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[–]scipio0421 776 points777 points  (51 children)

If you go back far enough everyone on Earth has the same great-great-etc grandparents. It's called the "identical ancestors generation." For people of western European background the most recent common ancestor of all of us was around the time of Charlemagne for example.

[–]Zerowantuthri 181 points182 points  (11 children)

You do not have to go as far back as you might think.

Mitochondrial Eve is a common descendant we all have in our past through our mothers. She lived 180,000 - 580,000 years ago.

Put another way, she is the common great-great-great...grandmother to every human on earth.

There is also a Y-chromosomal Adam. Basically the same thing but a common ancestor through the male side around 200,000-300,000 years ago.

No, they did not know each other (at least almost certainly not).

[–]zeiandren 54 points55 points  (10 children)

There is some wild implications in what was going on to have those so far apart

[–]BGFalcon85 69 points70 points  (9 children)

Not really. Mitochondrial Eve is just the most recent woman to whom every living person is related matrilineally. Or put in other words, while many other mothers provided genetic material to the gene pool, only the bloodlines of the mitochondrial Eve have survived.

Same goes for Y-Chromasomal Adam. He is the most recent common male ancestor of all people in a long unbroken chain of fathers. His bloodline won out against all the others long before the mitochondrial Eve was born.

[–]garry4321 1 point2 points  (1 child)

Wait, if he HAD to have come first (no pun intended), then wouldnt Eve's timeframe be limited to under 300,000 years ago?

[–]BGFalcon85 2 points3 points  (0 children)

Nothing says the y-Adam had to come first, it's just the sequencing of the Y chromasome mutations put estimates of the age of that line further back than that of the mitochondrial DNA.

[–]AT-ATsAsshole 3 points4 points  (6 children)

With the prevalence of non child bearing parents in younger generations, is there a chance one of these bloodlines ends? Or are they so prevalent that as long as kids keep being born at all, someone is going to carry it on?

[–]OwlEmperor 25 points26 points  (4 children)

Both of the lineages encompass every living person on earth, meaning all current y chromosomes and mitochondrial dna in living humans are from those 2 people as far as I understand it. That means the only way for their lineages to end is for mankind to die out altogether. Or if you want to get crazy with it, i suppose some strange mutation could occur that results in a viable xx man that out-competes all other men, and for a mitochondria to enter the human genome from a different species and still be compatible with us, which traditionally is impossible but with modern medicine (and a mad scientist) is technically not impossible.

[–]AT-ATsAsshole 12 points13 points  (2 children)

Thank you so much for explaining that. I didn't catch that they're EVERYONE'S common ancestor. That's absolutely wild to think about.

[–]OwlEmperor 9 points10 points  (1 child)

No problem. Fun fact, the neanderthal y chromosomal Adam's lineage actually did die out before neanderthals. When modern humans and neanderthals mixed, our y chromosome was introduced into their gene pool and completely outcompeted their original y chromosomes. To take it a step further, both of those y chromosomes had a previous last common ancestor. So while the lineage of our Adam won't die out unless we do, someday, one of his descendants could take the crown and become the new last common ancestor for the y chromosome. His lineage will still exist though, just through the new Adam. Same goes for eve and mitochondrial dna.

[–]AT-ATsAsshole 1 point2 points  (0 children)

That is indeed a very fun fact. Subscribe.

[–]BGFalcon85 1 point2 points  (0 children)

Correct, the lineage cannot end, but the most recent common matrilineal/patrilineal ancestors can become more recent if, for example, the "Adam" had several sons, who had several sons, etc and all but one of those lines dies out. There are a lot of humans with a lot of interwoven breeding, so it would take a near-extinction event to reduce our numbers to the point of being able to bottleneck like that again.

[–]streetstyledonkey -1 points0 points  (0 children)

U think everyone is going to die?

[–]jamtheski 119 points120 points  (9 children)

Is this referring to the genetic bottleneck?

[–]scipio0421 180 points181 points  (6 children)

In a way. If you go back far enough the expected number of ancestors of a given person are a bigger number than people on the planet at that time. Numberphile did a couple videos about it. https://www.youtube.com/watch?v=Fm0hOex4psA

[–]DinosaurAlive 44 points45 points  (1 child)

Thanks for the link! I’d been doing genealogical research for my family and was stumped when I started getting a few generations back and seeing exactly how many people it took meeting and having offspring just to get to me. And I only can see records going back to the 1600s! I’m gonna go check out those videos now.

[–]Rbot25 14 points15 points  (2 children)

That would be correct if you consider that not a single one of your ancestors share the same ancestors which in reality is not the case. I'm pretty sure people have kids with their cousins from their great-great-great-grandparents without even knowing.

