I analysing the pollen and gas contents from ice shelves, it has been found
that when CO2 levels go down, grasses have an advantage over woody plants
such as trees.  This effect has also been shown in the lab where high CO2
levels cause rapid growth in woody plants while supressing the growth of
grasses. When this gas is reduced due to the uplifting of mountains,
tempetures also decrease due to a reverse greenhouse effect.  These periods
of low tempetures and high grass growth are called "ice ages".

The grasslands of the ice ages were most productive in what are known as the
Steppe-Tundra.  These bordered the ice sheets and because of their high
precipitation levels and long summers had one of the highest concentrations
of biomass ever found on earth.  This was the home of the Pleistocene
Megafauna which included mammoths, mastedons, giant camels, giant ground
sloths, giant bison and hundreds of other species which with the demise of
the grasses and the dominance of the forrest became extinct about 10,000
years ago.

Man may have accellerated this extinction.  It began when he joined with
dogs to become the dominant predator of the steppe-tundra.  Homo Sapiens who
had also evolved to occupy the steppe tundra and shared the dependence on
grass with his game also faced starvation in the advancing forrest.  Even
the most verdant rainforrests of today offer slim pickings for human food
when compared to the happy hunting grounds of the steppe tundra.

To survive, Man entered into a new partnership with grasses and the animals
who ate them.  This new partnership is called the Neolithic Revolution.

Ray Audette
Author "NeanderThin"
http://www.neanderthin.com