WordsOnImages is where users Discover & Share Inspiring Pictures & Famous quotes about Life, Love, Friendship, Success, Happiness and various other topics. The only way out of this paradox is to assume that our ancestors are not independent of one another. As you go back further in time, more of those lines cross as you encounter more common ancestors of the living population. In 2002, the journalist Steven Olson wrote an article in the Atlantic about Chang’s work.
The most recent common ancestor of every European today (except for recent immigrants to the Continent) was someone who lived in Europe in the surprisingly recent past—only about 600 years ago. Things have changed a lot in the fourteen years since Chang published his first paper on ancestry. Recently, two geneticists, Peter Ralph of the University of Southern California and Graham Coop of the University of California at Davis, decided to look at the ancestry of Europe. You can use this kind of genetic information to make some genealogical inferences, but you have to know what you’re dealing with. This means that if you compare two people’s DNA, you will find some chunks that are identical in sequence. Ralph and Coop identified 1.9 million of these long shared segments of DNA shared by at least two people in their study. Their results, published today in PLOS Biology, both confirm Chang’s mathematical approach and enrich it.
Ralph and Coop’s study may provide a new tool for reconstructing the history of humans on every continent, not just Europe. Fortunately, Ralph and Coop have written up a helpful FAQ for their paper, which you can find here. That is really interesting, but it doesn’t explain how all people on earth can have a common ancestor 3400 years ago when the populations are seperated by so much distance. Very cool, any idea of the percentage of folk today descended from that standard of mega-reproduction Genghis Khan?
When ancestry testing becomes commonplace, I wonder if people along HMS Beagle’s route will find Darwin in their past. How could a European and an aboriginal Australian, for example, possible have a common ancestor who lived only 3400 years ago, our common ancestors having left Africa 50,000 odd years ago and gone in different directions to opposite sides of the world? We’re not talking here about how many people have a reliable paper trail to Charlemagne. Have to agree with Phil Kent — if the calculations are mathematically correct, then they must have made poor assumptions about mixing of populations around the world. In fact we can push this further, anyone who was alive 1000 years ago, and whose descendants hadn’t died out after ~10 generations is very likely to be an ancestor to the entire population. Putting the genetics aside, it is very likely, given that he lived ~800 years ago, that many people in that area [and indeed more widely] can trace their ancestry back to him [and in fact to many people alive at that time, for similar reasons as I outlined above].
Peter Ralph and I have discussed following up on his genetic impact through similar techniques to those used in our article. We have good depictions of the ancient Greeks from more than 2400 years ago, in which they are clearly recognisable as fair-skinned Europeans, as phenotypically distinct from other races from other continents are Europeans still are today, the importance of which lies in man’s inherent and intense tribal nature and need to identify with a particular tribe. Race and ethnic origins, I content, are central to any deep and meaningful sense of both personal and group, i.e.
A different end of things I’ve wondered about is from the fact that we have so few genes. Which leads to the peculiar conclusion that he’s our ancestor, but we probably have none of his genes. In response to a European and Australian having a common ancestor, a man or woman in East Asia 4000 years ago might have had children who married and moved a few miles away.
You (and some others) have taken this to imply that everyone should be nearly genetically identical (and indeed we are, relative to chimpanzees, but that’s another story).
We are certainly not saying that all genetic differences between individuals have arisen in the past few thousand years (that simply is not true).
Our calculations in the paper are based on these types of calculations, for example we find that pairs of people as far apart as the UK and Turkey share a largish chunk of genomic material 20% of the time. Now consider that we arrange to have the most disparate possible set of descendents — person number 1 appears _only_ as the parent of people who are also descended from person #2, and so forth. The exponential growth of ancestors mean that after 14 generations, call it 1600, you’d need a city of population well over 16,000 (2^14)to avoid everybody being related to everybody today. At 28 generations, still far short of Charlemagne (very great grandpa Chuck), say 1180, you have to have a population of over 256 million, and optimal divergent mating, in order to avoid there being somebody who was ancestral to everybody.
The only way to get a date of common ancestry as _large_ as 3400 years (over 100 generations) is if you do indeed have populations relatively isolated from each other for much of that time.


