# Are we all at most 50th cousins? **URL:** \ **Category:** Factual Questions\ **Created:** [September 24, 2012, 12:04am UTC](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637 "2012-09-24T00:04:35Z")\ **Posts on this page:** 20\ **Page:** 5
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [March 5, 2016, 7:40am UTC](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637/81 "2016-03-05T07:40:20Z")
> [@Blake](#): > > How is maintaining a stone age culture in any way evidence of being “so isolated”? Northern Australian Aborigines maintained a stone age culture up to the WWII, and were engaged in annual international trading events. > > The Japanese government is protecting Indian citizens? :dubious: > > Well we know enough to know that you are wrong when you claim they don’t use fire. And we know enough to be highly skeptical of your claims that they don’t wear clothes. And we know enough to know that you are wrong when you claim that: > \*\* > [Finally, on 4 January 1991, Mr Pandit and his colleagues were met on the beach by a party of 28 men, women and children, for once unarmed. ‘They may not have chiefs, but a decision had obviously been taken by the Sentinelese to be friendly towards us,’ Mr Pandit said. ‘We still don’t know how or why.’ > > Now, the anthropologists have learned to remove most of their clothes, watches and spectacles before visiting the Sentinelese and the Jarawa, another isolated tribe. ‘I’ve lost half a dozen pairs of glasses,’ lamented Mr Pandit, who has been stripped naked by the islanders on several occasions. ‘Clothing doesn’t make much sense to them,’ he said. ‘They’re curious about what we’re trying to hide underneath.’]([Islanders running out of isolation: Tim McGirk in the Andaman Islands reports on the fate of the Sentinelese | The Independent | The Independent](http://www.independent.co.uk/news/world/islanders-running-out-of-isolation-tim-mcgirk-in-the-andaman-islands-reports-on-the-fate-of-the-1477566.html)) > \*\* > > An administrative decision was made to stop these visits C2000, but any claim that they are unapproachable is utterly false. They are extremely cautious and prone to hostility, but approachable given time. > > Given your claims that these people do not use fire, do not wear clothes and are totally unapproachable, I suspect that it wouldn’t be too hard to know more than you do. 3 minutes on Google seems to be sufficient. That is an interesting cite **Blake** and I appreciate you sharing it but it didn’t refute much of what I said. All it said was that it took over 20 years for a dedicated group to approach them through persistence. nothing about language and nothing about fire. I made a mistake earlier when I referenced their island as being under Japanese jurisdiction when it is actually Indian (that I correctly referenced earlier). That was simple carelessness on my part. This isn’t a debate and especially not a personal one. I just think it is fascinating that there are isolated tribes of people still left in the world that want to remain that way. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [March 5, 2016, 8:21am UTC](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637/82 "2016-03-05T08:21:22Z")
> [@Shagnasty](#): > > Oh boy, we are reversing position here from our previous debate. No idea what that means. Don’t think I want to. > [@](#): > > The specific claim is that every person on Earth is at least a 50th cousin of everyone else. I say prove it because there are good reasons to think that isn’t true in the case of isolated populations. What are these isolated populations and what are the good reasons. We’ve laready given you our good reasons for believing that it is true. > [@](#): > > If even two people on Earth are isolated by several thousand years of genealogy, they are not within the 50th cousin range. And if even one frog has wings it won’t bump its arse on the ground when it hops. Name these people who could have potentially have been isolated by several thousand years of genealogy? > [@](#): > > Their nearest neighbors are on an island chain in the Indian Ocean. Yes, and the nearest neighbours of Kyushu are on an island chain in the Pacific Ocean. That doesn’t indicate that Okinawans never lived on Hokkaido. What’s point do you think you are making? > [@](#): > > It is huge and means nothing because you gave no evidence that they ever even met or interbred. Well let’s correct that shall we: \*[There is also the story of a Sentineli who grew up among Onge](https://web.archive.org/web/20130402170506id_/andaman.org/BOOK/chapter8/text8.htm#sentineli), best told in the unavoidable Portman’s own words. The story illustrates the degree of uncertainty surrounding things Andamanese even when one of the best-informed authority in the field is involved: ``` The North Sentinel Island was visited