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Author Topic:   Hello, cousin! (re: Recent common ancestors to all living humans)
subbie
Member (Idle past 70 days)
Posts: 3508
Joined: 02-26-2006


Message 1 of 76 (328556)
07-03-2006 1:11 PM


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
Replies to this message:
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AdminNosy
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Joined: 11-11-2003


Message 2 of 76 (328560)
07-03-2006 1:23 PM


Thread moved here from the Proposed New Topics forum.
  
Jazzns
Member (Idle past 2021 days)
Posts: 2657
From: A Better America
Joined: 07-23-2004


Message 3 of 76 (328568)
07-03-2006 1:56 PM
Reply to: Message 1 by subbie
07-03-2006 1:11 PM


Seems Bogus
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 70 days)
Posts: 3508
Joined: 02-26-2006


Message 4 of 76 (328577)
07-03-2006 2:12 PM
Reply to: Message 3 by Jazzns
07-03-2006 1:56 PM


Re: Seems Bogus
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 2021 days)
Posts: 2657
From: A Better America
Joined: 07-23-2004


Message 5 of 76 (328592)
07-03-2006 3:13 PM
Reply to: Message 4 by subbie
07-03-2006 2:12 PM


Re: Seems Bogus
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 4133 days)
Posts: 1567
Joined: 06-10-2004


Message 6 of 76 (328645)
07-03-2006 6:20 PM
Reply to: Message 1 by subbie
07-03-2006 1:11 PM


comparison to primary article
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: 3976
From: Liverpool
Joined: 09-16-2005


Message 7 of 76 (328879)
07-05-2006 6:01 AM
Reply to: Message 1 by subbie
07-03-2006 1:11 PM


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: 5585
From: Geneva, Illinois
Joined: 08-08-2005


Message 8 of 76 (328888)
07-05-2006 7:22 AM
Reply to: Message 7 by Larni
07-05-2006 6:01 AM


No bottleneck
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
Posts: 19819
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 10.0


Message 9 of 76 (328891)
07-05-2006 7:40 AM
Reply to: Message 4 by subbie
07-03-2006 2:12 PM


mathematic models again?
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.


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pink sasquatch
Member (Idle past 4133 days)
Posts: 1567
Joined: 06-10-2004


Message 10 of 76 (329002)
07-05-2006 3:04 PM
Reply to: Message 9 by RAZD
07-05-2006 7:40 AM


Re: mathematic models again?
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.


This message is a reply to:
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RAZD
Member
Posts: 19819
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 10.0


Message 11 of 76 (329094)
07-05-2006 9:23 PM
Reply to: Message 10 by pink sasquatch
07-05-2006 3:04 PM


Re: mathematic models again?
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.

  1. One is that it assumes a homogeneous distribution in a homogeneous environment, with the only variable being rates of migration inversely proportional to distance by some averaged metric (whatever formula they used).

    This may be coming true with a global airtravel society, but it certainly did not exist pre-columbus. See (3).

  2. The idea of a single MRCA organism within a sexually reproducing population is bogus, therefore any conclusion based on it is bogus.

    You can take a population of say 200,000 individuals and every year for 1,000 years {protect\cull} the population so that there are always 200,000 individuals and at the end of that time genetically find out that they are all related in the recent past because of the shared genetic material, but at no time in the past was there a single individual with those shared genetics -- they have been combined from the resources of the whole population, picking the ones from different individuals that are "less costly" ... think of it as selecting gene Q from individual Q's offspring for environmental\sexual (E/S) factor Q, selecting gene R from individual R's offspring for (E/S) factor R, selecting gene S from individual S's offspring for (E/S) factor S, selecting gene T from individual T's offspring for (E/S) factor T, etcetera: the final population genetics will "find" a "MRCA" with Q, R, S, T, etc, genes when no single ancestor had them all. You can also have the same amount, more or less genetic diversity than when you started - there was no control on diversity along the way.

    I have the same problem with "genetic eve" and "genetic adam" btw, because there is no reason for all the genes to come from any single individual when so many ancestors have "participated" along the way and the population group is always intermixing the available genetic material in new combinations.

    You could keep this going for millions of years, and you would find, with continued evolution and natural selection, that you reach a point of equilibrium where you would always find a theoretical "MRCA" of the essentially the SAME age in each population no matter when you picked your sample, because you would only have so much material to work with.

    This is the essence of population mixing that results in new species when different populations are sufficiently isolated in space or time.

  3. Very recent (ie since columbus) migration and conquest\control and disease etc patterns have significantly shifted the genetic panorama, causing a level of genetic mixing much higher than previously and on more and more of a world wide level, this results in mixing the genetics of several previously isolated "MRCA" populations with some parts of some being selected over others and some not -- the result is NOT a "new" ancestor.

    Take the example above of a closed population of 200,000 individuals and repeat that with two or three others, after 1000 years mix them all together for what, 340 years or so? You can then derive a new theoretical "MRCA" that has even less basis in reality than the ones derived for each such population.


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


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RebelAAmericanOZen[Deist
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This message is a reply to:
 Message 10 by pink sasquatch, posted 07-05-2006 3:04 PM pink sasquatch has responded

Replies to this message:
 Message 12 by pink sasquatch, posted 07-06-2006 11:00 AM RAZD has responded

  
pink sasquatch
Member (Idle past 4133 days)
Posts: 1567
Joined: 06-10-2004


Message 12 of 76 (329311)
07-06-2006 11:00 AM
Reply to: Message 11 by RAZD
07-05-2006 9:23 PM


wrong again...
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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Replies to this message:
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Jazzns
Member (Idle past 2021 days)
Posts: 2657
From: A Better America
Joined: 07-23-2004


Message 13 of 76 (329317)
07-06-2006 11:12 AM
Reply to: Message 12 by pink sasquatch
07-06-2006 11:00 AM


Re: wrong again...
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)
This message is a reply to:
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pink sasquatch
Member (Idle past 4133 days)
Posts: 1567
Joined: 06-10-2004


Message 14 of 76 (329333)
07-06-2006 11:47 AM
Reply to: Message 13 by Jazzns
07-06-2006 11:12 AM


Re: wrong again...
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.


This message is a reply to:
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Replies to this message:
 Message 15 by Jazzns, posted 07-06-2006 1:19 PM pink sasquatch has responded

  
Jazzns
Member (Idle past 2021 days)
Posts: 2657
From: A Better America
Joined: 07-23-2004


Message 15 of 76 (329387)
07-06-2006 1:19 PM
Reply to: Message 14 by pink sasquatch
07-06-2006 11:47 AM


Re: wrong again...
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)
This message is a reply to:
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