> Why it is relevant is beyond me.
Perhaps the irony escapes you.
None of my ancestors owned slaves ... at least for the past 1000 years. They were poor serfs and lived under oppression as far back as we can look.
You do not and cannot know that. (Neither can I or anyone else.)
Nobles and landlords, not to mention invading or just passing through soldiers generally made their best effort to be the "fathers of their country," and to a very considerable extent they were.
Recent DNA evidence has shown we are on average descended from only half as many male ancestors as female ancestors. Which means the upper crust oppressive bastards were a great deal more likely to pass on their genes than the oppressed men were.
Probably a good thing, as the oppressive bastards were probably on average more genetically fit and dispersion of their genes down into the general population was generally positive. (From a genetic standpoint, not that of the oppressed men and women.)
Brief mathematical analysis.
Allowing for three generations per century, 1000 years ago each of us would have had 2 to 30th power ancestors.
Or 1,073,741,824. This is obviously inaccurate, as there weren't anywhere near that many people around at the time. And of course there was a lot of "overlap," with the same ancestors found in multiple lines.
But it is still pretty much a fact that if we go back far enough each of us is probably descended from just about everybody alive in that area at the time, those who left descendants. Statistically speaking. And as stated, the slaving, oppressing bastards were a lot more likely to reproduce than the oppressed men.
As Mel Brooks said, "It is good to be the King!"