So… lately, I’ve been hopelessly addicted to ancestry.com (INTERVENTION TIME PLEASE!!), and I researched my adopted sister’s family tree. I found that she is a direct 22nd generation descendant of Robert the Bruce, who founded Scotland in the early 14th century, yay. We were trying to figure out how many 22nd generation descendants there might be, and I’m not sure what the answer is. Most of the resources I found seem to assume that ALL descendants are included (cousins of cousins of cousins of cousins of… you get the idea.That’s how we’re all related.) But that’s really not the question. How many DIRECT descendants would there be by now? (Robert the Bruce is my sister Emma’s direct great-great-great-great-great… etc etc etc, grandfather. Not the cousin of the aunt of the uncle of the nth cousin of the… you see what I mean.) Does anyone know how to figure out the theoretical number of direct descendants only?
It just seems that the information I’ve found about how to count potential descendants is assuming that nth cousins are all included in the list. Probably a good chunk of all the people on the planet today are nth to the nth cousins of Robert the Bruce, but that isn’t the same as direct descendants.
For example, I found a first cousin four times removed on ancestry.com, but that isn’t at ALL the same as a fourth cousin.We shared a great-great-great grandpa.Finding a fourth cousin would be fun too, but we would not be anywhere near as closely related.
There’s no real way to tell. If Robert had had two children and each of those had had two children then there would be 2[sup]22[/sup] = 4,194,304 direct descendants in the 22nd generation and 8,388,606 in all generations through the 22nd.
However, it’s likely there were more than 2 children in each generation. If there were 3 children in each generation there would be 3[sup]22[/sup] > 30 billion descendants in the 22nd generation. This, of course, is impossible as there aren’t that many people on earth.
Even if there were only 2 children in each generation, and all lived to reproduce at least 2 children, etc., you’d eventually have n[sup]th[/sup] cousins marrying so that the numbers don’t grow nearly that fast. This is easier to visualize in the opposite direction. How many ancestors do you or your sister have 22 generations back? It’s the same answer, 2[sup]22[/sup] = 4,194,304 direct. How about 30 generations back? That’s approximately 1 billion which was more than the population of the world that far back.
But a reasonable guess is that Robert has something like tens to perhaps hundreds of millions direct descendants living now, I’d think.
Well, there were quite a few places where the family tree didn’t fork… A lot of cousins marrying cousins. I can’t talk, though, because in MY family tree, it isn’t necessary to go nearly as far back as you would think (and hope) before finding the non-forking phenomenon. But I couldn’t find any connection to Robert Bruce for me, anyway. :rolleyes:
Half of my ancestors were in the same exact part of Sweden forever and ever and ever, apparently, and certainly before 1314. Most of the other half did the same thing in a small part of Germany. The rest were in England and stayed in yet another small place that was nowhere near Scotland. So it’s hard to see how I could be directly related to anyone who was alive in Scotland then. I could have *nth *cousins, but it’s very unlikely that I have first cousins once removed. Do you see what I mean? An awful lot of people have ancestors who just stayed exactly where they were until they finally picked up and emigrated to America at some point. THEN, they stayed in the new place they’d moved to and married people who were already there, all of whom also came from a small place where they’d all lived forever.That’s what all of mine did. After my direct ancestors got here, they were basically ALL in either Otter Tail County, MN or Person County, N.C. until relatively very recently. I don’t think they would have had a chance to mix far enough back to create tons of direct descendants today.
ETA: I could have first/second/third/fourth/etc etc etc cousins from a common ancestor, but it’s very unlikely that I have anywhere remotely as many FIRST cousins one/two/three/etc etc etc times removed. Almost every single one of my ancestors just stayed in the same place for way too long, and they started doing it way too early.
I’m an amateur genealogist, and this is a question which has intrigued me. But the answers are far from clear. Most of the published estimates are based on models, but the modeling is non-trivial. (What are the parameters of inter-class marriage? Plagues tend to be concentrated geographically, etc.)
For example, I think Americans might have more 6th cousins on average than Europeans do, due to higher mobility and high population growth in frontier areas.
Cite, please? (I’m not saying this is wrong – though I’m doubtful – but would like to see the claim.) I do know that many Englishmen have John of Gaunt as their link to most recent King.
(And BTW, what did you mean by “one way or another” ?)
Everyone is nth cousin nth removed of each other (and n is smaller than you’d think). Direct descendants means … direct descendants – no nephews or cousins allowed, even 1st cousins. I assume jezzaOZ meant direct descendants (though he chose to muddy the waters with “one way or another.”)
@ OldGuy – Assuming two children on average, and 2[sup]K[/sup] after K generations doesn’t work out too well. Calculating that way leads to the conclusion that Charlemagne has trillions of living descendants. Even those of us who agree it is certain that 99.9% of those with European ancestry are descended from Charlemagne think that “trillions” is an overestimate.
I agree about the problems with theoretical models, for sure. How many realistic factors do they actually take into account? For instance, here’s what happened in my family…
Picture Varmland, Sweden in about the 9th century, if not earlier.
Branch #1: (looking around) This is nice. Let’s stay here forever and eat lutefisk casserole.
And they did, until 1880…
(arriving in Otter Tail County, Minnesota in about 1880)
Let’s stay here and never ever marry anyone who isn’t from here.
(Most of them are still there.)
Then picture this exact scenario with Branch #2, but in Pommern, Cochem-Zell, Rheinland-Pfalz, Germany. (and yes, they came to Otter Tail County, Minnesota too. And most of THEM are still there.)
And the Brooks group, which came to Virginia in 1635 and all moved to Person County, VA ASAP. (yes, I know, it wasn’t called that at the time…
There were a few exceptions to this, but they were rare exceptions and usually involved marrying someone who lived in the next county.
This is a little extreme-- which is why I’m just a walking recessive gene-- but I think there’s more truth to it than is generally realized when putting the models together. Most people used to basically stay in the same place and not marry outside of that place. (And I’m STILL getting my sister a Stuart T-shirt. She’s a direct descendant, no cousins involved!
A lot of cousins marrying cousins. I can’t talk, though, because in MY family tree, it isn’t necessary to go nearly as far back as you would think (and hope) before finding the non-forking phenomenon. But I couldn’t find any connection to Robert Bruce for me, anyway. :rolleyes:
