" So when in the late 1980s Cann, Stoneking and Wilson
> (1987) published their analysis of mtDNA lineages purporting to show
>that >all modern humans were the descendants of a single female who
lived >somewhere between 60 and 200,000 years ago, anthropologists jumped
on
>the>bandwagon with vigor. This view is probably the most widely accepted
>view in >anthropology today. It is known as the Out of Africa(OoA)
hypothesis.
>Modern humanity, in this view,
No. The "out of africa hypothesis" is not the same as the
discreditied "Eve" hypothesis.
>Eve must have resided in Africa, and that the geographic distribution of
genes must
>reflect the total replacement of the archaic population. These
>predictionsof the Eve theory are testable.
>
Populations do not arise from single individuals. Species arise
from populations.
Glenn, I just couldn't read any further...
There is no question that all humans came out of Africa; the only
question is whether they came out only once or al least twice.
The single version (known as the "multiregional" or "candelabra" or
"menorah" view) posits that the original erectus diaspora from Africa,
now dated to just under two million years ago, established isolated
populations around much of the globe (the Western hemisphere excluded).
These isolated populations, often facing radically different
environmental conditions, nonetheless, according to this view, evolved
independently and simultaneously into the single surviving human species
we know today (sapiens sapiens). (There were other human species,
neanderthals for example, that did not survive and who became extinct
only some 30,000 years ago but were known to have lived in Asia and
Europe as far back as some 220,000 years ago.)
Until recently, the multiregional view was the more accepted view.
However, Darwin himself stated his belief that modern humans originated
in Africa.
At the time that Darwin wrote, the only human species known to exist was
*Homo sapiens*. The original "Neanderthal Man" was discovered only three
years before Darwin published his famous book, and no one knew what to
make of it at the time. (A Neandertal skull was discovered in Gibraltar
in 1848, but it wasn't analized until long after Darwin published.) The
first *Homo erectus* fossils were not found until 1891, but they were not
considered to be a species of *Homo* at the time.
But it is a bizarre view because it contradicts the basic rules of
evolution where isolated populations of a single species generally evolve
into different species in response to differing environments and their
resultant natural selection pressures.
To combat this obvious problem, defenders of the multiregional view had
to come up with the notion that although the populations were essentially
isolated, they were not totally isolated and there was a small but
sufficient amount of interbreeding among them to prevent the basic
speciation process from operating. This was also a bizarre view (a foot
mobile homo erectus in Indonesia is going to be interbreeding with
erectus populations in northern China and Europe? I don't think so). As
the holes in the multiregional view became larger and larger, support for
it began to dwindle.
However, others argue that this is not correct and that even in the
multiregional view, *Homo erectus* evolved into one species (us) or more
than one species (including us) so the "basic speciation process" had to
have been in operation--at least once.
The second version (known as the "Noah's Ark" or "Out of Africa" view)
posits that the original erectus diaspora from Africa, while showing the
extraordinary mobility and adaptability of these earliest humans, was
ultimately a failure and that these isolated populations eventually
became extinct (in like manner to the neanderthals).
But if the isolated populations became extinct, erectus in his homeland
of Africa did not, and in fact he continued to evolve into the tool
making habilis. Then at the end of the last ice age (roughly 250,000
years ago), one particular population of early humans in Africa spread
out behind the retreating ice sheets and repopulated the globe, creating
thereby the single human species we know today as sapiens sapiens.
First, *Homo erectus* did become extinct in Africa as well as
elsewhere,but not before giving rise to at least one other species (*Homo
heidelbergensis*?, archaic *Homo sapiens*?) which, in turn, gave rise to
at least one other species (*Homo neanderthalensis*?, *Homo sapiens*?).
Second, *Homo habilis* was the first human species and gave rise to at
least one other species (*Homo ergaster*?, *Homo erectus*?).
At any given point in time, there might be any number of species of the
same genus in existence, including ancestral ones. For instance, between
1.8 and 1.4 million years ago, three species of *Homo* might have existed
in Africa: *H. habilis*, *H. ergaster*, and *H. erectus*. And between
250,000 and 100,000 years ago, there might have existed three species of
*Homo* in Europe: *H. heidelbergensis*, archaic *H. sapiens*, and *H.
neanderthalensis*.
However, the prevailing view is that anatomically modern humans first
left Africa around 130,000 years ago. Second, instead of "repopulating
the globe", they replaced whatever previous human species still existed
when they arrived. Third, the "single human species" was created in
Africa before they left there
(maybe as much as 200,000 years ago), not after they had migrated out of
Africa.
This view comports with the basic principles of evolutionary theory
Cheers,
RLT
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