posted
Why did modern human populations disperse from Africa ca. 60,000 years ago? A new model by Paul Mellars Department of Archaeology, Cambridge University, Downing Street, Cambridge CB2 3DZ, England
Published online before print June 13, 2006 Proc. Natl. Acad. Sci. USA
ABSTRACT:
Recent research has provided increasing support for the origins of anatomically and genetically "modern" human populations in Africa between 150,000 and 200,000 years ago, followed by a major dispersal of these populations to both Asia and Europe sometime after ca. 65,000 before present (B.P.). However, the central question of why it took these populations 100,000 years to disperse from Africa to other regions of the world has never been clearly resolved. It is suggested here that the answer may lie partly in the results of recent DNA studies of present-day African populations, combined with a spate of new archaeological discoveries in Africa. Studies of both the mitochondrial DNA (mtDNA) mismatch patterns in modern African populations and related mtDNA lineage-analysis patterns point to a major demographic expansion centered broadly within the time range from 80,000 to 60,000 B.P., probably deriving from a small geographical region of Africa. Recent archaeological discoveries in southern and eastern Africa suggest that, at approximately the same time, there was a major increase in the complexity of the technological, economic, social, and cognitive behavior of certain African groups, which could have led to a major demographic expansion of these groups in competition with other, adjacent groups.
It is suggested that this complex of behavioral changes (possibly triggered by the rapid environmental changes around the transition from oxygen isotope stage 5 to stage 4) could have led not only to the expansion of the L2 and L3 mitochondrial lineages over the whole of Africa but also to the ensuing dispersal of these modern populations over most regions of Asia, Australasia, and Europe, and their replacement (with or without interbreeding) of the preceding "archaic" populations in these regions.
Posts: 1549 | From: California, USA | Registered: Jan 2006
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One should do the same for all information. We will never know the exact reason for the dispersal from the Mother, but using the modern reasons for leaving one place to relocate to another is based on survival, be it: 1. Environment (continental disaster/shift/earthquake) 2. Climate (too hot/cold) radical change(s) 3. Tribal (war, conflict, shunning, etc) 4. Combiantion of all three having to do with a more efficient way to control events and escape the ways and form one's own!
Posts: 1290 | From: usa | Registered: May 2005
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quote:Originally posted by Myra Wysinger: Why did modern human populations disperse from Africa ca. 60,000 years ago? A new model by Paul Mellars Department of Archaeology, Cambridge University, Downing Street, Cambridge CB2 3DZ, England
Published online before print June 13, 2006 Proc. Natl. Acad. Sci. USA
ABSTRACT:
Recent research has provided increasing support for the origins of anatomically and genetically "modern" human populations in Africa between 150,000 and 200,000 years ago, followed by a major dispersal of these populations to both Asia and Europe sometime after ca. 65,000 before present (B.P.). However, the central question of why it took these populations 100,000 years to disperse from Africa to other regions of the world has never been clearly resolved. It is suggested here that the answer may lie partly in the results of recent DNA studies of present-day African populations, combined with a spate of new archaeological discoveries in Africa. Studies of both the mitochondrial DNA (mtDNA) mismatch patterns in modern African populations and related mtDNA lineage-analysis patterns point to a major demographic expansion centered broadly within the time range from 80,000 to 60,000 B.P., probably deriving from a small geographical region of Africa. Recent archaeological discoveries in southern and eastern Africa suggest that, at approximately the same time, there was a major increase in the complexity of the technological, economic, social, and cognitive behavior of certain African groups, which could have led to a major demographic expansion of these groups in competition with other, adjacent groups.
It is suggested that this complex of behavioral changes (possibly triggered by the rapid environmental changes around the transition from oxygen isotope stage 5 to stage 4) could have led not only to the expansion of the L2 and L3 mitochondrial lineages over the whole of Africa but also to the ensuing dispersal of these modern populations over most regions of Asia, Australasia, and Europe, and their replacement (with or without interbreeding) of the preceding "archaic" populations in these regions.
This study is actually quite progressive in denoting that so called 'modern behavior' began within Africa and led to population expansion within Africa and the *subsequent* habitation of the rest of the planet by these African modern humans.