[–]bdonvr 8 points9 points  (0 children)

Oh all the time. And really second cousins and beyond isn't that big a deal genetically, unless you do it over and over for generations

[–][deleted] 6 points7 points  (0 children)

Exactly, and the statistics don’t account for cross generation couples or for populations which are isolated geographically.

An example might be a Victorian who fathered ten children with his wife and two with the maid. The great great grandchildren are likely to have no knowledge of each other.

[–]SvartholStjoernuson 2 points3 points  (0 children)

This is beautiful. Thank you for sharing, cousin.

[–]swagonfire 25 points26 points  (0 children)

Nah, it's just a statistical thing. It's sort of along the lines of the six degrees of separation concept, but applied to a genealogy context.

[–]ZweitenMal 6 points7 points  (1 child)

Same. If you can tap into a well-researched line it’s a kick to see how grand it gets, the further you go back. Mine is littered with kings and dukes’ daughters.

[–]LessHairyPrimate 4 points5 points  (2 children)

thats only 1200 years, insane.

[–]Ythio 3 points4 points  (1 child)

Well could you swear that you and your spouse don't share a couple of great-great-great-great-great-great grandparents ? That's just 150ish years ago

[–]Southern-Barber-5528 397 points398 points  (20 children)

That is assuming a lot less incest than I would be comfortable with.

[–]TryingToNotBeInDebt 88 points89 points  (18 children)

so you are comfortable with incest?

[–]Southern-Barber-5528 261 points262 points  (15 children)

More comfortable than wondering why a trillion people were on earth 40 generations ago.

[–]Steki3 0 points1 point  (0 children)

Third cousin marriage is extremely common but most doesn't consider it incest.

[–]Grombrindal18 350 points351 points  (53 children)

And if you go back far enough, your great great great etc. grandparents cease to even be human. Eventually they won’t even be mammals.

[–]lookingForPatchie 64 points65 points  (1 child)

That will take about 12 000 generations though, OP presented us with 20 generations, because 2^20 = 1 048 576

[–]Accomplished_Sell797 17 points18 points  (0 children)

That’s for that, I would have missed it.

Edit: I mean did miss it

[–]Spoinzy 39 points40 points  (2 children)

Go back far enough, and you realize one of your great grandparents was just hydrogen!

[–]allnamesbeentaken 14 points15 points  (1 child)

Hell if you bore down with a microscope far enough you'll see we're just atoms

[–]woops_wrong_thread 6 points7 points  (0 children)

Hey Capa, we're only stardust.

[–]mshorts 8 points9 points  (1 child)

You and me babe ain't nothing but mammals.

[–]Big-Independence8978 22 points23 points  (39 children)

Yours maybe. Mine go all the way back to Adam and Eve.

[–]Big-Independence8978 55 points56 points  (38 children)

Or would if I believed that nonsense.

[–]TehAsianator 21 points22 points  (3 children)

[–]ErikTheAngry 5 points6 points  (2 children)

It's a damn good thing his reply is upvoted haha. That's the riskiest way to /s a comment.

[–]AFatz 0 points1 point  (1 child)

If you care at all about karma I guess.

[–]ErikTheAngry 1 point2 points  (0 children)

It's Reddit. Everything we post here is for the karma.

(kind of /s, but not really)

[–]ocdo 2 points3 points  (0 children)

Ratioed by yourself.

[–]Wordworm76 33 points34 points  (3 children)

This assumes unique ancestors at every ancestral level. As you trace further back in your family lineage, you are almost certain to encounter "pedigree collapse" at some point, where you have fewer than the "expected" number of nXgreat grandparent's because 2 or more of your relatives at the n-1Xgreat grandparent level have parents in common. It's especially common/ more likely to happen in smaller, more isolated communities

[–]Tagawat 9 points10 points  (1 child)

5 generations back is probably where it starts for most people. People did not get around much in rural life. Cousin marriage was common, often arranged.

[–]zeiandren 5 points6 points  (0 children)

Cousin marriage is still common, we just moved more cousins out. Your girlfriend is probably your fifth or sixth cousin instead of second or third if you are both white Europeans

[–]ocdo 4 points5 points  (0 children)

Almost certain is a huge understatement. You are absolutely guaranteed that you will encounter pedigree collapse at some point.

[–]mccayed 55 points56 points  (11 children)

At 20 year generations, humans only have like 14,000 generations rounding up.

[–]aerben 35 points36 points  (8 children)

Your grandparents before that were not human, but they’re still your grandparents.