on the 15th of February 1895, and I took some Onges over there from the Quince Islands, as I had learnt at their camp there that one of them was a Sentinels, who had, some years before, left the North Sentinel in a canoe and come across, via Rutland Island, to the Quince Islands and the Little Andamans. ``` … ``` From my very slight knowledge of the Onge language, it is quite likely that I misunderstood the supposed Sentinels, and he may either have been driven away from the Sentinel in a storm, possibly as a child, and have been adopted by the Onges when he reached them on the Quince Islands, (the adults with him being killed), or there may really be occasional intercourse either between the Sentinel Jarawa and those on Rutland Island, or between the former and the Onge. It was interesting to note that, unlike their behavior when in the jungles of the Great Andaman, the Onges on each occasion that they have been on the North Sentinel, have taken the lead in searching the forest for Jarawa [=Sentineli], and seemed to have no fear of them.* ``` OK, so now that’s settled. > [@](#): > > Interesting. Explain how the languages of North Sentinel Island and its nearest neighbors are related to each other. Why should I do that? You made the claim that lack of mutual initelligibility is evidence of lack of relationship. I used the example of French and intelligent to show that such a claim is illogical nonsense. Nobody ever claimed that the languages definitely are related (they probably are, we don’t know). I simply demonstrated that your claim that the languages aren’t related because of lack of intelligibility is rubbish. A lack of mutual intelligibility tells us nothing. > [@](#): > > No one including their closest neighbors has any idea what even the most basic rules of their language even consists of. It seems to be completely unrelated to all others. Yet another claim about the Sentinelese that you post as fact, and that is once again untrue. We know approximately nothing about the langugae. It could be very closely related to the other Andaman languages. We simply lack any information either way. \*[The Onge had a name for North Sentinel Island and knew of the island’s existence; they also appear to have recognized some degree of relationship when brought into contact with Sentineli. … A comparison of the languages could perhaps answer this question but with the Sentineli language virtually inaccessible, there is nothing to compare with. The Onge were terrified of the Sentinelis and the frustrated scientists could not even clearly establish from the shouted exchange between Onge and Sentinelis… whether the latter understood at least a little of the formers’ possibly related language.]([https://web.archive.org/web/20130402170506id\_/andaman.org/BOOK/chapter8/text8.htm#sentineli](https://web.archive.org/web/20130402170506id_/andaman.org/BOOK/chapter8/text8.htm#sentineli)) \* And that is approximately everything known about the degree of understanding their closest neighbors have about the language. your claim that their nearest neighbours know nothing is ignorant nonsense. We have absolutely no idea how much their neighbours understand. It could be a lot, it could be nothing. We just don’t know. But whereas actual anthropolgists and linguists acknowledge this, you boldly proclaim certainty that nothing is known. > [@](#): > > I didn’t say ‘use fire’. What the actual fuck? > [@Shagnasty](#): > > they don’t use fire > [@Shagnasty](#): > > **they don’t use fire** > [@Shagnasty](#): > > What I did say was that they didn’t know how to make fire. > [@Shagnasty](#): > > they don’t use fire > [@Shagnasty](#): > > **they don’t use fire** > [@Shagnasty](#): > > **they don’t use fire** > [@](#): > > That is one of the reasons they are so hard to locate. They simply disappear into the foliage when they sense danger and there are no tell-tale signs of smoke to give away their positions. Utter fucking rubbish. \*[The earliest known mention of the Sentineli was published by the British surveyor John Ritchie who wrote down the following observation in 1771: ``` ... and if we may judge from the multitude of lights seen upon the shore at night, it is well inhabited. ``` … . The islanders themselves were seen only by their torches at night or glimpsed as tiny specks on the beach from afar.]