Post by djoser-xyyman on Aug 5, 2010 12:10:59 GMT -5
Let's reverse the question: Why didn't Neanderthal enter Africa?
====
Why did modern human populations disperse from
Africa ca. 60,000 years ago? A new model
Paul Mellars*
Department of Archaeology, Cambridge University, Downing Street, Cambridge CB2 3DZ, England
Edited by Ofer Bar-Yosef, Harvard University, Cambridge, MA, and April 10, 2006 (received for review December 23, 2005)
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.
archaeology DNA modern humans Palaeolithic
=====
Our understanding of the origins
of modern human populations
(i.e., Homo sapiens) has made
massive strides in the past two
decades. We now know from studies of
both the DNA patterning of present-day
world populations and surviving skeletal
remains that populations that were essentially
‘‘modern’’ in both a genetic and an
anatomical sense had emerged in Africa
by at least 150,000 years ago (1–7). We
also know that these populations had dispersed
from Africa to most other parts of
the world by at least 40,000 years ago,
where they demographically replaced the
preexisting ‘‘archaic’’ populations, such as
the European Neanderthals (1–3, 8–19).
However, some of the most central
questions as to exactly how and why this
dramatic population dispersal and replacement
took place have never been
clearly resolved.
Two critical issues are posed by this
recent research. First, if we now know
that populations that were essentially
modern in both genetic and anatomical
terms had already emerged in Africa by at
least 150,000 years ago, why did it take
these populations a further 100,000 years
to disperse to other regions of the world
(1, 2, 8, 10–12)? And second, what were
the crucial evolutionary and adaptive developments
that allowed these populations
to colonize a range of entirely new and
alien environments and to successfully
compete with, and replace, the long-established,
and presumably well adapted, archaic
populations in these regions (2, 8,
13, 14, 17)?
The main problem posed by this scenario
at present lies in the sparsity of
well documented and well dated archaeological
evidence for the early modern
human colonization of Asia prior to ca.
45,000 B.P., when we know that early
colonists had reached parts of northern
and southern Australia, best represented
by the archaeological and skeletal finds
from Lake Mungo in New South Wales
(98–100). But clearly the spotlight is
now directed strongly onto southern
Asia to secure more direct evidence for
this hypothetical early dispersal route
(101, 102). Future discoveries in both
mitochondrial and Y chromosome DNA
research and, above all, archaeology, are
awaited to provide the crucial tests for
this hypothesis of the origins and dispersal
of our own species (103).
====
Why did modern human populations disperse from
Africa ca. 60,000 years ago? A new model
Paul Mellars*
Department of Archaeology, Cambridge University, Downing Street, Cambridge CB2 3DZ, England
Edited by Ofer Bar-Yosef, Harvard University, Cambridge, MA, and April 10, 2006 (received for review December 23, 2005)
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.
archaeology DNA modern humans Palaeolithic
=====
Our understanding of the origins
of modern human populations
(i.e., Homo sapiens) has made
massive strides in the past two
decades. We now know from studies of
both the DNA patterning of present-day
world populations and surviving skeletal
remains that populations that were essentially
‘‘modern’’ in both a genetic and an
anatomical sense had emerged in Africa
by at least 150,000 years ago (1–7). We
also know that these populations had dispersed
from Africa to most other parts of
the world by at least 40,000 years ago,
where they demographically replaced the
preexisting ‘‘archaic’’ populations, such as
the European Neanderthals (1–3, 8–19).
However, some of the most central
questions as to exactly how and why this
dramatic population dispersal and replacement
took place have never been
clearly resolved.
Two critical issues are posed by this
recent research. First, if we now know
that populations that were essentially
modern in both genetic and anatomical
terms had already emerged in Africa by at
least 150,000 years ago, why did it take
these populations a further 100,000 years
to disperse to other regions of the world
(1, 2, 8, 10–12)? And second, what were
the crucial evolutionary and adaptive developments
that allowed these populations
to colonize a range of entirely new and
alien environments and to successfully
compete with, and replace, the long-established,
and presumably well adapted, archaic
populations in these regions (2, 8,
13, 14, 17)?
The main problem posed by this scenario
at present lies in the sparsity of
well documented and well dated archaeological
evidence for the early modern
human colonization of Asia prior to ca.
45,000 B.P., when we know that early
colonists had reached parts of northern
and southern Australia, best represented
by the archaeological and skeletal finds
from Lake Mungo in New South Wales
(98–100). But clearly the spotlight is
now directed strongly onto southern
Asia to secure more direct evidence for
this hypothetical early dispersal route
(101, 102). Future discoveries in both
mitochondrial and Y chromosome DNA
research and, above all, archaeology, are
awaited to provide the crucial tests for
this hypothesis of the origins and dispersal
of our own species (103).