Humans Migrated Out Of Africa, Then Some Went Back, Study Says

National Geographic Society ^ | 12-14-2006 | Stefan Lovgren

[blam]

Humans Migrated Out of Africa, Then Some Went Back, Study Says

Stefan Lovgren
for National Geographic News

December 14, 2006

Humans first moved out of Africa about 70,000 years ago, but 30,000 years later some of them moved back.

That's according to a new study based on DNA evidence from ancient human remains found in Africa.

The study shows that a small group of early humans returned to Africa after migrating to the Middle East.

In addition, the research suggests that the humans' return occurred around the same time that another group of humans left the Middle East and moved into Europe.

"We were rather surprised by the age of the migration back to Africa," said Antonio Torroni, a geneticist at the University of Pavia in Italy.

"We did not really expect that it was 40,000 to 45,000 years old."

"But the age and the fact that the migration had originated in the Levant [a geographical term referring to a large part of the Middle East] led us to link the migration to Africa to that occurring at the same time toward Europe from the same region," added Torroni, who led the research team.

The findings are reported in tomorrow's issue of the journal Science.

Single Dispersal

The new study builds on the theory, laid out in two separate studies published in Science last year, that humans migrated from Africa in a single dispersal about 70,000 years ago.

That theory suggests that modern humans left East Africa by crossing the Red Sea, then journeyed south, following a coastal route along the Arabian Peninsula and on to India, Malaysia, and Australia (see a map of human migration). Other models have suggested that humans left Africa in multiple waves of migration via northern and southern routes.

The single "out of Africa" dispersal is believed to have given rise to all modern non-African populations.

However, scientists have been puzzled by two genetic populations found only in northern and eastern Africa, whose ancestors appear to have been Asian.

In the new study, scientists sequenced the mitochondrial DNA, which is passed from mother to daughter, from 81 individuals in both of these genetic groups.

They found that the two populations must have arisen in southwestern Asia and returned to Africa about 40,000 to 45,000 years ago.

The groups did not, however, follow the same southern coastal route back that was used in the single dispersal out of Africa.

Instead, the study suggests, they arrived from the Middle East, the same area from which another genetic group—one typical among Europeans—was at the same time moving toward Europe.

"It's a finding that … supports the view that the first [Late Stone Age] cultures in North Africa and Europe had a common homeland in the Levant," Torroni said.

Vincent Macaulay, the lead author on one of the two single-dispersion studies published in Science last year, agrees with the findings.

"These results make perfect sense and wrap up some loose ends," said Macaulay, a genetic statistician at the University of Glasgow in Scotland.

Changing Climate

The authors of the new study believe that before reaching the Levant, migrating humans may have paused at the Persian Gulf for some time because of a hostile climate.

Environmental evidence suggests that migrating north from southwestern Asia would have been impossible earlier than 50,000 years ago because of a vast desert that extended from northern Africa to central Asia.

"When weather conditions improved, the desert was fragmented and reduced in size," said Anna Olivieri, a geneticist in Torroni's lab and a co-author of the study.

"The human groups living in the coastal regions of southwestern Asia were able to move inland."

"Some of them colonized first the Levant and from there all surrounding regions including Europe and North Africa," she said.

"Consider also that the Sahara desert in North Africa was reducing its size. Thus, that region became interesting from a human colonization perspective."

[kinoxi]

That's about what I got out of it. Clearly suspect methodology to predetermine the mutation rate from supposition rather than observation. I found the part where examples of males transferring mitochondrial DNA to be the nail in the coffin of this theory though.

[skippermd]

This raises 3 fundamental questions for me that I pose to any anti-creationism person:
1. If humans arose from more primitive animals, why just in one spot near the equator? Why didn't the monkeys we came from migrate first?

2. I'm pretty sure C14 dating is not accurate for samples over 40,000 years old (its actually never been proven accurate for samples over 2000 years old) so this is based on archeological evidence for the 80,000 years ago mark? How do you know that the flood did not skew these results...

3. DNA is DNA wherever it is in the cell, it is extremely susceptible to damage and mitochondrial DNA is especially conserved through species and even more within the human race. If you are using this to track migration, its more likely that you're seeing different results from mutation than place of origin...

Just my humble opinion

[blam]

"The Toba eruption could very well have driven humans south in to Australia.. ( 6 year "nuclear" winter, subsequent 1000 year ice age provides adequate ice-overs in the southern hemisphere for desperate humans to attempt escaping disaster ) "

Some human activity/artifacts have been found in Indonesia that date to shortly after Toba exploded. No-one knows if they survived the 'winter' caused by Toba...they apparently did survive the explosion for some time afterward.

[blam]

"more contrived feelgood therapy for the afrocentrists"

All humans come from lines designated L1, L2, and L3. Everyone outside Africa are descended from L3 and are more related to themselves than anyone in Africa. The L1 and L2 lines are still in Africa but, the L3 line has gone extinct in Africa.

[Coyoteman]

I'm presently reading a book titled, Before The Dawn, by Nicholas Wade and he says that the migration of Modern Humans out of Africa was blocked for thousands of years by the Neanderthals in Europe and the Middle East.

