# Geneologists and geneticists: How closely related are all humans? **URL:** \ **Category:** Factual Questions\ **Created:** [July 20, 2006, 3:33pm UTC](https://boards.straightdope.com/t/geneologists-and-geneticists-how-closely-related-are-all-humans/365346 "2006-07-20T15:33:21Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![Valteron](https://avatars.discourse-cdn.com/v4/letter/v/f17d59/32.png) [@Valteron](https://boards.straightdope.com/u/Valteron)\ **Post date:** [July 20, 2006, 3:33pm UTC](https://boards.straightdope.com/t/geneologists-and-geneticists-how-closely-related-are-all-humans/365346/1 "2006-07-20T15:33:21Z")
IANAS (The S is for scientist) but I have read all kinds of things that lead me to conclude that I am far more closely related to ALL other humans (even black and asian) than the average person (and certainly the average racist) would suspect. There seems to be a number of reasons for this: What I am sayting 1. The “going forwards” hypothesis":Human beings of all races are so genetically similar (and virtually identical under the skin) that many scientists postulate that the whole human race is descended from a very small group of a few dozen early creatures that survived some near extinction. Most species display much more variation than we do. While a blue-black seven-foot Watusi and a flaxen-blond Swedish girl may strike you as very different, I have read that they are far less different than different breeds of cats, for example. 2. The “going backwards” hypothesis: Most of us say we are “pure Irish” or “pure French” or “pure white” or “pure Chinese” by tracing through the male line on our family tree. But from a genetic point of view this is very misleading and artificial. I am the child of two people (not just my father), who were the children of four people (my granparents), who were the children of eight people, etc. Now then, counting for or five generations per century (people used to have children a lot younger than now) thirty generations of my ancestors takes me back to about the 12th to 14th centuries. But doubling my ancestors thirty times gives me a number in the BILLIONS!!! There were not billions of people on Earth at any time before the last century or so, right? And that is just ME! What about you, gentle readers? If each of you is descended from billions of people, and there are about 6 billion people on Earth right now. . . .well do the math! The only answer to this is that my family tree and yours are not trees at all. The idea that you and I have distinct “trees” of ancestry is absurd. You would have to do a giganic family “bush” for the whole humn race at once. If you are going to trace your ancestry through both your father and mother, then you would be shown as a dot with your name next to it representing one person at the top of the page. So would every other human being on earth. Now then, two lines would lead down from my dot to two dots identified as with mother and father’s names. And then two lines from each of them to my four grandparents, and so on. So, in tracing back my ancestry, I would at each ancestor have the choice of following the male or female line to the next ancestor. As I understand it, two things would occur. I would start to notice after a couple of centuries that the same persons keep coming up as my ancestors in different roles depending on what lines you follow to reach them. And secondly, we would discover that you and I and every other human being on Earth have literally hundreds and even thousands of common ancestors. THAT is why there were not billions of people on Eath in the 12th century! I would be pleased if any scientists or genetics experts out there could tell me if any of this is right or am I just spoouting bullshit? ---
**Author:** ![Bricker](https://avatars.discourse-cdn.com/v4/letter/b/977dab/32.png) [@Bricker](https://boards.straightdope.com/u/Bricker)\ **Post date:** [July 20, 2006, 3:47pm UTC](https://boards.straightdope.com/t/geneologists-and-geneticists-how-closely-related-are-all-humans/365346/2 "2006-07-20T15:47:47Z")
> [@Valteron](#): > > And that is just ME! What about you, gentle readers? If each of you is descended from billions of people, and there are about 6 billion people on Earth right now. . . .well do the math! Well, as a [Very Wise Commentator](http://www.straightdope.com/classics/a2_083b.html) pointed out: > [@](#): > > The ancestor puzzle has its explanation in what one genealogist has called “pedigree collapse.” This occurs when relatives, usually cousins, marry, in effect narrowing the family tree. (Fortunately for the gene pool, most of the cousins are only distantly related.) When this happens you find that many of the “slots” in a given generation of your family tree are filled by duplicates. > > Consider an extreme case. Mr. and Mrs. Nosepicker have two children, a girl and a boy. These