It’s a cute thing to focus on a single common ancestor, but the more important questions involve who is more related to whom. When I was young I thought that money was the most important thing in life; now that I am old I know that it is. Our ambition should be to rule ourselves, the true kingdom for each one of us; and true progress is to know more, and be more, and to do more.
There is only one thing in life worse than being talked about, and that is not being talked about.
If one cannot enjoy reading a book over and over again, there is no use in reading it at all.
Selfishness is not living as one wishes to live, it is asking others to live as one wishes to live. Thanks for viewing "Lost Love Quotes".You can also find us on popular social media sites including Facbook, Pinterest, Google+ & Tumblr. I vaguely recall that an ancestor of mine who shipped over on the Mayflower distinguished himself by falling out of the ship and having to get fished out of the water. Instead, he is a statistician at Yale who likes to think of genealogy as a mathematical problem.
If you look at the ancestry of a living population of people, he concluded, you’ll eventually find a common ancestor of all of them.
In other words, all Europeans alive today have among their ancestors the same man or woman who lived around 1400.
Scientists have amassed huge databases of genetic information about people all over the world. They took advantage of a compilation of information about 2257 people from across the continent.
They then used the length of each segment to estimate how long ago it arose from a common ancestor of the living Europeans. Since they live in the same country, chances are they have more recent ancestors, and more of them.
It’s not strange to say that millions of people living today are descendants of a couple who lived a thousand years ago or even a single individual. There are populations that have been separated for too long for 3400 years to work for a most recent common ancestor.
Rohde, Olsen, and Chang in their earlier paper [linked to by Carl above] do a pretty thorough job of examining how little migration you would need to still have their result about world-wide relationships.
We found it through Nick Patterson, but in general many people are stuck on the 20 years number [for no obvious reason, other than reference inertia I suspect]. We’ve also wondered about publishing an accessible explanation of the math underlying these calculations, as many of these calculations are slightly tricky to get to [but quite easy to explain once you see the logic]. This really confirms the presence of a rigid class system which in turn undermines the random mixing assumption that underlies the mathematical modelling that has been done here. Rohde et al’s result of ~3500 years, is the predicted time for ALL of humanity to be genealogically related. Yes you are right, being a genealogical ancestor is no guarantee of having contributed genomic material to a descendant. Since the chance that two people inherit genetic material from any one shared ancestor from 1,000 years ago is incredibly unlikely (<10^(10)), to explain such sharing we need these pairs of individuals to share many ancestors. Bush might indeed be descended by 1 path from n!Xao, a Bushman in the Kalahari, but he’d also be descended from Owen, a farmer in Essex, by 800,000,000 different paths. When you draw your genealogy, you make two lines from yourself back to each of your parents.
That’s not to say that a single mythical woman somehow produced every European by magically laying a clutch of eggs.
These may not be the same thing as a complete genealogy of the human race, but geneticists can still use them to tackle some of the same questions that intrigued Chang. Scientists had examined half a million sites in each person’s DNA, creating a distinctive list of genetic markers for each of them. Each time they made eggs or sperm, they shuffled the two copies of each of their chromosomes and put one in the cell. This diagram shows how two first cousins share a piece of DNA that’s identical by descent (IBD for short). If Europeans today share the same ancestors a thousand years ago, for example, why don’t they all look the same? The chances can not be reversed, the total set of my ancestors in the year 1000 was percentage X. However, the rate of migration between most locations in Eurasia and Africa has been high enough that if we, for example, think about individuals drawn from across Africa, Asia, and Europe they share the majority of their ancestors even more recent than that.


I for one am fascinated by how adaptation has shaped phenotypic diversity and our genomes over the past 100,000 years as humans have spread around the world (and have worked on this topic extensively). In fact, they need to share a number of ancestors that is far larger than the size of European population, indicating that any pair of individuals share as ancestors all of the individuals alive back at the time in Europe, each many times over. I would have thought, however, that this issue could be resolved simply by comparing our DNA profiles.
And, the boy who sees the thing of beauty which a bird on the wing becomes when transferred to wood or canvas will probably not throw the customary stone.
This means that instead of drawing a tree that fans out exponentially, we need to draw a web-like tapestry. All this means is that as you move back through time, sooner or later some of the lines in the genealogy will cross, meeting at a single person.
Just as a new deck gets more scrambled the more times you shuffle it, chromosomes get more shuffled from one generation to the next. In fact, as Chang suspected, the only way to explain the DNA is to conclude that everyone who lived a thousand years ago who has any descendants today is an ancestor of every European.
People across Eastern Europe, for example, have a larger set of shared segments than people from within single countries in Western Europe. India also had connections with Southeast Asia (that’s why Bali is Hindu even today). The key to these counter intuitive results is that you number of ancestors grows very fast indeed (2^k, k generations ago).
However, as you note, when discussing the spread of genealogical ancestry these rare events matter a lot. Anyone around a thousand years ago in Europe, who left any descendant to the present day, is likely an ancestor to everyone in Europe (i.e.
It isn’t plausible if we want to claim that it is simply due to the fact that Genghis Kahn himself had a lot of children, although this is necessary. This is a very solid result, and reflects the huge number of ancestors you have 3500 years ago.
However, that work is all against the backdrop that the majority of genetic variation, and indeed the majority of trait variation, is found within all human populations, and very little variation shows a hard-and-fast distinction between populations. That’s because you inherit your genome from your parents in large chucks that are often ? a chromosome in length, consisting of many genes. Chang figured that out by expanding his model from living Europeans to living humans, and getting an estimate of 3400 years instead of a thousand for the all-ancestor generation. It’s not too difficult to see how some powerful Raja in India could sire (mostly illegitimate) descendants who went both west and east. Because when families had 10, 12, 15, 20 children and lived in communities amongst the same families for generations, those families intermarried NUMEROUS times with siblings from the same family marrying siblings from the other families. That means that even a very low rate of migrants will still guarantee that even seemingly very isolated groups will be able to trace their ancestry back to one of these very rare migrants, and hence the rest of the world. However, if his sons and grandsons also had a lot of kids, and that this male line success to continue for a number of generations beyond that, then his Y chromosome could have spread that much. Back then you have 2^116 ancestors that’s roughly: 30 million, billion, billion ancestors, its hard to imagine that those are not shared with the majority of people alive today. Nobody actually doubts that, but when journalists start talking about genealogy, they quickly get bogged down in essentially symbolic thinking, in which having one ancestor from ethnic group X is somehow just as important as having many millions from ethnic group Y.
This also follows from the fact that your family tree branches very rapidly backward in time, so [as laid out by Chang and others]. I also did a bunch of calculations about how much of a genetic contribution he alone made to the average modern person in that area, but that is much smaller on the autosomes [i.e. Looking back up your family tree that means that as we follow the chunks of your genome is spread across your ancestors in any one generation (see Figure 1 of our paper). If you go back to the time of Charlemagne, forty generations or so, you should get to a generation of a trillion ancestors. The indian trade routes were quite extensive, and war was often, just as in europe around that time. The further back we go the smaller these chunks are, as they’ve been through more generations of recombination, but the number of genomic chunks increases only slowly compared to how quickly the number of your ancestors.
That’s about two thousand times more people than existed on Earth when Charlemagne was alive.



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