New Scientist is a touch fuzzy. Best to stick with Science and Nature
for serious discussion. It is not bad. It simply does not have the
caution and rigor of the others.
Notice the out of Africa map
http://www.newscientist.com/data/images/ns/cms/dn22277/dn22277-2_834.jpg
is dated not reflecting the modern size of the Red Sea not the size
during the ice age. In fact all of it is modern coast lines instead of
ice age ones. The obvious misrepresentation is the brown patch showing
travel to Australia. That Brown patch was dry land all the way to about
the last 50 miles to the Australian coast. But the words in the brown
patch call it island hopping.
The problem with the modern coast line is showing the route out going
all the way down the Nile and crossing through the Sinai and without
explanation not heading north up the east coast of the Med. The
arrowhead of that path does show the established branching into Europe
and Northern Asia and the Americas. Redraw that path as directly across
the southern end of the Red Sea and not up the Nile and the rest of what
we know makes perfect sense including the re-entry of Caucasians into
northern Africa to become Egyptians.
To repeat, be careful with New Scientist. Read the author's name and
credentials first. This author has no credentials, just a science writer.
> Humans may have conquered the world, but not without a big
> helping hand from climate change. A major study of the last
> 120,000 years of history reminds us that, while we are
> adaptable, our species is ultimately at the mercy of the
> climate.
>
> Homo sapiens evolved in Africa around 200,000 years ago, but
> only left the continent about 70,000 years ago. After that
> our species rapidly went global, colonising first Europe and
> Asia, and then Australasia and the Americas.
>
> But why did early humans linger so long in Africa, and what
> spurred them to finally move? Several theories have been
> proposed, but according to a large effort to reconstruct
> the last 120,000 years of human history – including the
> climate we lived in and the vegetation we fed on – the
> current population spread around the planet would not be
> as it is without key changes in the climate.
> ...
Climate change, yes, but not in the modern political sense. There was
an Ice Age. The Red Sea was much smaller and possibly landlocked with a
land bridge connecting what is now east Africa with Arabia which would
not have been called a Peninsula back then. In the worst case people
could have migrated quickly up the west coast of the much small Red Sea
and back down the east coast.
As to why so long, good question however the "so long" is growing by
arbitrarily dating the first HSS earlier and fighting against moving the
exit date back. In the last decade I have watched the date of the
"first" HHS pushed from 120kya to 200 kya without the least supporting
evidence. I have found no papers discussing the push back of the date
which I would expect to be many papers debating the evidence but
nothing. Similarly I have read several papers discussing evidence of
being well into Arabia 80kya or so but all the mentions appear to
begrudge even 65 vice 60kya.
But even in the best case 120 to 80 that is still 40 ky before leaving.
The most obvious answer is population growth was slow and there was
competition from other hominids who, if we are any indication, were
nasty SOBs. Further we know next to nothing about their reproduction
rate or social organization which may have been more survival prone than
ours and only better weapons or something turned the tide.
In addition there was plenty of land in southern Africa to absorb a
growing population. Despite a popular mythology there is really no
evidence of people naturally exploring or heading off into the unknown
for the fun of it. People would not naturally expand until there was
more food for more people at the outer edge of expansion.
Beyond that there is much we do not know about the details of climate
and geography during the ice age which was not a constant but had minor
advanced and retreats. The glaciers would have largely remained but the
conditions for advancing and retreating would have had major impacts on
Africa and Arabia. It is just speculation but perhaps there was an east
African desert blocking northward travel, i.e. the Sahara was much
further south. Only with its retreat did people leave.
--
Anyone who thinks Amadinejad is a new Hitler
thinks Chaplin made a documentary.
-- The Iron Webmaster, 4413
http://www.giwersworld.org/israel/is-seg.phtml a14
Fri, Sep 28, 2012 4:25:32 PM