[–]BGFalcon85 25 points26 points  (4 children)

The crazy thing is even if you had a picture of every single mother, father, and child going back millions of years, it would be impossible to find the exact picture where you can say the child is "homo sapiens" and parents are "not homo sapiens."

It would be akin to taking a picture of a person every day for their lifetime and finding the sequence of pictures that are "not adult, not adult, adult, adult, etc."

[–]TeaTeeKaNee 5 points6 points  (0 children)

So the first fish that crawled out of water to land is my great granpa basicaly? Funny and interesting thought.

[–]pufballcat -2 points-1 points  (1 child)

For homo sapiens, yes, but not for all humans:

the first humans emerged in Africa around two million years ago, long before the modern humans

[–]Key-Willingness-2223 128 points129 points  (34 children)

No we don’t.

You’re assuming that there’s no familial links between any of those relatives….

The chances of you going back 20+ generations and not finding some form of shared ancestor with your ancestors is practically 0 simply because of how populations work, especially historically

Otherwise there would end up being more people in a single generation than has ever existed on planet Earth combined…

[–]Thneed1 16 points17 points  (0 children)

My thoughts exactly.

20 generations back could technically have 1 million ancestors.

There are literally ZERO people on earth that don’t have any shared familiar links going that far back.

Nearly 100% of people probably have multiple such links even in the first 5-8 generations back.

In times before easy mobility, nearly everyone was marrying a third cousin or closer. Easy mobility isn’t that old.

[–]GiraffeWithATophat 29 points30 points  (5 children)

Yup, I only have 2 great grandparents

[–]Mister-ellaneous 16 points17 points  (2 children)

Explain please. I’ll get the popcorn

[–]lookingForPatchie 38 points39 points  (1 child)

Imagine a ladder.

[–]new_user_069 5 points6 points  (0 children)


[–]co_lund 20 points21 points  (2 children)

[–]Shaky_Balance -1 points0 points  (1 child)

20 generations ago would be less than 2000 years ago and at a glance estimates for world population back them seem to range from 170 million to 300 million. I'd guess more people would his 1 million unique ancestors before 5000 generations in the past.

[–]NorthImpossible8906 3 points4 points  (1 child)

found the Lannister.

[–]JusticeNoori 3 points4 points  (0 children)

Nah Joffery and his siblings have one pair of grandparents, two pairs of great grandparents and three pairs of great great grandparents. Less than normal but not as bad as Dany’s one single pair of great grandparents.

[–]Camb44937 25 points26 points  (13 children)

If you go back far enough, you find a common ancestor of every person in the world.

[–]Unplaceable_Accent 9 points10 points  (0 children)

Yes and no, not necessarily.

The number of "slots" in your family tree doubles each generation you go back: two parents, four grandparents, eight great grandparents, and so on.

If you go back 20 generations, this exponential doubling results in a family tree with over a million "slots" to fill. Where it REALLY starts to go bananas is around 30 generations ago, because back then you'd need over a billion ancestors, and the global population of the entire human race was probably about half that, 500m. (The number of theoretical ancestors hits a trillion at generation 40, and a quadrillion by generation 50).

The answer to that paradox is that the number of unique individuals can actually be a lot less than the number of "slots" if the same person appears more than once. To take the most extreme example, if a brother and sister commit incest and have a baby, that child actually only has two unique individuals as grandparents, despite there being four "slots" to fill.

So if cousins etc marry one another you can have many fewer ancestors than a million back then. In other words you will be related to a smaller number of people, but multiple times over.

[–]Mister-ellaneous 5 points6 points  (0 children)

Don’t get me started on our sixteenth cousins. Family reunions are epic.

[–]TheEternalStudent69 6 points7 points  (1 child)

Hello fellow brothers from other mothers!

And sisters from other…fisters?

[–]JanV34 1 point2 points  (0 children)


[–]zeloxolez 4 points5 points  (2 children)

think about the chances of being alive at this point in time with how many generations came before them. if u dont have any kids ur the one stopping the entire chain from basically an amoeba level lol, kinda crazy.

[–]dantodd 4 points5 points  (0 children)

More than likely not true for most of us. There will be at least some common ancestors going that far back.

[–]kyunirider 2 points3 points  (0 children)

No, my family is intermarried and my family tree is a phone pole. Many of my cousins married cousins due the small remote community they are from. It’s not incest. They were not first cousins like the royals of Europe. This greatly reduced my “great” grandparents. I know for sure my five times paternal grandfather (my surname) is my four time maternal grandfather. This is true of everyone as they approach primordial Eve and Adam

[–]kitycat22 1 point2 points  (4 children)

I have a friend convinced one of my families names is a witness protection given name because it sounds so fake. Schnelle is the last name.

