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Author | Topic: Hello, cousin! (re: Recent common ancestors to all living humans) | |||||||||||||||||||||||||
subbie Member (Idle past 1282 days) Posts: 3509 Joined: |
According to a recent statistical analysis, all humans probably descend from one person who lived between 2,000-5,000 years ago, and all people who were alive 5,000-7,000 years ago whose lines did not die out are all ancesters to everyone now alive.
Brotherhood of Man My knowledge of statistics is far too limited to even begin to understand the analysis presented in the article, but the discussion is fascinating. It certainly gives the lie to any claim that any "race" is more advanced than any other, at least as far as any scientific discussion is concerned. Evolution doesn't proceed anywhere near the pace that would be required for there to be any but superficial differences between "races." Adminnemooseus suggested that this topic belongs in Human Origins. Edited by Adminnemooseus, : Added the "(re: Recent common ancestors to all living humans)" part to the topic title. I must file the original title under "cute but pretty worthless". It is my unrealized hopes that such topic titles get fixed before the topic is promoted out of the "Proposed New Topics" forum. I also don't understand why this topic wasn't promoted to the "Human Origins" forum. Those who would sacrifice an essential liberty for a temporary security will lose both, and deserve neither. -- Benjamin Franklin
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AdminNosy Administrator Posts: 4754 From: Vancouver, BC, Canada Joined: |
Thread moved here from the Proposed New Topics forum.
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Jazzns Member (Idle past 3939 days) Posts: 2657 From: A Better America Joined: |
Of course the creationists will jump on this because it fits their style.
Seems simple, just extrapolate back the generations and at some point you have more ancestors then there were people on the earth. One problem I can see other than how unrealistic the result is is simply that it makes no account for regional seperation. I am sorry but at 2k-5k BC I am pretty confident that none of my ancestors were Austrailian Aborigines nor Native American. Of course, biblical creationists are committed to belief in God's written Word, the Bible, which forbids bearing false witness; --AIG (lest they forget)
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subbie Member (Idle past 1282 days) Posts: 3509 Joined: |
Apparently you didn't read the whole article.
The model also had to allow for migration based on what historians, anthropologists and archaeologists know about how frequently past populations moved both within and between continents. Rohde, Chang and Olson chose a range of migration rates, from a low level where almost nobody left their native home to a much higher one where up to 20 percent of the population reproduced in a town other than the one where they were born, and one person in 400 moved to a foreign country. Now, if you wish to question the methodolgy, the statistics or the range of migration rates used, that's fine. But to simply state they didn't account for regional separation when the article clearly says that they did seems disingenuous to me. Those who would sacrifice an essential liberty for a temporary security will lose both, and deserve neither. -- Benjamin Franklin
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Jazzns Member (Idle past 3939 days) Posts: 2657 From: A Better America Joined: |
How much migration was there between Australia, North America, and Eurasia 2k to 5k years ago?
Certainly they talk about it, but in no way does it seem that it was adequetly or accuratly accounted for in their conclusion. This quote for me certainly raised a red flag.
Allowing very little migration, Rohde's simulation produced a date of about 5,000 B.C. for humanity's most recent common ancestor. Assuming a higher, but still realistic, migration rate produced a shockingly recent date of around 1 A.D. If someone could calculate a "realistic" migration rate between Native Australian and European people then that alone would probably be news worthy. What it sounds like they are doing is applying a rate taken from analyzing some migration dynamics and applied it to the whole population. A step that if true would be very much invalid. The other think you should note is that by slightly changing their "rate" they give a number that I would be hightly skeptical of 1 A.D. I would need more details to be sure but at first glance that just seems rediculous. Of course, biblical creationists are committed to belief in God's written Word, the Bible, which forbids bearing false witness; --AIG (lest they forget)
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pink sasquatch Member (Idle past 6050 days) Posts: 1567 Joined: |
I tracked down the original Nature article, unfortunately it requires a subscription:
Modeling the recent common ancestry of all living humans. One thing I'm a bit confused about - the paper is almost two years old, yet the Yahoo news article seems to treat it a recent discovery... I have a problem with the Yahoo news version of the research - the typical translation-to-laymenspeak problems seem to exist:
Yahoo News version: Furthermore, Olson and his colleagues have found that if you go back a little farther ” about 5,000 to 7,000 years ago ” everybody living today has exactly the same set of ancestors. Original report version: That is, each individual living at least U-subN generations ago was either a common ancestor of all of today's humans or an ancestor of no human alive today. "U-subN" generations is an abstract theoretical variable in a simplified model. It does not equal ~6000 years in any real way. Much of the paper is description of assumptions and simplifications of the model. From the conclusion:
Given the remaining uncertainties about migration rates and real-world mating patterns, the date of the MRCA for everyone living today cannot be identified with great precision. It would be interesting to see how the mathematical model compares to genetic data regarding the MRCA (most recent common ancestor).
