, if they left children. The further back you go, the more the certainty of ancestry increases, though the knowledge of our ancestors decreases. It is simultaneously wonderful, trivial, meaningless and fun." (p.152)
Because the study of DNA is mostly interesting and useful on a grand scale, because it is teaching us about the history of the human species rather than the history of any particular person. Because genes are not deterministic, they indicate that something might be the case, or is likely over a population holding a particular gene, not that you will definitely have blue eyes, or die of cancer.
Stay safe. Be kind. Respect your genome.