Recent archaeological discoveries in southern and eastern Africa suggest that, at approximately the same time, there was a major increase in the complexity of the technological, economic, social, and cognitive behavior of certain African groups.
Note: Pre OOA Africans are correctly denoted above, as Africans, and not as Eurasians - protoEurasians, proto-caukazoids or any other form of lie, in the service of Euroecentrism. Note too the inclusion of 'southern' and Eastern Africa. It is in south Africa that some of the earliest artifacts suggesting modern behavior have been found - much to the chagrin of Eurocentrists.
could have led not only to the expansion of the L2 and L3 mitochondrial lineages over the whole of Africa
Here note: L2 and L3, not just L3.
Last legs - Eurocentrism, tried the line that 'only L3' and it's downstream lineages were forebearers of 'modern behavior'.
This should be understood as Eurocentrism's forced retreat from the preferred claim that modern behavior began in Europe - with the Cro-Magnon.
In this final gasp, African may have invented modern behavior [so called], but it would have began amongst 'only' the 'special group' of Africans who were ancestral to Eurasians - denoted by L3 downstream markers that make up essentially all non-African lineages.
Mellars study strikes another blow against this notion by implicating L2 and L3 in modern behavior.
Combined L2x and L3x make up most of the lineages in modern AFrica, and L1 is the parent of both L2 and L3. So the inclusion of L2 lineage is the key point here.
Lastly....
the ensuing dispersal of these modern populations over most regions of Asia, Australasia, and Europe, and their replacement (with or without interbreeding) of the preceding "archaic" populations in these regions.
Archaics in "these regions" here references native Eurasian and Australian hominids - Neanderthal, Erectus, etc..
There is no mention or conception in this abstract of archaic "Africans".
Thus as with the recent studies by Brace, and others, this study appears to deal another blow to Eurocentrism.
Equally significant in these sites is the evidence for the largescale distribution or exchange of both high-quality stone for tool production and the recently discovered shell beads from the Blombos cave, in both cases either transported or traded over distances of at least 20–30 km (31, 39).
All of these features show a striking resemblance to those which characterize fully modern or ‘‘Upper Palaeolithic’’ cultures in Europe and western Asia, which first appeared with the initial arrival of anatomically and behaviorally modern populations at 45,000–50,000 B.P., i.e., some 20,000 years later than their appearance in the African sites.
- Blombos cave is in South Africa.
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quote:Why did modern human populations disperse from Africa ca. 60,000 years ago?
Because they could. If they could migrate to different spots on the continent, they could migrate outside the continent as well (not that they would noticed; they didn't have maps back then).
posted
^ Yes but the question that is really being asked is why they were so successful, spreading out all over the globe and replacing previous hominids, suddenly and at one particular point in time.
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posted
Studies of both the mitochondrial DNA (mtDNA) mismatch patterns in modern African populations and related mtDNA lineage-analysis patterns point to a major demographic expansion centered broadly within the time range from 80,000 to 60,000 B.P., probably deriving from a small geographical region of Africa.
Not unreasonable, considering there were multiple migrations since, and even before that timeframe. This "before" scenario would of course, include the predecessors of anatomical modern humans; however, there is no reason to doubt anatomical moderns migrated out or attempted to migrate out of the continent prior to the said timeframe. Templeton seems to be among the few out there who doesn't necessarily stick with the "magical" era of about 60k years ago.
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posted
Relates to some earlier threads as well on the findings at Blombos cave and the notion of what defines 'modern behavior'.
Bombos cave modern behavior precedes the famous cromagnon by as much as 40 thousand years.
Also:
The final, and most controversial, issue atpresent is exactly when and how these anatomically and genetically modern populations first spread from Africa to other parts of Asia and Europe. Here there are two main possibilities. The first is that the initial expansion occurred via North Africa and the Nile valley, with subsequent dispersals to both the west into Europe and to the east into Asia (69 –71, 78, 94, 95).
