Since fossil vertebrates were first discovered at Porcupine Cave on the rim of South Park, Colorado, in 1981, the site has become the world’s most important source of information about animals that lived in the high elevations of North America in the middle part of the ice ages, between approximately one million and 600,000 years ago. Beginning in 1985, teams of scientists and volunteers from three major research institutions —the Carnegie Museum of Natural History, the Denver Museum of Nature and Science, and the University of California Museum of Paleontology—spent some 15 field seasons excavating and studying tens of thousands of fossil specimens that have opened a window onto past evolutionary.
