This geologist literally jumped to prove this point: 

“Over the last 100,000 years of the Ice Age cycling, we have had a couple dozen of these large, abrupt, widespread climate shifts, almost as if the Earth was bungee jumping off the climate roller coaster,” Richard Alley

Earth: The Operator’s Manual

Look- the tibia of a mastodon!

The story of a bulldozer operator who discovered a mammoth (get it?) trove of bones from ice age mammals, including mammoths, ground sloths and mastodons. 

-TG