The second is that the initial dispersal was from Ethiopia, across the mouth of the Red Sea, and then either northward through Arabia or eastward along the south Asian coastline to Australasia the so-called ‘‘southern’’ or ‘‘coastal’’ route (28, 69, 70, 96). The strongest evidence at present for the second hypothesis is provided by the mtDNA lineage-analysis patterns.
These point strongly to the conclusion that there was only a single (successful) dispersal event out of Africa,represented exclusively by members of the L3 lineage and probably carried by a relatively small number of at most a few hundred colonists (2, 8, 28, 97). This lineage rapidly diversified into the derivative M,N, and R lineages, which are particularly well represented in modern Asian populations and which are stimated to have arrived and diversified further in southern Asia by at least 50,000 B.P. and possibly as early as 65,000 B.P. in Malaysia and the Andaman islands (8, 9, 28, 97).
A similar conclusion has been drawn from recent studies of the Y chromosome evidence (97). This evidence would also conform well with the clear peak in the mtDNA distributions of Asian populations, dated broadly to 60,000 B.P. (23–25) (Fig. 1). This model, of course, would mean that the subsequent dispersals of anatomically and behaviorally modern populations into southwest Asia and Europe must have reached these areas substantially later, via western or central Asia (2, 8, 97).Posts: 15202 | Registered: Jun 2004
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posted
^ Single dispersal theory and southern migration route are both very unpopular with Eurocentists.
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posted
...although, I'm not sure how going with the North African/Nile Valley route changes anything about the point of origin of those migrants, being from the "south" [in tropical Africa].
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posted
It wouldn't literally, but it would potentially give Europeans a separate group of African ancestors from native South Asians, Melanesians, Australians and other tropically adapted and [melanodermic], Black populations.
Instead we are left to confront the fact that leucoderm, and cold adapted phenotypes did not exist at this time.
The European phenotype and it's trivial physical distinctions are but and evolutionary adaptation to low UV conditions, and cold weather in Northern Eurasia.
Existing genetic and skeletal evidence suggests that these adaptions could not have occured prior to 30 thousand ya, or elsewhere other than Northern Eurasia.
Moreover these phenotypes would not have reached present levels far prior to the mesolithic - 12000 ya~.
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quote:Originally posted by rasol: It wouldn't literally...
Exactly.
As far as the issue of having "separate group of African ancestors" is concerned, “indigenous” European gene pools are largely a derivative and subset of Eurasian gene pools, not precluding ongoing gene flow directly from Africa. The above mentioned citation makes a good point on this:
"These point strongly to the conclusion that there was only a single (successful) dispersal event out of Africa,represented exclusively by members of the L3 lineage and probably carried by a relatively small number of at most a few hundred colonists (2, 8, 28, 97)."
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Based on the archaeological dates for Mt Toba ash (74kya as established by potassium argon) and Australian paintings (>60kya as confirmed by silica luminescence), the migration date must precede 60kya.
An 85kya date is suggested by one interdisciplinary methodology involving genetics, archaeology, geology, anthropology, and climatology.
posted
This latest study is consistent with various physical and genetic studies that have been accumulating for the past couple of decades:
The oldest Out of Africa expansion occurred 65,000 +- 23000 years ago and is witnessed by mtDNA descendants preserved in Papua New Guinea; the Papuan node is derived from a Eurasian founder, we tentatively propose the following scenario to account for the obvious phenotypic differences between Papuans and [Northern] Eurasians despite their *sharing a common ancestry:*
"They derive from a single African migration, but split at an early stage before reaching Europe. Meanwhile, proto-Eurasians spent 20 or more millennia genetically drifting to their present distinct phenotypes." - Peter Forster, Antonio Torroni, Colin Renfrew and Arne Röhl
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Anatomical/behavioral modern humans originated only in Africa.
A/BM human artifacts lay beneath Toba ash.
A/BM humans left Africa long enough ago to make their way to India/SE Asia.
Any date earlier than Mt Toba's eruption is too late for the successful Homo sapiens OoA migration.
The similar model holds true for the other evidence brought under consideration in the previously provided links, qv.
Unless that information is false, Hss left Africa well before 60kya.