([https://web.archive.org/web/20130402170506id\_/andaman.org/BOOK/chapter8/text8.htm#sentineli](https://web.archive.org/web/20130402170506id_/andaman.org/BOOK/chapter8/text8.htm#sentineli))\* [A fire spotted on an island inhabited by the Sentinelese tribe was unconnected to the missing flight,… “But we believe it has nothing to do with the missing Malaysia Airlines plane,” he added, saying that it was possible that the fire was lit by the tribe, who are known to burn thick grassland.](http://www.reuters.com/article/malaysia-airlines-india-idUSL3N0MB4PR20140314) > [@](#): > > [http://mentalfloss.com/article/23973/stone-age-people-north-sentinel-island](http://mentalfloss.com/article/23973/stone-age-people-north-sentinel-island) In what way does this support any of the claims that you have made? It doesn’t mention the people not using fire, in fact exactly the opposite. It doesn’t mention them not making smoke. It doesn’t mention them being hard to see because of a lack of fire. > [@](#): > > This isn’t supposed to be an argument between you and me. No, it’s \*supposed \*to be about presenting facts and fighting ignorance. You have no facts and keep making ignorant statements. > [@](#): > > I find the topic fascinating and I have looked up everything I can on it. And yet you keep making claim after claim that I can refute with references in 3 minute using Google? Let’s see what you have said: 1. They don’t use fire: Proven wrong with your own references. 2. They don’t wear clothes: Proven wrong in 15 seconds with a Google image search. 3. They are unapproachable: Proven wrong in 2 minutes on Google. 4. They don’t make smoke or light with their fires and thus are hard to detect: Proven wrong in 12 seconds on Google. 5. We know that their nearest neighbours don;t understand anyhting of their language. Proven wrong using the previous Google link. No time needed. > [@](#): > > There are plenty of web sites and even some limited Youtube video documentaries from reputable sources that describe what is known about the Sentinalese. It isn’t much but what is known is quite intriguing. It isn’t much, but it all disagrees with what you have posted. It’s quite amazing. We only know about ten things about the Sentinelese, you posted on five of them, and on four you were completely wrong. The only thing you got right is that they use stone age technology. Every other statment you made was wrong. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [March 5, 2016, 8:38am UTC](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637/83 "2016-03-05T08:38:16Z")
> [@Shagnasty](#): > > … they are unapproachable… **Me** Any claim that they are unapproachable is utterly false. Here is reference from a team of anthropologists who approached them many times over many years. > [@Shagnasty](#): > > That is an interesting cite **Blake** and I appreciate you sharing it but it didn’t refute much of what I said. :rolleyes: No, aside from the fact that you said they are unapproachable and my reference documenting multiple intimate approaches, it doesn’t refute much at all. ---
**Author:** ![JohnClay](https://avatars.discourse-cdn.com/v4/letter/j/c37758/32.png) [@JohnClay](https://boards.straightdope.com/u/JohnClay)\ **Post date:** [March 5, 2016, 10:49am UTC](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637/84 "2016-03-05T10:49:13Z")
I’m not sure about the math but perhaps being at most 50th cousins means that for the past 50 generations there are no ancestors in common. So if you go back 50 generations all 50 great-great-great-etc grandparents would be different. That’s 2 ^ 50 g.g.g…grandparents… which is about 10 ^ 16 or 10,000,000,000,000,000 of them that all must be different. ---
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [March 5, 2016, 4:56pm UTC](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637/85 "2016-03-05T16:56:01Z")
Let’s ignore questions of population genetics for this post and just clarify terminology. Are 50th cousins 6 times removed considered to be “50th cousins” for the purpose of OP’s question? Or, would only a 47th cousin 6x removed qualify? (The same consanguinity as 50th cousins with no removal.) I’ll wait for this to be clarified before attempting any detailed guesstimations. Yes, there will be sixth removals and worse necessary in the intriguing difficult question. Other difficulties include estimating permeabilities, the effects of plagues and pogroms, social barriers to interbreeding, etc. Now I’m going to guess that two Han Chinese, chosen at random would probably be 20th-cousins or better, and two Europeans probably 25th cousins or better. How about pick a European at random and a Asian mainlander at random? Wild guess: 99.9% to be 35th cousins or better; 99.99999% chance to be 40th cousins or better; perhaps 100% to be 41st cousin if the criterion excludes extremely remote people. These are wild-ass guesses, and could be off by orders of magnitude. The critical distance, beyond which 99.99999% changes to 100% is definite but unknowable. It could be there is an old monk in Tibet and when he dies, the 100% mark shifts from 43rd cousins to 39th cousin. While an omniscient being would know exactly what that 100% mark lies, the most we can hope for is something like: Picking any two humans on the planet randomly there is a [ul][li] about 0.2% chance