I'm working on the same book. Only up to about chapter 3 at the moment.

I think I learned of it on one of your threads.

By the way, the Oppenheimer migration map has been superseded by new information in two instances that I know of. Haplogroups A and one haplotype of D seem to stem from one or more early coastal migrations running from Alaska down the California coast, most likely using watercraft. Haplogroup B, and the other haplotype of D, apparently traveled through the interior of the continent before reaching the west coast.

Things are changing very quickly in mtDNA studies! This information is new, from late 2006.

[blam]

"1. If humans arose from more primitive animals, why just in one spot near the equator? Why didn't the monkeys we came from migrate first? "

Some early ones did migrate before Modern Humans.

Strangers In A New Land

Image: JOHN GURCHE PORTRAIT OF A PIONEER With a brain half the size of a modern one and a brow reminiscent of Homo habilis, this hominid is one of the most primitive members of our genus on record. Paleoartist John Gurche reconstructed this 1.75-million-year-old explorer from a nearly complete teenage H. erectus skull and associated mandible found in Dmanisi in the Republic of Georgia. The background figures derive from two partial crania recovered at the site.

[Vn_survivor_67-68]

yeah yeah yeah........all of which means that the human species started in just one place on the earth. (and to justify THAT, they point to leakey who just "happened" on a skull that was waiting on a rock out in the weather for sll those centuries, LOL)

Instead of making up stories, "scientists" should be building omni's, so people could see for themselves.

"Scientists" are the most serious grifters in this world, as regards the past and future. They love to build on questionable, postulated, and false premise.....

[Coyoteman]

This raises 3 fundamental questions for me that I pose to any anti-creationism person:

1. If humans arose from more primitive animals, why just in one spot near the equator? Why didn't the monkeys we came from migrate first?

2. I'm pretty sure C14 dating is not accurate for samples over 40,000 years old (its actually never been proven accurate for samples over 2000 years old) so this is based on archeological evidence for the 80,000 years ago mark? How do you know that the flood did not skew these results...

3. DNA is DNA wherever it is in the cell, it is extremely susceptible to damage and mitochondrial DNA is especially conserved through species and even more within the human race. If you are using this to track migration, its more likely that you're seeing different results from mutation than place of origin...

I'll take a whack, though I am a scientist not an "anti-creationism person":

1. Monkeys didn't migrate because that would mean leaving the forests, to which they had adapted tens of millions of years ago. Humans are descended from apes who were squeezed out of the African forests when climate change reduced the size of the forests something like 5 or 6 million years ago. Over time they adapted to savanna conditions, developed bipedal locomotion, and thus were able to spread out where monkeys and apes were not.

2. Carbon 14 dating goes back some 50,000 years. It has been shown to be accurate through tree ring dating and calibration in various parts of the world. In the US it has been calibrated against tree rings from standing deal bristlecone pines past 12,000 years ago. In the old world it has been extended even older using tree rings and glacial varves. Thus, it has been shown to be accurate past 2,000 years. As for the "global flood" -- there is no scientific evidence for any such flood. That is a religious belief. (If you have any specific questions on Carbon 14 dating let me know, as I do a lot of it.)

3. There are areas in mitochondrial DNA (which is made up of 16,568 base pairs) in which slight changes are significantly more common. These are called the hypervariable regions. Most mtDNA studies on humans use what are now called HVR-1 and HVR-2. Specific mutations are passed on to all female descendants, and allow populations to be tracked through time. As an example, one individual from southern Alaska, dated to 10,300 years ago, was found to have a particular haplotype of haplogroup D; that haplotype has been found in living individuals from British Columbia to the tip of South America. I have another case of basal haplogroup A dating from 5,300 years ago being found in living individuals in California.

Hope this helps.

[Extremely Extreme Extremist]

"I got my reins down in A-a-africa."

[blam]

"By the way, the Oppenheimer migration map has been superseded by new information in two instances that I know of."

I love it. Its and indication of the pace of discovery.

"I'm working on the same book. Only up to about chapter 3 at the moment."

I'm in the middle of chapter nine. It's a better book than I originally expected.

My next books to read are:

1. OriginsOf The British, Oppenheimer

2. The Maya(seventh edition), Michael Coe.

[skippermd]

Thanks! No one has ever cited that before for me

[Don Joe]

Changing Climate

The authors of the new study believe that before reaching the Levant, migrating humans may have paused at the Persian Gulf for some time because of a hostile climate.

I didn't realize they had cars that early, the inconsiderate bastards!

[kinoxi]

3. There are areas in mitochondrial DNA (which is made up of 16,568 base pairs) in which slight changes are significantly more common. These are called the hypervariable regions. Most mtDNA studies on humans use what are now called HVR-1 and HVR-2. Specific mutations are passed on to all female descendants, and allow populations to be tracked through time.

Do you disagree with the link in post #7? Especially the part about paternal transference of mitochondrial DNA. It seem to debunk the entire theory if it is not an exclusively female phenomenon.