two develop an unnatural yen for one another and marry. Six months later the girl gives birth to an eight-pound horseradish with a lisp. In theory, the horseradish has four grandparents. In reality, its maternal and paternal grandparents are identical. Two of the four grandparent slots are thus filled by duplicates–pedigree collapse with a vengeance. Only slightly less extreme is the case of Alfonso XIII of Spain (1886-1941). Because of inbreeding in the royal family, he had only ten great-great-grandparents instead of the expected 16. > > If you go back far enough, however, pedigree collapse happens to everybody. Think of your personal family tree as a diamond-shaped array imposed on the ever-spreading fan of human generations. (I told you this was cosmic.) As you trace your pedigree back, the number of ancestors in each generation increases steadily up to a point, then slows, stops, and finally collapses. Go back far enough and no doubt you would find that you and all your ancestors were descended from the first human tribe in some remote Mesopotamian village. Or, if you like, from Adam and Eve in the Garden of Eden. > > These simple facts have given rise to some remarkable displays of statistical pyrotechnics. Demographer Kenneth Wachtel estimates that the typical English child born in 1947 would have had around 60,000 theoretical ancestors at the time of the discovery of America. Of this number, 95 percent would have been different individuals and 5 percent duplicates. (Sounds like Invasion of the Body Snatchers, but you know what I mean.) Twenty generations back the kid would have 600,000 ancestors, one-third of which would be duplicates. At the time of the Black Death, he’d have had 3.5 million–30 percent real, 70 percent duplicates. The maximum number of “real” ancestors occurs around 1200 AD–2 million, some 80 percent of the population of England. > > Pedigree collapse explains why it’s so easy for professional genealogists to trace your lineage back to royalty–go far enough back and you’re related to everybody. For that matter, you’re probably related to everybody alive today. Some geneticists believe that everybody on earth is at least 50th cousin to everybody else. For a fuller discussion of the above, see The Mountain of Names, by Alex Shoumatoff (1985). ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [July 20, 2006, 4:48pm UTC](https://boards.straightdope.com/t/geneologists-and-geneticists-how-closely-related-are-all-humans/365346/3 "2006-07-20T16:48:45Z")
According to an [article](http://www.economist.com/surveys/displaystory.cfm?story_id=5299209) published in The Economist (subscription required), we all seem to have a common female human ancestor: > [@](#): > > In 1987, Rebecca Cann, one of Wilson’s students, applied his insight to a series of specimens taken from people whose ancestors came from different parts of the world. By analysing the mutational differences that had accumulated since their mitochondria shared a common ancestor, she was able to construct a matriline (or, perhaps more accurately, a matritree) connecting them. > > The result was a revelation. Whichever way you drew the tree (statistics not being an exact science, there was more than one solution), its root was in Africa. Homo sapiens was thus unveiled as an African species. But Dr Cann went further. Using estimates of how often mutations appear in mitochondrial DNA (the so-called molecular clock), she and Wilson did some matridendrochronology. The result suggests that all the lines converge on the ovaries of a single woman who lived some 150,000 years ago. And furthermore, all men alive today have a common male ancestor: > [@](#): > > And you can now do a similar trick for the patriline using part of the male (Y) chromosome in the cell nucleus, because this passes only from father to son. Unfortunately for romantics, the most recent common ancestor of the Y-chromosome is a lot more recent than its mitochondrial equivalent. African Adam was born 60,000-90,000 years ago, and so could not have met African Eve. ---
**Author:** ![Zeldar](https://avatars.discourse-cdn.com/v4/letter/z/b77776/32.png) [@Zeldar](https://boards.straightdope.com/u/Zeldar)\ **Post date:** [July 20, 2006, 5:16pm UTC](https://boards.straightdope.com/t/geneologists-and-geneticists-how-closely-related-are-all-humans/365346/4 "2006-07-20T17:16:04Z")
Another angle to approach this subject from relates to the small town syndrome. Before the current 100-year period (let’s go back to 1900 arbitrarily) it was uncommon for families to uproot and move to a distant locale. Small towns and villages kept pretty much the same basic families, even when the newer generations moved to the “outskirts” or to a nearby community. In regions as isolated as the Appalachians (as a for instance) there might be only a dozen or so families in a sizeable geographic