they’ll be 15th cousins or better[/li][li] about 5% chance they’ll be 20th cousins or better[/li][li] about 98% chance they’ll be 30th cousins or better[/li][li] about 99.7% chance they’ll be 35th cousins or better[/li][li] almost surely at least 99.999% that they’ll be 45th cousins or better[/li][li] probably at least 99.9999% that they’ll be 45th cousins or better[/li][li] 90% certain that they’ll _always_ be 50th cousins or better[/li][li] 99.9% certain that they’ll always be 55th cousins or better[/li][/ul] I’m NOT saying these vague guesstimates are the correct numbers. The important thing to note is that there are _two_ levels of probability asserted. There certainly is a Nth-cousin relationship which is the closest single-path consanguinity guaranteed between _any_ two living humans. And what that guaranteed N is changes over time. Surely it was once much more than it is now – communication between, say Africa and Australia, was very minimal thousands of years ago. Perhaps N spiked sharply down, some fixed delay after the arrival of Columbus et al in the New World. But whatever N is, we can only guess it. Above I guess there is a 90% chance Colibri is right and 50th-cousinship is guaranteed (but please review the terminology question in the first sentence above). But if I were to write “_It is almost completely certain that the cousin distance is always N or less_” I would agree with Shagnasty and hedge my bets by choosing, say, N = 60. More definitive answers would depend on anthropological facts: how fast do genes diffuse through the Amazon jungle? I’ll guess that even thousands of years ago, slaves were trafficked from one part of that basin to another; no? ---
**Author:** ![UltraVires](https://avatars.discourse-cdn.com/v4/letter/u/ecccb3/32.png) [@UltraVires](https://boards.straightdope.com/u/UltraVires)\ **Post date:** [March 5, 2016, 8:21pm UTC](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637/86 "2016-03-05T20:21:35Z")
I skipped to the end so forgive me if this has been covered, but I remember reading an article that there is a particular point in the past at which every single human on the planet was either: 1) an ancestor to every single person now living, or 2) an ancestor to nobody now living. I recall that that date in the past was no so long ago. And I also remember that if you limit #1 to descendants of a particular ethnic lineage (those of European or African descent) then it is shockingly recent. Does any of this sound familiar or am I way off base? ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [March 5, 2016, 8:29pm UTC](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637/87 "2016-03-05T20:29:52Z")
> [@UltraVires](#): > > I skipped to the end so forgive me if this has been covered, but I remember reading an article that there is a particular point in the past at which every single human on the planet was either: 1) an ancestor to every single person now living, or 2) an ancestor to nobody now living. I recall that that date in the past was no so long ago. > > And I also remember that if you limit #1 to descendants of a particular ethnic lineage (those of European or African descent) then it is shockingly recent. > > Does any of this sound familiar or am I way off base? I’ve heard about 1000 years for Europe. Interestingly, this implies that if somebody tells you they’re descended from William the Conqueror (1028-1087), and you are of European ancestry, you can reasonably say “Well, in all likelihood, I am too”. ---
**Author:** ![UltraVires](https://avatars.discourse-cdn.com/v4/letter/u/ecccb3/32.png) [@UltraVires](https://boards.straightdope.com/u/UltraVires)\ **Post date:** [March 5, 2016, 9:22pm UTC](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637/88 "2016-03-05T21:22:41Z")
> [@yabob](#): > > I’ve heard about 1000 years for Europe. Interestingly, this implies that if somebody tells you they’re descended from William the Conqueror (1028-1087), and you are of European ancestry, you can reasonably say “Well, in all likelihood, I am too”. Right. When I first started genealogy, I was excited that I was descended from William the Conqueror and Charlemagne. It turns out that every white person in the world shares the same lineage. 🙂 ---
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [March 5, 2016, 10:40pm UTC](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637/89 "2016-03-05T22:40:20Z")
> [@UltraVires](#): > > Right. When I first started genealogy, I was excited that I was descended from William the Conqueror and Charlemagne. It turns out that every white person in the world shares the same lineage. 🙂 I have an expert-approved descent from William the Conqueror’s _sister_, who, like William, has a known descent from Charlemagne. However I’ve no approved descent from the Conqueror (though doubtless there are such lines unknown to or unsanctioned by the experts). (Is your descent from the Conqueror expert-approved? Care to post it?) It’s probably true that every Frenchman or Englishman has a (probably unknown) descent from William the Conqueror but I’d be reluctant to extend this confidently to “every white person in the world.” ---