Posts: 8014 | From: the Tekrur in the Western Sahel | Registered: Feb 2006
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quote:Any date earlier than Mt Toba's eruption is too late for the successful Homo sapiens OoA migration.
I assume you mean any date -later- than Toba is too late, otherwise the sentense is contradictory.
Anyway, the post of the Forster Torroni study is not meant to contradict you over a minor dating issue, but rather to expound on southern migration/single migration theory.
I don't think there is much 'issue' within the 75kya vs. 60kya estimates.
Note: if we literally insist on 80kya or earlier there are problems.
L3 itself is often estimated at around 70kya~.
Toba's eruption dating is also and *estimate*,
All non Africans have post L3 lineages.
Any date earlier than L3 is by definition - too early to be ancestral to L3x modern non Africans.
quote:Hss left Africa well before 60kya.
Yes we know this.
As pointed out by Paul Mellars:
One aspect of the current evidence that is potentially highly informative in this context lies in the evidence for a precocious and apparently short-lived expansion of anatomically modern populations from northern Africa into the immediately adjacent areas of southwest Asia at 110,000–90,000 B.P.
...but the ancestors of current non-africans are *not* considered the 1st HSS.
In fact, they aren't. Because there is no L3 at this time.
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posted
^^Undoubtedly, pertaining to the last point. Anatomically modern human migrants who had lineages pre-dating the L3, [who would have likely been in very small numbers in any new locales outside Africa] would have largely been replaced, as is the case with the more archaic hominids like the Homo Erectus or Neanderthals, by the expansions accompanying L3 and M168 lineages; expansions which are deemed more successful, for instance, judging by the exclusive representation of L3 mtDNA derivatives in all modern non-African groups, in the extra-African regions sampled thus far.
-------------------- Truth - a liar penetrating device! Posts: 5964 | Registered: Jan 2005
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Yes I meant after Toba's eruption, thanks for the precision.
As I plainly wrote "first successful Homo sapiens OoA migration", there's no need to confuse things by intimating the unsuccessful Qafzeh/Skhul Hss migration which has nothing to do with the peopling of Asia Europe and the Americas.
I'll stick with the date I favor as its eggs are in more baskets (multi-disciplinary based) than just the proposed L3x date (single discipline).
And for the record, yes, all these dates are an *estimate*.
Posts: 8014 | From: the Tekrur in the Western Sahel | Registered: Feb 2006
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posted
Fair enough, but note that Mellars work is also multi-disciplinary, and he is well aware of the Toba eruption, and the various and very different theories associated with it, including the idea that so called modern behavior was somehow 'caused' by post-toba eruption and climate change.
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posted
Now of course, when one talks of "successful" anatomically modern human migrations, it should be reiterated that it is not the "migration" itself that is being assessed, which even the likes of Homo Erectus has been able to accomplish, not to mention colonizing new locales outside of Africa - rather, here it is to assess not only the ability to colonize the greater part of the globe, and expand into large populations, but also to expand to the point of ultimately outnumbering and even replacing the precedessors in the new found locales.
-------------------- Truth - a liar penetrating device! Posts: 5964 | Registered: Jan 2005
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And of course, if successful means provably relevant to current populations, you are still tied to a post L3X time frame.
Original Non African migrants.
Homo Sapiens Sapiens.
"Modern behavior".
3 distinct issues.
Homo Sapiens Sapiens is and anatomical/species classification that arguably dates back as far Herto Man in Ethiopia at 150 kya.
Modern behavior - is a judgement call - that Wellars thinks dates back to east and south Africa prior to OOA outmigration and is causal to said migration.
"Successful" OOA migration is too subjective, but most coherently amounts to "L3x lineage" because that's what modern non-Africans are.
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The European phenotype and it's trivial physical distinctions are but and evolutionary adaptation to low UV conditions, and cold weather in Northern Eurasia.
Existing genetic and skeletal evidence suggests that these adaptions could not have occured prior to 30 thousand ya, or elsewhere other than Northern Eurasia.
Moreover these phenotypes would not have reached present levels far prior to the mesolithic - 12000 ya~.
quote:
Do you have a source for this? I am interested
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