globeandmail.com: Mammoth dung melting
http://www.theglobeandmail.com/servlet/story/RTGAM.20070917.wdung0917/BNStory/Science/home
"When the organic matter left behind by mammoths and other wildlife is exposed to the air by the thawing permafrost, his theory runs, microbes that have been dormant for thousands of years spring back into action."