Just before the time of the Clovis people, about 12,000 years ago, the great ice
sheets that covered much of northern North America began to melt.  Within a few hundred years,
they had disappeared, leaving profound changes on the land.  Huge ice-dammend lakes burst fee
in gargantuan torrents, transforming grassy prairies into bald scablands.  Mountainous heaps of
soil and rocky debris were deposited by melting glaciers, and lakes dotted the lands formerly
covered by ice.  Everywhere the land rose, rebounding from the enormous weight of the mile-thick
ice.<P>
	. . .
	Not only were the great mammoth and mastodon doomed; also gone or fast disappearing
were the four types of giant ground sloths that lived then, including Rusconi's ground sloth, an
inhabitant of the Southeast that measured 20 feet in length and weighed some three tons.  In
addition, giant rodents, three species of camel, several species of four-pronged antelope, giant
bison, lumbering armadillolike glyptodonts, and tapirs that had roamed North America became
extinct.  So did such impressive carnivores as huge lions, cheetahs, saber-toothed cats, wolves,
tratorns--vulturelike birds with wingspans of up to 17 feet--and the giant short-faced bear.  And the
horse, which had originated in the Americas, perished along with these other North Americna
fauna, only to return with the Spanish invaders in the sixteenth century.<P>
	Large mammals, of course, still live in North America; grizzly, black, and polar bears;
wolves; cougars; elk, or wapiti; moose; musk oxen; mountain goats; bison; mountain and Dall's
sheeep; proghorns; caribou; whitetailed and mule deer.  But when the land groaned under the
weight of the great northern ice sheets, five time as many such animal species lived.<P>
......<A HREF="/biblio.html#rl">In the Age of Mankind</A>, p 167-168.
	Roger Lewin