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Larni Member Posts: 4000 From: Liverpool Joined: |
I would doubt this is much more than (as has been noted) putting a layman filter over some stats.
My 'Big Book of Caveman' put mitochondial Eve at 200,000 BCE. It also states (on a particularly colourfull pop up page) that at about 150,000 there was a bottleneck in the gene pool as the popn fell to a few 10s of thousands. Pushing this forwards to about 5-7k simply by plugging an arbitary number into a computation seems foolish. This coupled with the logical arguement about migration featured above makes my think this artical is not saying what it is puported to.
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nwr Member Posts: 6412 From: Geneva, Illinois Joined: Member Rating: 4.5 |
You might have misunderstood this. It is not suggesting a bottleneck at 5-7k (or anywhere). It is saying that, at 5-7k ago, I had many many many great great great .... grandmothers, so many that the chances are that you too are descended from at least one of them. No bottleneck is required.
I share Jazzns skepticism with regard to relatively isolated populations such as the Australian aboriginals. But it could still be correct if there was a small amount of gene flow between them and pacific islanders.
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RAZD Member (Idle past 1432 days) Posts: 20714 From: the other end of the sidewalk Joined: |
a range of migration rates, from a low level where almost nobody left their native home to a much higher one where up to 20 percent of the population reproduced in a town other than the one where they were born, and one person in 400 moved to a foreign country.
But to simply state they didn't account for regional separation when the article clearly says that they did seems disingenuous to me. The point was the physical barriers between the different areas, North\South America and Australia are much much more difficult than moving from, say, France to Spain. Different country is not different continent. The mathematics obviously did NOT account for any differences in ability to migrate to different places, but then mathematical models are always limited in their reflection of the real world From the article:
"It's a mathematical certainty that that person existed," said Steve Olson, whose 2002 book ... Nope. The math is only as good as the assumptions and the model representing reality.
How can this be? It's simple math. Every person has two parents, four grandparents and eight great-grandparents. Keep doubling back through the generations ” 16, 32, 64, 128 ” and within a few hundred years you have thousands of ancestors. It's nothing more than exponential growth combined with the facts of life. By the 15th century you've got a million ancestors. By the 13th you've got a billion. Sometime around the 9th century ” just 40 generations ago ” the number tops a trillion. But wait. How could anybody ” much less everybody ” alive today have had a trillion ancestors living during the 9th century? The answer is, they didn't. Imagine there was a man living 1,200 years ago whose daughter was your mother's 36th great-grandmother, and whose son was your father's 36th great-grandfather. That would put him on two branches on your family tree, one on your mother's side and one on your father's. And all you need to do is keep that on a regional basis mathematically to account for all the relationships necessary to double up the ancestors rather than have an expotential growth pattern on them. This does NOT mean that people in africa, america, australia and asia HAD to interbreed to account for the numbers of ancestors. Bad math, bad logic, bad conclusion. Enjoy. we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist
... to learn ... to think ... to live ... to laugh ... to share.
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pink sasquatch Member (Idle past 6050 days) Posts: 1567 Joined: |
The mathematics obviously did NOT account for any differences in ability to migrate to different places, Wrong. The majority of the report focuses on approximating regional differences in migration through history. They also incorporate colonization-related bursts of migration; in other words, they don't entirely assume a constant rate of migration over time. As an example, the model assumes one-hundred individuals per generation migrate between northern Africa and Italy, while only one individual per generation migrates between New Zealand and Polynesia. The model is still mathematical, still rest on assumptions, and is thus not an accurate depiction of reality. However, to simply dismiss it as a simple exponential model without, apparently, even examining the model (or even reading the abstract of the paper) is extremely problematic.