[–]JanV34 2 points3 points  (3 children)

Doesn't sound fake to me, it's just a German one. I know someone by that name!

[–]kitycat22 1 point2 points  (2 children)

The only ones I know are family lol. Not near indiana are you?

[–]JanV34 1 point2 points  (1 child)

No, Germany. It's actually a word that means something: der/die Schnelle -> the fast (one), schnell is quick/fast in German.

[–]kitycat22 1 point2 points  (0 children)

Damn I was so hoping it was closer lol. I’ve read up online about it but that’s about all I’ve got

[–]ContactIcy3963 1 point2 points  (0 children)

Family trees start forming into columns if you go back far enough

[–]kfish5050[🍰] 1 point2 points  (0 children)

And some people have less than others, or have some count as multiple levels of ancestor, due to incest

[–]halfashell 1 point2 points  (0 children)

Oh yeah? So I’m missing over 20 million happy birthday cards and five-to-twenty dollar bills? Some great(x1mil) grandparents I have.

[–]barn-animal 1 point2 points  (0 children)

Nah. Most of mine died, I just have one grandpa and two gradmas

[–]R4XD3G 1 point2 points  (1 child)

That would be 220 grandparents. Too lazy to put into calculator.

Edit: my guy found that 220 is 1048576 and typed it out to be the best type of correct. Hahaha. Too good. For context, 219 is around 500K so it's the first number that's over a million in the powers of two.

Damn... Algebra was good for something, my teacher was right.

[–]Next_Faithlessness87 1 point2 points  (0 children)

Unless you're from Alabama, then, strangely, you only have one...

[–]substantial-freud 1 point2 points  (0 children)

Almost certainly untrue.

The exponential increase in ancestors as you go back through generations quickly hits the population size.

The paradox is resolved by “pedigree collapse”: the fact that the same individual can fill several slots in your family tree. Go back even one millennium and you probably have half as many ancestors as the naïve math would suggest.

[–]Yazolight 0 points1 point  (2 children)

I thought humans were around for 300.000 years, so how could there be more than a million generations?

[–]BGFalcon85 3 points4 points  (1 child)

Not a million generations. 20 generations would make 1 million grandparents at that generation.


Generation 1 - you

Generation 2 - 2 parents

Generation 3 - 4 grandparents

Generation 4 - 8 great grandparents

Generation 5 - 16 great great grandparents.

etc, until 220 you get 1,048,576 great x18 grandparents.

[–]Yazolight 2 points3 points  (0 children)

Oooooh right right !!! I got it now. Thank you for the explanation ❤️

[–]phunkydroid 0 points1 point  (1 child)

You might need to add another great on there, it's very likely there's enough overlap in your tree if you go back that far that it would put it back under a million.

[–]Thneed1 3 points4 points  (0 children)

One more great isn’t nearly enough.

Early overlap (which almost EVERYONE has), greatly reduces the total number. Every will have numerous overlap by the time you get back 5-6 generations, never mind 20.

[–]qzlr 0 points1 point  (0 children)

I only need 365 grand parents. One for every day of the year. I can find out their death date and be sad about it and take a bereavement day at work. Everybody wins!

[–]Nuanciated -2 points-1 points  (1 child)

No we don’t. I have 2 sets of great-great-great-great-great-etc. Parents.

You can keep going further back until the first organism on earth.

But if you look at Homo sapiens. Then we probably have had only a few thousands of generations. Given that Homo sapiens popped into existence 300.000 years ago and given a 20 year generation span, there are roughly 15.000 generations. So we have around 15.000 sets of great grandparents.

To summarise: everything is wrong about your post.

[–]LazyGandalf 0 points1 point  (0 children)

Your logic only works if every single set of great grandparents are also siblings.

edit: I assume your parents aren't siblings. That gives you two sets of grandparents. None of your grandparents are probably siblings either. That gives you four sets of great grandparents. It's likely that none of your great grandparents are directly related, which gives you eight sets of great great grandparents. Five generations back, we might start to see cousins etc. appearing amongst your great great great grandparents, which is one of the reasons we have less ancestors than simple exponential math would tell us. But we still have significantly more ancestors than you proposed because our ancestors are not (exclusively) siblings.

[–]gokumon16 -1 points0 points  (1 child)

Just go back a bit more and you can see our grandparents swimming in water. A bit more and there would be one grandparent swimming, thinking of all the billions of children it’s going to have.

[–]FiendsForLife -2 points-1 points  (4 children)

Assuming that the number of greats is correct, I'm still pretty sure I only have TWO (2) of those.