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [March 5, 2016, 10:50pm UTC](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637/90 "2016-03-05T22:50:32Z")
[Here’s a pdf paper](http://people.sc.fsu.edu/~pbeerli/bsc5932/Rohde-et-al.pdf) which uses a computer simulation to guess that the Identical Ancestor Point for all humans is 7400 (4200) years ago, and the MRCA point is 3400 (2000) years ago. (The parenthesized numbers are for liberal mobility.) The conservative estimates correspond to, roughly, 274 generations for IAP and 126 generations for MRCA. (The 51-generation estimate in thread title is for yet another problem.) ---
**Author:** ![aldiboronti](https://avatars.discourse-cdn.com/v4/letter/a/9fc348/32.png) [@aldiboronti](https://boards.straightdope.com/u/aldiboronti)\ **Post date:** [March 8, 2016, 3:00pm UTC](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637/91 "2016-03-08T15:00:10Z")
My son recently had his family tree traced professionally. It turns out my ex-wife and I are descended from two daughters of Edward I, Joan of Acre and Elizabeth, which makes us cousins in whatever degree. The genealogist explained to my son that the royal connection was no big deal as most people of English descent tie in to royalty if you go back 7 or 8 centuries. ---
**Author:** ![wevets](https://avatars.discourse-cdn.com/v4/letter/w/e9a140/32.png) [@wevets](https://boards.straightdope.com/u/wevets)\ **Post date:** [March 8, 2016, 3:41pm UTC](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637/92 "2016-03-08T15:41:18Z")
> [@Shakester](#): > > There are **living** full-blood Australian Aborigines, and while they were never _completely_ isolated from the rest of the world in the way that the Tasmanian sub-group were, they were _mostly_ isolated from everyone except for near neighbours from their arrival in Australia at a very minimum of 40 000 years ago, and most likely 50 to 60 000 years ago. _Mostly_ is the most important word in that paragraph… > [@](#): > > So there’s no way they have have a recent common ancestor with modern European/African/Asian populations. Anyone claiming they do is tripping. There is no way on Earth that they can possibly share an ancestor with modern Europeans any more recently than way over 40 000 years back. This paragraph is nothing but unsupported balderdash… > [@](#): > > We find an ancient association between Australia, New Guinea, and the Mamanwa (a Negrito group from the Philippines), with divergence times for these groups estimated at 36,000 y ago, and supporting the view that these populations represent the descendants of an early “southern route” migration out of Africa, whereas other populations in the region arrived later by a separate dispersal. **We also detect a signal indicative of substantial gene flow between the Indian populations and Australia well before European contact, contrary to the prevailing view that there was no contact between Australia and the rest of the world. We estimate this gene flow to have occurred during the Holocene, 4,230 y ago.** This is also approximately when changes in tool technology, food processing, and the dingo appear in the Australian archaeological record, suggesting that these may be related to the migration from India. [Genome-wide data substantiate Holocene gene flow from India to Australia on JSTOR](https://www.jstor.org/stable/41992121?seq=1#page_scan_tab_contents) (bolding added) ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [March 8, 2016, 7:46pm UTC](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637/93 "2016-03-08T19:46:08Z")
This idea of “Look at these people over there. They’re _so_ far away from everybody else they _have_ to have been genetically isolated for millennia.” needs to be rethought. The two most widely separated people, genetically, are the Hazda of east central Africa and the Koi-San of southwest Africa. Note that these people are on the _same continent_ and have been significantly affected (genetically and linguistically) by the Bantu expansion. So, despite their differences, there has to be some moderate degree of cousin-relatedness. Compared to them, most everybody else: Europeans, Asians, Native Americans, and Native Australians are _much_ more closely related. Cousin-wise, as far as DNA can tell, those are all more closely related than the Hazda to the Koi-San. ---
