The Altai-Sayan mountain region had no solid glacial sheet
during the Ice Age (Gerasimov and Markov 1939), although a chain of mountain glaciers factored into the isolation of northern and southern moose populations in this area.
Vast glacial sheets
blanketed much of the northern United States, Canada, and Europe, covering more than 10 percent of the northern hemisphere.
But the glacial sheets did not exist during the warm Eemian, so experts have had to look elsewhere to explain the fast changes then.
Charles and his colleagues thus suggest that the isotopic blips during the ice age largely reflect changes in atmospheric flow patterns spurred by waxing and waning of the glacial sheets in North America and Europe.
Named after Yugoslav/an mathematician Milutin Milankovitch, the theory holds that wobbles in Earth's orbit set the pace for the growth and disappearance of the great glacial sheets
that have spread over parts of North America, Asia, and Europe every hundred thousand years or so.
The two researchers suggest that a greenhouse warming may bring the same sort of conditions that stimulated the growth of glacial sheets
120,000 years ago.
This is how Denmark or Detroit must have looked during the last ice age, when thick glacial sheets
covered much of Europe, Asia and North America.
These findings supported a newly ascendant theory, which held that modern humans migrated from Africa to the Middle East and then spread throughout the world, while Neandertals -- possibly a separate Homo species -- entered the Middle East from Europe, perhaps as refugees from advancing glacial sheets
, only to bite the dust as modern H.
These cold-loving species, called glacial relicts, have inhabited the lakes since the retreat of the glacial sheets
at the end of the most recent ice age, some 10,000 years ago.
Ecologists view the modern world as an arena of continual change, especially without the last 2 million years as a series of ice ages have sent huge glacial sheets
sweeping periodically back and forth over much of North America, Europe and Asia.