[Drammach]

RE: Sundaland as Atlantis...

I would go along with a tradition / mythology of Sundaland as "Mu", but not Atlantis..

Atlantis, if indeed it did exist literally, was almost definitely Santorini..
But as a culture, I believe the Atlanteans were more likely Santorini, Crete, Cyprus, Malta, etc... A seafaring, Island dwelling society built on trade..
The Pillars of Hercules referred to are the ancient ones in the Mediterranean, not the gateway to the Atlantic..
The people mentioned by the Egyptians were the "sea people", which were eventually dispersed throughout the Mediterranean and along the coast of Spain.. ( later referred to as Philistines, possibly Phoenicians, later, Canaanites )

Mu, on the other hand, was more ancient, and far larger.. I would be more inclined to believe that Sundaland / Mu are the same..
There may have been some confusion of legends, blending aspects of the two civilizations, or possibly legend through descent.. ( Atlantean civilization descended from survivors of Sundaland / Mu culture(s) ...
This might account for the erroneous timeline in which Plato claims Atlantis was 10,000 years old... ( in his time)
This may have been a reference to where the Atlanteans came from.. An ancient, 10,000 year old civilization that once thrived in Ice Age Indonesia/Sundaland...
Having migrated to the Mediterranean some 7,000 years ago, their advanced culture would have been able to establish itself with virtually no resistance on the islands, and eventually rule the Mediterranean basin for a couple thousand years before any seriously civilized culture could advance enough to threaten them..
If they had remained peaceful traders they might have been able to survive, but "good living" turned them to practice of slavery.. ( or local influences, who knows ?? )
They would have eventually been overwhelmed by sheer numbers anyway, but natural disaster quickened their demise...

Anyways, that's my 2 cents worth..

[Coyoteman]

Do you disagree with the link in post #7? Especially the part about paternal transference of mitochondrial DNA. It seem to debunk the entire theory if it is not an exclusively female phenomenon.

I'm not an expert in the field, but from what I have seen the evidence suggests that this type of transference could be quite rare.

The examples I cited 1) from southern Alaska (On Your Knees Cave) of an individual dated to 10,300 years ago being associated with numerous living individuals of the same haplotype, and 2) from California spanning 5,300 years, suggest that the standard model of mitochondrial descent is dominant. While there may be some cases of paternal transference, the examples I cited where the mtDNA is identical for many thousand years suggests that no such paternal transference occurred in those instances.

This may be in instance where they are still working out some of the fine points, but the overall pattern of mtDNA descent is well established?

But, things are changing quickly so we'll see.

[blam]

"I would go along with a tradition / mythology of Sundaland as "Mu", but not Atlantis.. "

Where Was Atlantis? Sundaland Fits The Bill, Surely

[SunkenCiv]

Thanks Blam.

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[kinoxi]

I wasn't aware that the field was mature enough to be established as fact. Even a rare paternal transference however would dispute the foundation of mitochondrial DNA dating. It is the prime assumption that it does not happen. I'm not disputing the general assumptions that prehistoric man migrated en masse. I just don't trust the methodology behind mitochondrial DNA analysis pertaining to the subject.

[Coyoteman]

I wasn't aware that the field was mature enough to be established as fact. Even a rare paternal transference however would dispute the foundation of mitochondrial DNA dating. It is the prime assumption that it does not happen. I'm not disputing the general assumptions that prehistoric man migrated en masse. I just don't trust the methodology behind mitochondrial DNA analysis pertaining to the subject.

Some things in the field can be considered facts, others are hypotheses or theory (the best explanations based on the available facts).

It is a fact that the individual in On Your Knees Cave had the same haplotype as individuals spread along the west coasts of North and South America, all the way to Tierra del Fuego.

It is a fact that this individual was about 10,300 years old, while the others were living individuals. I don't at this point know of any ancient samples in between these ages (repatriation laws make obtaining ancient DNA samples very difficult in California), but the field is young and growing rapidly. It is an hypothesis that the living individuals are descended from the ancient individual or his lineage. But it looks like a pretty safe bet.

If there was a small amount of paternal transference, what would that mean?

We are dealing with very small "founding" populations spreading around the world.

Because of this, paternal transference would usually mean the passing on of another sequence from the same population (the father's rather than the mother's). If the populations are relatively homogeneous this would not result in any significant changes.

However, if there were extreme differences between the males and the females in a population this could result in a significant difference in the descendants if paternal transference errors also occurred. Instances where men from one group raided an unrelated group to steal women and the resulting offspring were subject to paternal transference errors would be an example.

These examples suggest that the likelihood of paternal transference being a significant factor is limited.

I think it is safer to look at the preponderance of the evidence before you consider the long-odds evidence. It doesn't always work out that way, but if you're a betting man/woman that's usually the way to bet.

[kinoxi]

I don't see enough of a volume of information over time to substantiate the theory. I also don't see the initial assumptions to base the mutation timeline on to be valid at all. If I were a betting man I'd sit this one out and wait for more info.