**Author:** ![JessicaHoyt](https://avatars.discourse-cdn.com/v4/letter/j/e0b2c6/32.png) [@JessicaHoyt](https://boards.straightdope.com/u/JessicaHoyt)\ **Post date:** [June 11, 2016, 3:30am UTC](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637/94 "2016-06-11T03:30:10Z")
What about Native Hawaiians? They seem more cut off from everybody until the late 1700s when it was discovered. There was some contact between Siberia and Alasa even after the land bridge froze (basically until the border was forcibly shut down as the “Ice Curtain” in the 1940s due to thee Cold War) and possibly between Greenland and Iceland. Not sure if there was contact between Indonesia and Australia. However, who would have had contact with Hawaii? Even some sole sailor blown off course would probably not be enough to connect it to the whole gene pool. And I’m sure there are still at least some Native Hawaiians who don’t have mainland ancestry. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [June 11, 2016, 4:52am UTC](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637/95 "2016-06-11T04:52:10Z")
> [@JessicaHoyt](#): > > What about Native Hawaiians? They seem more cut off from everybody until the late 1700s when it was discovered. There was some contact between Siberia and Alasa even after the land bridge froze (basically until the border was forcibly shut down as the “Ice Curtain” in the 1940s due to thee Cold War) and possibly between Greenland and Iceland. Not sure if there was contact between Indonesia and Australia. > > However, who would have had contact with Hawaii? Even some sole sailor blown off course would probably not be enough to connect it to the whole gene pool. And I’m sure there are still at least some Native Hawaiians who don’t have mainland ancestry. Are you planning to resurrect this every few months or years and ask about another isolated population that you just thought of? To recap: the reason that the model prediction for a quite recent genealogical (either parent) MRCA for the entire human population is robust is that an isolated population must remain _absolutely_ isolated in order to seriously violate the assumptions of the model. All it requires for a _single member_ of an isolated population to outbreed. Once you have a genealogy linking any one member of an isolated group to the rest of humanity, then panmictic breeding within the isolated group will rapidly ensure that _everyone_ within that group now has a lineage tracing back to the rest of humanity. So yes, “some sole sailor blown off course” _would_ be enough to connect it to the rest of humanity. And thus the mathematics show that there is no burden of proof to check every last human being. If \*any \* member of a putatively isolated group is related to the rest of humanity, then it is certain that they _all_ are within a fairly small number of generations. ---
**Author:** ![awesome](https://avatars.discourse-cdn.com/v4/letter/a/8baadc/32.png) [@awesome](https://boards.straightdope.com/u/awesome)\ **Post date:** [April 22, 2018, 5:22pm UTC](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637/96 "2018-04-22T17:22:44Z")
Seems like a plausible theory based on Chang’s paper. It may or may not be accurate (not a whole lot of way to know unless you can somehow trace back everybody on earth’s family tree 3000 years) but it’s at least possible. If it’s accurate it’s pretty cool. 5000-10,000 years ago we reach the common ancestors point. Where everybody who was alive is either the ancestor of everybody today or nobody today. These dates will get more and more recent as time goes on. It might take take only 1,500-2,000 years for someone to become the MRCA in the future rather than 3,000. Since we now don’t have to rely on some rare Bering Strait crosser to connect the worldwide family tree. And people also can travel directly from say Ireland to South Africa, rather than having to mate through dozens of intermediary populations between the 2 countries as was the case in the past. ---
**Author:** ![Grim\_Render](https://avatars.discourse-cdn.com/v4/letter/g/a87d85/32.png) [@Grim\_Render](https://boards.straightdope.com/u/Grim_Render)\ **Post date:** [April 22, 2018, 9:40pm UTC](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637/97 "2018-04-22T21:40:03Z")
I don’t know what the odds are than someone could have gotten into the genepool of a small population and then had his genes completely washed out. I suspect it is lower than the odds of becoming a universal ancestor though. It is starting to look like the number of viable Neanderthal-Human hybrids were rather small, and possibly only from a single group/tribe of Neanderthals. Also, the original hybrids seem to have had health issues, including sterility in the male offspring. Further, evolution has selected against Neanderthal genes in us so the percentage of genes in use has been dropping appreciably even in historic times. Yet still we can find Neanderthal genes in every population outside of