area. After a few generations the uniqueness of any given family would be hard to maintain. Intermarriage would make most of the people in that community kin to each other, often in several ways. I spent my early years in a small town. There were hundreds of families, but many people I knew were kin to many others in town and knew that relationship. Some were “third cousins” or more, but the closeness of kinship was a fact of life, and a frequent topic of conversation. My wife comes from a similar situation and knows her kinship to many of the people in her school class and her playmates. Some of them are kin in several ways. A running gag is, “I’m kin to myself three different ways.” Extend this phenomenon to larger cities, to counties, to states, and even to countries, and the same basic idea applies. [hijack] Not on topic as such, but similar: how many molecules of air that you’re breathing now were also breathed by William Shakespeare or Genghis Khan or John Wilkes Booth? [/hijack] ---
**Author:** ![Valteron](https://avatars.discourse-cdn.com/v4/letter/v/f17d59/32.png) [@Valteron](https://boards.straightdope.com/u/Valteron)\ **Post date:** [July 20, 2006, 6:52pm UTC](https://boards.straightdope.com/t/geneologists-and-geneticists-how-closely-related-are-all-humans/365346/5 "2006-07-20T18:52:17Z")
> [@Zeldar](#): > > [hijack] Not on topic as such, but similar: how many molecules of air that you’re breathing now were also breathed by William Shakespeare or Genghis Khan or John Wilkes Booth? [/hijack] Not to hijack my own thread, but dear Zeldar, you bring up some interesting points. As long as we are talking about the use and reuse of xygen molecules in the oxygen-carbon cycle, what about the water cycle? The water we sweat/piss out eventually becomes part of rivers oceans, etc. and eventually evaporates and falls back down as rain. So even if your Evian or Perrier is absolutely fresh, you have no complete assurance it was not part of someone’s piss in the past. Think about all the funny possibilities. A molecule of H2O in the Pope’s Communion wine was once pissed out by Martin Luther in 1520. A molecule in the Chief Rabbi’s Passover wine once flowed through Hitler’s uncircumcised dick. George Bush has a molecule from Osama Bin Laden in his dinner water tonight. Since dinosaurs existed for hundreds of millions of years (meaning billions upon tens of billions of individual animals) and since some of those lads had a bladder the size of a Volkswagen, it is almost CERTAIN, I would think, that we have ingested a water molecule once pissed out by a dinosaur. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [July 20, 2006, 7:01pm UTC](https://boards.straightdope.com/t/geneologists-and-geneticists-how-closely-related-are-all-humans/365346/6 "2006-07-20T19:01:29Z")
It’s hypothesized that humans went thru a few [Population Bottlenecks](http://www.bookrags.com/sciences/genetics/population-bottleneck-gen-03.html), although I think “a few dozen” would be overatating the narrowness of the most recent one. Humans are indeed quite similar,genetically, although I don’t know why domestic cats should be any standard to compare us to. If we assume that they are all decended from one domestication event, then they’re probably more closely related to each to each other than we are. The site I linked to compares us to our close relatives, chimps, and you can see how much less genetiic diversity we have than they do. ---
**Author:** ![Valteron](https://avatars.discourse-cdn.com/v4/letter/v/f17d59/32.png) [@Valteron](https://boards.straightdope.com/u/Valteron)\ **Post date:** [July 20, 2006, 7:19pm UTC](https://boards.straightdope.com/t/geneologists-and-geneticists-how-closely-related-are-all-humans/365346/7 "2006-07-20T19:19:14Z")
Seriously, then, how likely is it that say, a Nazi or a KKK or Aryan Front member has a black person, a semite (Jewsish or Arab) or an asiatic or Amerindian somewhere in their geneology if you go back through ALL their ancestors, following the male and female lines and all granparents, etc.? Say if you go back 100 generations, which would be about 2,500 years, or about the time of Alexander the Great? How likely is it? ---
**Author:** ![UncleRojelio](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/unclerojelio/32/3160_2.png) [@UncleRojelio](https://boards.straightdope.com/u/UncleRojelio)\ **Post date:** [July 20, 2006, 7:24pm UTC](https://boards.straightdope.com/t/geneologists-and-geneticists-how-closely-related-are-all-humans/365346/8 "2006-07-20T19:24:44Z")
> [@Valteron](#): > > Since dinosaurs existed for hundreds of millions of years (meaning billions upon tens of billions of individual animals) and since some of those lads had a bladder the size of a Volkswagen, it is almost CERTAIN, I would think, that we have ingested a water molecule once pissed out by a dinosaur. You could be right: There are 3.612 X 10^20 gallons of water on earth. The volume of a Volkswagon is 2764 gallons. That’s 1.306 X 10^17 dino bladders worth of water. Dinos lasted for about 100 million years. Even if there are a continous population of 1 million dinos on Earth for every one of those years, that would account for 2.764 X 10^17 gallons of dino piss. In fact, every gallon may have made the trip through a dino bladder twice! ---
