Thread: Genealogy/History of Mankind

Good afternoon everyone!

There is a sciencey question I have been asking myself for quite a while and I feel you guys might be able to help me!

I'm gonna try to explain my question as clearly as possible and I apologize in advance if it all seems a bit confusing.

It concerns one's direct relatives. Everyone has 2 parents, 4 grand parents, 8 great grand parents and so forth (16,32,64,128,....etc). The thing is, one does not have to look back many generations before the number of direct relatives outnumbers the total population of planet earth!

I know my reasoning is obviously flawed. I was hoping you might be able to tell me what I am missing.

I hope my question is not too idiotic. Thank you for your help!

Med

It isn't idiotic, but it is vague. What are you asking? Are you asking how it is that if you go back far enough, the amount of direct relatives outnumbers the current population?
Well, people die.

Are you asking how it is each person can be related to so many others?
We're all inter-related a little bit. Granted, it's diluted by the many generations between.

Thank you for your reply!

When I talk about the amount of direct relatives (8 great grand parents, 16 great great grand parents,....) I presume that they are from the same generation. Therefore my 64 great great great great grand parent could potentially all be alive during the same period. Following this reasoning, my direct relatives potentially alive at the same time a dozen generations ago outnumbers the total amount of people on earth....

Again, I know I 'm probably missing something very simple

Firstly, there's no reason why they'd be alive at the same time for more than a few years. We had a friend a few years ago whose wife had had a grandfather who fought in the American Civil War. He'd not married until late in life and she was the daughter of his youngest son who also had not married until later in life. Neither of these generations could remember their fathers because they were so young when they died, but it's quite easy for there to be ninety or a hundred+ years between dates of birth of a grandfather and grandchild. And trying to align which generation of my forebears might line up with which generation of hers was a task none of us could be bothered with.

But the really big issue for your question is that we are all much more closely related than you might at first think. 6 degrees of separation doesn't just apply to people we know now.

Originally Posted by Med

Thank you for your reply!

When I talk about the amount of direct relatives (8 great grand parents, 16 great great grand parents,....) I presume that they are from the same generation. Therefore my 64 great great great great grand parent could potentially all be alive during the same period. Following this reasoning, my direct relatives potentially alive at the same time a dozen generations ago outnumbers the total amount of people on earth....

Again, I know I 'm probably missing something very simple

Ah, I see the issue. It's that if you go back far enough, then you presume they should be within the same generation, (alive) and that there would be more people than even in the current population. I understand your dilemma now.
Yes, it is something simple, but very easy to see where it threw you for a loop. It made me do a quick shake of the head when I grasped what you were asking. One of those, "Well, look at that. Never thought of it that way before" moments.

You need to flip that visual cone upside down, is all. Consider that if you have a small population, they will breed- therefore, reproduce.
What you have is close relation at the beginning and it becomes more distant over time. This means that many of those great great however many times grandparents you look at are all the same people! Which is the solution to your dilemma. You were thinking of them as all having to be separate people.

Thank you so much Adelady and Neverfly for your answers! I think I get it. I have many direct great great [....] great grand fathers. but these relatives would also have millions of direct descendants, not just me. I'm sharing them with millions of people and if we look far enough down the family tree (not that far it would seem...) we are all more or less cousins.

Originally Posted by Med

Thank you so much Adelady and Neverfly for your answers! I think I get it. I have many direct great great [....] great grand fathers. but these relatives would also have millions of direct descendants, not just me. I'm sharing them with millions of people and if we look far enough down the family tree (not that far it would seem...) we are all more or less cousins.

Exactly.

Scary, isn't it?
Now- to go all kinds of off topic (talking about how we're all related to eachother in some way) and share this short story. It's a bit silly, but introspective and I enjoyed it.
The Egg

Thank you for sharing this very good short story. I enjoyed it. It does make you think.

Originally Posted by Med

Good afternoon everyone!

There is a sciencey question I have been asking myself for quite a while and I feel you guys might be able to help me!

I'm gonna try to explain my question as clearly as possible and I apologize in advance if it all seems a bit confusing.

It concerns one's direct relatives. Everyone has 2 parents, 4 grand parents, 8 great grand parents and so forth (16,32,64,128,....etc). The thing is, one does not have to look back many generations before the number of direct relatives outnumbers the total population of planet earth!

I know my reasoning is obviously flawed. I was hoping you might be able to tell me what I am missing.

I hope my question is not too idiotic. Thank you for your help!

Med

When you start going back several generations you will find that many of the branches lead to the same persons, so the net count is actually a lot smaller.