Ray Audette wrote:
>From: Amadeus Schmidt
>> I agree and can see that the ice age in northern areas (europe)
>> presented such a bottleneck for the humans in this areas.

Ray:
>The Ice Age was not the bottleneck as it was the norm for the last two
>million years, the entire span of existence of homo-sapiens (our type of
>hominids).
The last cold phase of the ice age, which begun ac about 30000 y.a.
have presented an evolutionary bottleneck for the Cro Magnon humans
which came in after 35000 to the colder northern europe areas.
Because large parts of europe were covered with a total ice shield
(total desert, like todays arctic). And in ice age winters
the rest of the land was covered without vegetation,
changing to green herbs (without trees) in summers.
Since the possibility to rely on plant sources was lost, this is
exately an extreme harsh bottleneck situation - in *europe*.
The worm phases were just as long and as worm as
the worm phase we are living in today.
With equal conditions and vegetation.
See time table below (1)
and map: http://www.esd.ornl.gov/projects/qen/lastgla.gif

The previous human genus which inhabited Europe before (neanderthals)
through several worm and cold phases (100k-200k years)
died out. Or have you seen one?

The invading humans "Cro Magnon" - our sure anchestors - existed in africa
according to the fossil record since about 100k-120k years.
Parallel in time and in different locations.

>The Ice age affected both northern and sourthern hemispheres,
>producing steppe-tundra and Pleistocene megafauna in both.  It was the
>rapid
>destruction of this habitat during the short interglacial periods (about
>10,000 years each) that produced the bottlenecks that would produce the
>future stock when the glaciers returned.

You draw a picture of humans "naturally" living in ice age glaciation
phases and from megafauna only.
For such, a worm phase without mammouths or even any
big animals would constitute the actual bottleneck
(like Australia, Neuginea, and the Americas were left).

But the successful ice age hunters
homo neanderthalensis and erectus) died out.
Sooner or later our anchestors come from a wormer climate and from
Africa. The situation in africa was different,
the cold phases destroyed most rain-forests
- our natural habitat for the eons before 2mio years ago.
They were changed to woodlands, dry grasslands or desert.
(see map at: http://www.esd.ornl.gov/projects/qen/NEW_MAPS/africa1.gif

The main difference to ice age europe - to consider nutrition - is:
If an area was habitable by humans at all (not to arid) then
there was always vegetation to live upon.
And the existing animals were probably *not* fat.
But nuts are.

>Common mutations found among
>stressed populations would include gracile forms and neotinized forms of
>Pleistocene megafauna.  Some of these are todays domestic animals.
>Ray Audette

And the more gracile form of human, emerging from a worm climate,
at last survived and replaced other "mega-humans" like neanderthals
even in the harshest, coldest areas (e.g. in Europe of 30000bc.)

Amadeus Schmidt

(1) time table for *europe*
from: http://www.esd.ornl.gov/projects/qen/nerc130k.html
(presents a very good introduction text to ice age climate too)

150,000 y.a. - cold, dry full glacial world
around 130,000 y.a. - rapid warming initiates the Eemian interglacial
130,000-110,000 y.a. - global climates generally warmer and moister than
present, but with progressive
cooling to temperatures more similar to present.
?110,000 y.a. - a strong cooling marks the end of the Eemian interglacial
105,000-95,000 y.a. - climate warms slightly but still cooler and drier
than present; strong fluctuations.
95,000 - 93,000 y.a. - another cooler phase similar to that at 110,000
y.a.
93,000 - 75,000 y.a. - a milder phase, resembling that at 105,000-95,000
75,000 - 60,000 y.a. - full glacial world, cold and dry
60,000 - 25,000 y.a. - 'middling phase' of highly unstable but generally
 cooler and drier-than-present conditions
25,000 - 15,000 y.a. - full glacial world, cold and dry;
 (includes the 'Last Glacial Maximum')
14,500 y.a. - rapid warming and moistening of climates in some areas.
 Rapid deglaciation begins.
13,500 y.a. - nearly all areas with climates at least as warm and
              moist as today's
12,800 y.a. (+/- 200 years)- rapid onset of cool, dry Younger Dryas in
many

areas
11,500 y.a. (+/- 200 years) - Younger Dryas ends suddenly,
back to warmth and moist climates (Holocene)

(2) key to the area descriptions in the following maps
http://www.esd.ornl.gov/projects/qen/adams3.html

(3) map of ice age africa
http://www.esd.ornl.gov/projects/qen/NEW_MAPS/africa1.gif

(4) for comparison: africa in a worm phase (like today and often)
http://www.esd.ornl.gov/projects/qen/NEW_MAPS/africa7.gif

(5) root of that excellent site on paleolithic climates
http://www.esd.ornl.gov/projects/qen/nerc.html

Thanks to John Adams :-)

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