**Author:** ![Alive\_At\_Both\_Ends](https://avatars.discourse-cdn.com/v4/letter/a/73ab20/32.png) [@Alive\_At\_Both\_Ends](https://boards.straightdope.com/u/Alive_At_Both_Ends)\ **Post date:** [July 20, 2006, 7:41pm UTC](https://boards.straightdope.com/t/geneologists-and-geneticists-how-closely-related-are-all-humans/365346/9 "2006-07-20T19:41:31Z")
> [@Valteron](#): > > Seriously, then, how likely is it that say, a Nazi or a KKK or Aryan Front member has a black person, a semite (Jewsish or Arab) or an asiatic or Amerindian somewhere in their geneology if you go back through ALL their ancestors, following the male and female lines and all granparents, etc.? Say if you go back 100 generations, which would be about 2,500 years, or about the time of Alexander the Great? How likely is it? Since all humans are descended from an original group of people in East Africa, the probability is 1. Even if you limit it to 2500 years the probability is as near 1 as makes no difference. Eighty generations ago, the Roman Empire was at its height; it knew no colour bar; and people moved freely through it. Its citizens included North Africans and Middle Easterners as well as Europeans. Everyone of European ancestry alive today will have a vast number of ancestors who lived in the Empire. The conclusion isn’t hard to reach. Even the SS in Nazi Germany didn’t take racial purity to that extreme. SS officers were only required to prove they had no Jewish ancestry since 1750. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [July 20, 2006, 7:43pm UTC](https://boards.straightdope.com/t/geneologists-and-geneticists-how-closely-related-are-all-humans/365346/10 "2006-07-20T19:43:53Z")
> [@Valteron](#): > > Seriously, then, how likely is it that say, a Nazi or a KKK or Aryan Front member has a black person, a semite (Jewsish or Arab) or an asiatic or Amerindian somewhere in their geneology if you go back through ALL their ancestors, following the male and female lines and all granparents, etc.? Say if you go back 100 generations, which would be about 2,500 years, or about the time of Alexander the Great? How likely is it? I don’t know how you’d calculate that probability, but unless the KKK member’s parents are recent immigrants from some small village in a remote part of Europe, I’d say the odds wouldbe quite high. By the one-drop-rule, we might consider QE II to be Black-- she has a Portuguese ancestor who was supposedly of mixed European and African heritage. ---
**Author:** ![Valteron](https://avatars.discourse-cdn.com/v4/letter/v/f17d59/32.png) [@Valteron](https://boards.straightdope.com/u/Valteron)\ **Post date:** [July 20, 2006, 9:01pm UTC](https://boards.straightdope.com/t/geneologists-and-geneticists-how-closely-related-are-all-humans/365346/11 "2006-07-20T21:01:44Z")
> [@John Mace](#): > > By the one-drop-rule, we might consider QE II to be Black-- she has a Portuguese ancestor who was supposedly of mixed European and African heritage. Fascinating idea. Queen Elizabeth comes on stage with her hair in corn rows and in a gingham dress, and sings: “Fish gotta swim, birds gotta fly Gonna be Queen till the day I die Can’t help, wearin’ that crown of mine!” ---
**Author:** ![kimera](https://avatars.discourse-cdn.com/v4/letter/k/f0a364/32.png) [@kimera](https://boards.straightdope.com/u/kimera)\ **Post date:** [July 20, 2006, 9:56pm UTC](https://boards.straightdope.com/t/geneologists-and-geneticists-how-closely-related-are-all-humans/365346/12 "2006-07-20T21:56:36Z")
> [@Valteron](#): > > Seriously, then, how likely is it that say, a Nazi or a KKK or Aryan Front member has a black person, a semite (Jewsish or Arab) or an asiatic or Amerindian somewhere in their geneology if you go back through ALL their ancestors, following the male and female lines and all granparents, etc.? It might not even be that far back. I am lilly white and I have difficulty finding foundation that matches my pale skin tone. Two of my brothers are very Nordic looking - tall (6 foot +), blond, and blue eyed. However, all of us have Native American/African blood running through our veins. We did genetic testing to find out if my mother’s geneological findings were close to the truth and we were surprised to find the concentration of African/Native American blood. We suspected that we found find Native American blood, because one of my American ancestors was said to have married a Native American woman, but the African blood was a surprise.