Africa and some in Africa, billions of people. That seems like a digression, but I think it supports the idea that once someone breeds into a small population, it seems that probability favors some genes staying in the genepool. Now, by our modern perspective, population living close to each other should inbreed unless there are some serious natural barriers between. And not a lot of barriers can stand against the human sex drive. But it appears that this was not such an obvious thing in ancient times. It appeared to be very variable. The techniques for genetic analysis of human remains are getting very good these days, and what we find is that some populations were exchanging genes over large areas. Beijing to the Baltic during the Ice Age. While others stayed completely isolationist. Several of the isolationist populations have gone extinct or eventually merged with other populations of course. But there are still some populations that show no genetic signal of outbreeding for impressive amounts of time. The Kalash seem to have been isolated genetically for about 12 000 years, and some !San for up to 150 000 years. I’ve looked for data on how long the Andamanese may have been isolated, but I have only found estimates for divergence from other groups, which does not really say anything about total isolation. Australian Aborigines appear to have been genetically isolated for about 50 000 years. Previously, there were reports that genetic connections with the Indian subcontinent about 5 000 years back had been found, but research done since this thread was started seems to have disproved that, and shown deep isolation. [Cite](http://www.cell.com/current-biology/pdf/S0960-9822(16)00078-6.pdf). ---
**Author:** ![awesome](https://avatars.discourse-cdn.com/v4/letter/a/8baadc/32.png) [@awesome](https://boards.straightdope.com/u/awesome)\ **Post date:** [April 23, 2018, 1:18am UTC](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637/98 "2018-04-23T01:18:17Z")
> [@Grim\_Render](#): > > I don’t know what the odds are than someone could have gotten into the genepool of a small population and then had his genes completely washed out. > > I suspect it is lower than the odds of becoming a universal ancestor though. It is starting to look like the number of viable Neanderthal-Human hybrids were rather small, and possibly only from a single group/tribe of Neanderthals. Also, the original hybrids seem to have had health issues, including sterility in the male offspring. Further, evolution has selected against Neanderthal genes in us so the percentage of genes in use has been dropping appreciably even in historic times. > > Yet still we can find Neanderthal genes in every population outside of Africa and some in Africa, billions of people. > > That seems like a digression, but I think it supports the idea that once someone breeds into a small population, it seems that probability favors some genes staying in the genepool. > [Cite](http://www.cell.com/current-biology/pdf/S0960-9822(16)00078-6.pdf). After 10 generations there’s only about a 50/50 chance you’ll inherit any genes from a given ancestor. ---
**Author:** ![dropzone](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dropzone/32/7515_2.png) [@dropzone](https://boards.straightdope.com/u/dropzone)\ **Post date:** [April 23, 2018, 5:56am UTC](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637/99 "2018-04-23T05:56:37Z")
I always hated kinship and this antique thread reminds me why. And yet it’s back again ☹ ---
**Author:** ![Grim\_Render](https://avatars.discourse-cdn.com/v4/letter/g/a87d85/32.png) [@Grim\_Render](https://boards.straightdope.com/u/Grim_Render)\ **Post date:** [April 23, 2018, 8:07am UTC](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637/100 "2018-04-23T08:07:52Z")
> [@awesome](#): > > After 10 generations there’s only about a 50/50 chance you’ll inherit any genes from a given ancestor. That seems strange? A quick mental calculation gives an average of 25 after 10 generations, assuming they are not direct male or female line generations. Also, in practice this seems to assume that every generation is with someone unrelated. That the family tree does not fold back upon itself occasionally. In terms of small tribal of clan populations like humans had through most of time, the foldback effect and the chance of genes becoming fixed seems quite high, as the persistence of Neanderthal genes seem to demonstrate. Anyway, for the OP I’d say no. It is enough for one cases to disprove that all of us are 50th cousins or less. Just by statistics, there are 7 billion of us and there is going to be someone somewhere who is an outlier. [Previous page](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637.md?page=4) [Next page](https://boards.straightdope.com/t/are-we-all-at-most-50th-cousins/635637.md?page=6)