Here is another puzzle. Can you guess what this figure is depicting?
Guess: What genes you get from which ancestor?
Yes! What are the black lines on the edges?
How much that 10th generation ancestor contributes to the overall genome of the person in the middle?
Where the genes of the central genome come from of the 10th generation ancestors?
Ancestors that contribute no DNA to the descendant.
Bingo. The black segments along the circumference are genetic ghosts: Genealogical ancestors that pass the center descendant no DNA.
Okay, I get it. Conversely, if I look for white spots, those are whose genes get through?
White ancestors are really just very light gray. They pass on a tiny amount if DNA to the individual. Usually the darker ancestors are passing more, but the genetic ghosts are highlighted in black for visibility.
This is really informative. And it is only 10 generations back (about 200 years). So for our ancestors thousands or tens of thousands of years back, they contributed essential nothing to our individual genome?
That’s right. Though interbreeding increases it some, and we can see more of we look at our whole current population. However the basic story is the same. The vast majority of our ancestors pass us no DNA.
Also related to pedigree collapse or pedigree extinction!
Wait… let me guess, but let me imagine I’ve not read this entire thread.
It is a sunset in Hong Kong as seen upside-down through a peep-hole in a door.
Am I right?
But the DNA we get from five generations back is received from five generations back and so on, and so on. So isn’t the overall effect different than what is described here? Isn’t there some compounding that is accumulated that really makes the numbers different?
The math that matters is that living creatures, on average, dont move very far from their ancestral territories. So within 5 or 6 generations Pedigree Collapse begins when cousins unwittingly mate with cousins.
Mathematically speaking, Emperor Charlemagne (circa 800 CE) could have 1 billion descendants by the year 1800. But what if Europe’s population is 800 million by that time? Where did 200 million possible descendants disappear to? They disappeared in the unions of cousins who merged dozens of mutual ancestries into a mere thread… instead of a barrel of anceatral ropes.
And… virtually everyone is a descendant of an Emperor!