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RAZD Member (Idle past 1432 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Wrong. The majority of the report focuses on approximating regional differences in migration through history. ... As an example, the model assumes one-hundred individuals per generation migrate between northern Africa and Italy, while only one individual per generation migrates between New Zealand and Polynesia. That still does not get you over the physical barriers between europe and the americas before columbus, for instance, which is then lumped in with the migration rate from New Zealand and Polynesia? Jazzns in Message 3 and Message 5 addresses some of this issue.
However, to simply dismiss it as a simple exponential model without, apparently, even examining the model (or even reading the abstract of the paper) is extremely problematic. I look at the process as described in both the "sensational press" article and what is available in the abstract, and what I see is a model that essentially draws concentric circles around an idealized homogeneous population, and assigns different migration rates to the different radii of the circles in an inverse relationship. This basically says a LOT of close regional inter-breeding of nearby populations, and less and less interbreeding between distant populations. Now you can cover the earth with these averaged migration circles but there are places where they just don't fit the geography. I don't see any correction for geography, and find that rather significant. The abstract says:
These analyses suggest that the genealogies of all living humans overlap in remarkable ways in the recent past. In particular, the MRCA of all present-day humans lived just a few thousand years ago in these models. That doesn't tell me how pre-christian egyptians could mix genes with inhabitants of Chilca Valley, for example. It explains how populations on different continents can "overlap in remarkable ways in the recent past" but NOT that it in fact happened or that populations between different continents HAD to overlap at all. The problem with this "MRCA" conclusion is that it just doesn't follow from the premises, for a number of reasons.
This study is not based on genetics, or geography, or even history (beyond 'cherrypicking' some historical parameters), but on what is possible mathematically given certain parameters and restrictive conditions and enabling assumptions. Claiming what is possible mathematically in an idealized structured {environment\population}, as something that then had to have occurred to all humans around the world is a logical leap that is totally unwarranted. Enjoy. Edited by RAZD, : clarified history we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist
... to learn ... to think ... to live ... to laugh ... to share.
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pink sasquatch Member (Idle past 6050 days) Posts: 1567 Joined: |
That still does not get you over the physical barriers between europe and the americas before columbus, The model takes this into account - no migration until it starts at a very low rate from Europe to North America via Iceland/Greenland in 1000 AD. Migration across the Bering Strait region begins at 12000 BC in the model. North America is not a single unit - migration dynamics within North America are also modeled.
which is then lumped in with the migration rate from New Zealand and Polynesia Huh? Where the hell did you come up with that one?
I look at the process as described in both the "sensational press" article and what is available in the abstract, and what I see is a model that essentially draws concentric circles around an idealized homogeneous population, and assigns different migration rates to the different radii of the circles in an inverse relationship. Then "what you see" is wrong, because it does not accurately describe the model, which takes into account historical differences in migration rates within a nodal model. You might realize this if you read more than the abstract and the lay press version of the research. It is rather ignorant and rude to severely criticize research and researchers without ever examining the actual research in question.
I don't see any correction for geography, and find that rather significant. You would see that correction if you read the paper. Read the paper before you criticize. I'm not going to bother responding to the rest of your post for what should be an obvious reason.
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Jazzns Member (Idle past 3939 days) Posts: 2657 From: A Better America Joined: |
The study itself may be awesome but do you think the "made for TV" version of the study does it justice or uses the findings from the study accuratly?
Even though that is not what RAZD is saying, I think that is what he means. Without being an expert on the subject, it "seems" to be the case that the 2k-5k number is way off and may be a bastardization of the real science. Of course, biblical creationists are committed to belief in God's written Word, the Bible, which forbids bearing false witness; --AIG (lest they forget)
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pink sasquatch Member (Idle past 6050 days) Posts: 1567 Joined: |
do you think the "made for TV" version of the study does it justice or uses the findings from the study accuratly? See my message #6 above. Even though that is not what RAZD is saying, I think that is what he means. I think RAZD is a smart enough guy to say what he means. I still think it is inexcusable to so severly criticize a model that you haven't examined in any way. The bulk of his criticisms, (which are extensive and detailed), rest on assumptions about the model that are not true.
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Jazzns Member (Idle past 3939 days) Posts: 2657 From: A Better America Joined: |
So basically RAZD's problems are true if you only examine the sensationalized article. Are we all just agreeing differently that the Yahoo article is a misrepresentation if not wrong all together?
Of course, biblical creationists are committed to belief in God's written Word, the Bible, which forbids bearing false witness; --AIG (lest they forget)
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